My grandmother yelled: “Those damned mosquitoes”. She grabbed the “FLIT”, she sprayed in every corner of the bedroom where I was ready to go to sleep. After “The Flit” I slept like a rose (Dutch-ism). I haven’t seen them for 50 years since the emergence of the modern spray can. As a memorial, you will find a small Cygwin / Linux script for exterminating “Thumbs.db” on your hard disk.

Put this in a file flit.sh somewhere, like desktop or home, make it executable and modify to taste…

#!/bin/bash
find /data \( -name 'Thumbs.db' -or -name 'desktop.ini' -or -name 'Thumbs.db:encryptable' -or -name '.DS_Store' \) -print0 | xargs -0 rm -rf

• find finds (recursive) the files between escaped parenthesis \(...\) and lists the files (print0) in directory /data. Output is piped to xargs that takes care of removal (rm). The zero’s deal with file names with spaces.
• It is one of many possible approaches, but what I like about this approach is that you can check output first, by running it in a shell without | xargs -0 rm -rf.
• A DOS batch file named flit.cmd could be something like:

@echo on
C:
cd /installers
del /s /q /f Thumbs.db desktop.ini .DS_Store Thumbs.db:encryptable
echo Finished FLIT.cmd
pause

It is always hard to come up with a system with cutting edge components without the accompanying problems and showstoppers. So this page can help you (and me), I hope you like it. This is in particular true for Linux users where unsupported hardware can be a nasty disappointment.

This page is pre published in order to process your input. So feel free to leave a much appreciated comment, below or here.

Ingredients

Before explaining why these specific components were chosen, here is a listing. One stop shopping was performed at Megekko.nl (for Belgium and Dutch readers):

• AMD Ryzen 5 PRO 4650G processor 3,7 GHz 8 MB L3 100-100000143MPK
• Asrock B550M-ITX/ac motherboard 90-MXBDH0-A0UAYZ
• Kingston DDR4 HyperX Predator 2x16GB 3200 HX432C16PB3K2/32
• Samsung 970 EVO 1TB M.2 2280 NVMe MZ-V7E1T0BW
• WD HDD 3.5″ 16TB S-ATA3 Gold WD161KRYZ
• Noctua NH-L9a-AM4 NH-L9a-AM4
• Existing NedCAD case plus Seasonic PSU and chassis fans
• Cherry Strait 3.0 USB keyboard JK-0350EU
• Logitech Mouse M500 910-003726

Rationale

You may ask yourself why to choose those components, so here is an explanation:

• About the CPU:
  • The base is Xubuntu. I often work with virtual machines (VirtualBox) for development, like Windwows 10. Having enough cores and performance is a must. AMD 4650G offers that.
  • I also do use BricsCAD and most CAD applications rely heavily on single thread performance. AMD 4650G offers that too.

• First of all, we recently started to use Asrock A300 systems with AMD Ryzen 5 3400G inside. They perform far beyond expectations. So, following the Ryzen abcdG APU path is obvious.

• Price performance ratio is an argument. It is about trying to find a balance without going too fancy, getting it over dimensioned and without shooting your legs because it doesn’t fulfil the needs. It also means trying to stick to Asrock’s QVL’s.
• The bulky bastard hard disk is needed for running rsnapshot, I use this machine to have an extra – extra back-up of our servers and in case of remote, off grid, operations I can get to our data. WD Gold series turned out to be fast and reliable over the past years.
• Why Asrock? Many years ago I was fed up with not getting proper support (Asus, hope it is better these days) so we changed to and standardized on Asrock. When you really run into serious trouble, they take their responsibility – although it can take some time and you may have to push a bit. So far, I am very happy with them.
• The motherboard Asrock B550M-ITX does mention AMD 4650G and Kingston HX432C16PB3 in the QVL and has an attractive price. All in all a balanced, tested and reliable mix.
• Cherry Stream – favourite – was not available, so Cherry Strait is an adventure. And about the mouse: After using the model for so many years my hand can’t handle any other shape anymore. Very personal and yes, all is wired too.

Caveats, do’s and dont’s

These listed points are discussed in detail later on.

• DDR4 memory modules are not properly recognized by the motherboard. While on the QVL, 2400 MHz was detected instead of 3200 MHz.
• The standard AMD Wraith CPU cooler interferes slightly with the memory modules. Finally I removed some of the plastic. The Noctua NH-L9a-AM4 is a better, but more expensive, choice.
• (X)ubuntu 20.10 returned kernel panics after presenting GRUB with a normal boot menu without offering options “try” or “install”.
• Xubuntu 20.04 left the system in a semi frozen state after an inactivity period.
• Xubuntu 20.04 fresh install left me with a not active sound card.
• Missing USB cable for the motherboard.

Conclusions

Preliminary…

General verdict: Above expectations in general. Proper price performance ratio. Highly recommended for general purposes, virtual machines. CAD performance is poor so far. Not sure what the cause of this is, working on that.

Fans: I found the AMD Stealth sound becoming annoying in time, it sounds like a humming transformer. The difference between the AMD Wraith Stealth and the Noctua NH-L9a-AM4 is day and night. Noctua NH-L9a-AM4 is much more silent without the irritating hum. The only drawback is its price tag and, in a far from your ears solution, Wraith Stealth does a proper job for a nice price.

Xubuntu: I did not manage to install Xubuntu 20.10. However, 20.04 does a great job, after solving the unresponsive keyboard and mouse issues. It is (as)rock solid. It is not a system without glitches but they all turned out to be solvable. It is a fast workhorse. In fact, I changed its name (/etc/hostname) to PharLap, so that you know!

Keyboards: Cherry makes fine instruments. My wife took possession over the Cherry Strait and loves it. Personally, Cherry Stream stays favourite. The reason for that is the standard lay out. Cherry Strait has a non standard area for insert|delete|home|end|page up|page down and despite trying, I couldn’t get used to it quickly.

USB connectors

In the manual is states:

There is one header on this motherboard. This USB 3.2 Gen1 header can support two ports.

Now, I need a cable… On reddit someone says:

You can thank the USB-IF standards body for that. They’ve made a complete mess of the naming
* USB 3.0 == USB 3.1 gen 1 == USB 3.2 gen 1
* USB 3.1 == USB 3.1 gen 2 == USB 3.2 gen 2
The connectors are Type A or Type C and can be used with any USB speed / version.
* Type A connectors are the traditional connectors that you know and love.
* Type C connectors are the new reversible connectors
Just because there is a Type C plug on a computer doesn’t mean it’s got a USB 3.2 gen 2 port.
The preferred consumer names from the USB-IF are actually SuperSpeed USB and SuperSpeed USB 10 Gbps. But nobody is following their direction.

Good to know, let’s find a cable from motherboard to front panel. Well, it turned out to be not too hard, just search for “USB 3.0 cable motherboard” on Chinese sites to get great offers. This came in:

And they are available in other configurations like brackets.

Installing Linux

Installing Xubuntu 20.10

This turned out to be NOT working, but for reference it is documented…

Where is “Startup Disk Creator” when you need one? Gone to oblivion? No, see next heading. So another approach after downloading Xubuntu… 20.10!

Put a USB stick in and ctrl-alt-t in order to find it…

sudo fdisk -l
...
Disk /dev/sdx: 7,25 GiB, 7776239616 bytes, 15187968 sectors
Disk model: DataTraveler G3 
...

Next, if you don’d have ddrescue, do apt install gddrescue on Ubuntu. Started in the directory where the iso lives and creating it on stick /dev/sdx – see output fdisk for your stick.

sudo ddrescue xubuntu-20.10-desktop-amd64.iso /dev/sdx --force -D
...

After finishing, you’re ready for the next step.

Well, not quite! Xubuntu 20.10 was a bad experience. Several attempts left the system with a kernel panic. Bummer! Sayonara Xubuntu 20.10!

Question: Is this smart? I.e. using ddrescue? synaptec searching for usb-creator is an option… More on that, if you have an opinion, please leave a comment. See https://help.ubuntu.com/community/Installation/FromUSBStick.

Installing Xubuntu 20.04

In the mean time, I found “Startup Disk Creator”. Turns out to be an alias, so if you can’t find it: apt install usb-creator-gtk first. A boot stick with an ISO of Xubuntu was a piece of cake, boot with the stick, press F11 after the keyboard LED flashes, more cake.

Partitioning

Not being used to UEFI, that still is a bit strange. What I did and in this order:

• GPT partition table
  • ESP (EFI System Partition): 0.2% ~ 2 000 MB. Is less a penny wise and a pound foolish?
  • EXT4 for /: 800 000 MB
  • SWAP: 32 000 MB
  • Not partitioned for emergency OS and so on: ~ 150 000 MB

No sound!

No sound, there is always something… pacmd list-cards offers an overview of all “cards” and both HDMI and onboard card resulted in: active profile: <off>. Bad news. Probably not necessary, but I plugged in some headphones, did sudo apt-get remove --purge pulseaudio and then sudo apt-get install pulseaudio, rebooted and I had the onboard audio working. Strange!

Solving mouse and keyboard semi frozen state

Mouse and keyboard work while you are busy. Then you grep a cup of coffee and find out the mouse pointer moves, but no click events from either mouse or keyboard arive. However you can do Ctrl-Alt-F1 and do your thing. Turning back with Ctrl-Alt-F7 and the problem is back. Pretty frustrating!

Finally, I removed the screensaver, when I leave my work space I turn off my monitor (and the lights).

Solutions are described on Askubuntu (if you need a screensaver go there) and the Xubuntu maillinglist. These are the steps I took:

sudo apt remove xfce4-screensaver

Next, disable start on login of xfce4-screensaver: In Xubuntu it is:
Whisker > Settings > Session and Startup > [] Screensaver (launch screensaver and locker program)

Then, Whisker > Settings > Power Manager > Tab Display > Display power management > ON (Yes, not OFF!) > move sliders to “Never”.

Finally:

xfce4-screensaver-command --exit

All kind of other installing stuff

I’ve written step by step instructions here, you may want to start at page 1:

AMD fan interferes with HyperX modules

Although not much, the fan housing hit the RAM module. In order to maintain proper contact of RAM in the slot, I removed some plastic from the fan housing. On top of that, I did not want it to start resonating.

The solution is easy, see the picture:

In addition, cleaning the aluminium with isopropanol and adding new thermal paste is necessary.

BIOS assigns inferior speed to Kingston RAM

The HyperX Kinston modules are 3600 MHz and the BIOS recognized them as 2400 MHz – or so it seems. I’ve changed that manually in the BIOS: B550M-ITX/ac P1.00.

So it turns out to be 2400 MHz RAM, verified for overclocking to 3600 MHz by Kingston. See comments, I can live with that, no issues after several months of stability. However, really confusing and annoying!!

WD Gold drive

With so many drives out there, it is hard to choose. As explained, this drive is used for running rsnapshot. The previous drive did its job for a relative short time but simply became to small. So it was time to go from 8 TB to 16 TB. We have quite a few WD Gold drives in the field and so far, no problems at all. This is the product sheet.

However, I was asking myself if it might be reasonable to just do the daily back-up and than power down in between. Well, people running servers will always advice against this – never stop a running disk drive. To a certain extent I agree, experience shows drives running for a decade and refusing duty after one stop and start. But modern drives? So I asked WD support.

You shouldn’t be worried, especially on such low usage case scenario. Of course, we cannot know for sure as there might be many factors that influence the life spam of a drive, read and write cycles, correct power supply, environment etc.. but if everything is under normal conditions, WD Gold drives are designed for a lot of usage.

So it seems save to say a once a day on and off cycle wouldn’t harm.

But then again, why take the trouble? Rule of thumb: Every 1 Watt costs 2€ per year. So 5 years 5 W is 50€. Hardly an argument considering the price of the disk is a tenfold.

Some additional notes: The drive is fast indeed, from NVM to SDA I clocked speeds exceeding 200 MB/s by far. On top of that, it is not a noisy drive.

Status

A working solution… but homeless!

More later!

A simple test on the command line… Write or paste the yellow stuff and try to understand.

This comprehensive page is a practical collection about CAD faces with layman explanations of mathematics and additional code fragments. It deals with vectors, angles, normals, 2D projections, rotations and more. The best news is that even BricsCAD Classic supports both Lisp and 3D commands like RuleSurf. Even with limited resources you can build great solutions.

I made FlatMesh in an attempt to create blanks from ruled surfaces. While the basics are relative easy – translating 3D coordinates to 2D – it turned out that the exceptions are the real math challenge. I couldn’t find a this page like this, in order to clarify and understand the subject. So this page was born. I hope it is of help. If you think something is wrong, missing or can be done better, just drop a comment.

Definitions

• Mesh: A mesh is a collection of faces. A mesh forms a surface object. Often, representation in CAD is like a collection of rectangles. The use of rectangles has the advantage of clarity. On the other hand, in 3D, the four corners of each rectangle are almost never in one plane. To fix that, each rectangle consists of two adjacent triangles called faces. The common side of these two faces forms an invisible diagonal of a visible rectangle – the remaining sides of the two triangles.

• Face: See Mesh. A face is by definition a flat polygon and almost always a triangle in a CAD environment. A face has three edges and vertices. Complex surfaces can be simulated by using triangular faces. Faces with four vertices are not suitable for complex surfaces.
• Vector: A vector is a direction with a magnitude.
  • A vector V is represented as
  • with a direction
  • and a length or magnitude
• Dot product: An algebraic operation on two vectors and with angle in between, resulting in a scalar (number, not a vector) of the area of the parallelogram of and , written as
  . More…
• Cross product: An algebraic operation on two vectors and with angle in between, resulting in a vector perpendicular to both and , written as
  . The magnitude of the resulting vector equals the area of the parallelogram of and . Note that the area – part of both dot and cross product – is valuable for solving equations. is positive when using the right hand rule. More…
• Normal: A line, ray or vector perpendicular to something. In this case we mean a vector perpendicular to a plane. The side of the plane on which the normal starts is determined by the right hand rule. Therefore the order of and is important, and . More…

Math solutions

Calculate the magnitude of a vector

For vector with value , the magnitude or length is according to the Pythagorean theorem.

For vector with and , the length is

.

Calculate the unit vector of a vector

A unit vector of a vector has the same direction but has a length or magnitude of 1. It can be retrieved by dividing each x, y and z of a vector by the magnitude of that vector, resulting in a new vector.

Calculate the angle between two vectors

In 2D, it is easy to comprehend. 3D is harder. For example grep a pencil in each hand and position and point them randomly before you. What on earth is the angle? Now bring the origins together. At that point, you can imagine a plane through the three points and it becomes clear there is an angle. Then the question becomes: What is the angle? And: Do you want the angle from pencil A to pencil B or the other way around? Finally, you can look at the plane from to sides, which changes the answers too. So there is enough complexity.

Using arccosine

The angle between and …

Example

AB = 1,2,3
AC = 4,5,6
|AB| = SQRT(1^2+2^2+3^2) = 3.74
|AC| = SQRT(4^2+5^2+6^2) = 8.77
AB.AC = 1*4+2*5+3*6 = 32
acos((AB.AC)/(|AB|*|AC|)) = acos(32/(3.74*8.77)) = 0.226 rad = 12.9 degrees

Here, the angle range is 0 to . Although technically correct, that may not always be what you want.

Using arctangent

The same angle again…

Is a vector angle obtuse, perpendicular or acute?

Continuing with the previous… Instead of, or in addition to, calculating an angle, the dot product is enough to say whether the angle is obtuse, perpendicular or acute. It is depending on the sign of . More specific:

• If m is positive, the angle is acute.
• If m is zero, the angle is right, perpendicular.
• If m is negative, the angle is obtuse.

A rectangle contains two adjacent faces. We can say something about the angle between the faces by first calculating the normal vectors of each face.

Calculate the normal of a face

The normal vector is the cross product of vector AB times vector AC. According to the right hand rule, it is written as

Example

AB = (1,2,3)
AC = (4,5,6)
AB????AC = (2*6-3*5,1*6-3*4,1*5-2*4) = (-3,6,-3)

The opposite normal vector is AC????AB, being AB????AC with opposite signs, i.e. (3,-6,3).

The magnitude of normal AB????AC is area . So you can tell something about angle CAB if you have the magnitudes of all three vectors.

Calculate 2D projection of a face – Pythagorean

With three coordinates A, B and C known of a 3D face, we can calculate a projection in 2D. Alternative, law of cosines can be used here too.

Calculating C based on A is (0,0) and B is (p,0)

Summary

Known:
Distances p, q, r
Constraints:
Point A = (0,0)
Point B = (p,0)
Point C is above axis AB
First Cy is positive
z coordinates always 0
Requested:
Coordinates of C.
Answer:
C = ((p^2+r^2-q^2)/(2*p),sqrt(r^2-t^2))
Subsequent Cy values can be negative too, i.e. -sqrt(r^2-t^2)

Rationale

A: (x,y,z)
C: (x',y',z')

Variant 1  Variant 2 ( is OR)
 CAB <= pi()/2  CAB > pi()/2 =>
x <= x'  x > x'

r^2 = t^2+s^2 =>
s^2 = r^2-t^2

q^2 = (p-t)^2+s^2  (p+t)^2+s^2
= (p-t)^2+r^2-t^2  (p+t)^2+r^2-t^2
= p^2-2pt+t^2+r^2-t^2  p^2+2pt+t^2+r^2-t^2
= p^2-2pt+r^2  p^2+2pt+r^2 =>
2pt = p^2+r^2-q^2  -p^2-r^2+q^2 =>
t = (p^2+r^2-q^2)/(2*p)  (p^2+r^2-q^2)/(-2*p)
s^2=r^2-t^2
s=sqrt(r^2-t^2)  s=-sqrt(r^2-t^2)

With two answers for t it is tempting to just code both values. Annoying and itching is the fact I cannot say anything beforehand about CAB.

Hmm, is that so? Climbing from the bottom – the resulting formula’s – up, there is fragment p^2+r^2-q^2. Wait, Pythagoras! That should be 0 when CAB is 90 !

More specific:

One problem solved, one problem created! Let’s see, If p^2+r^2-q^2 < 0then t = (p^2+r^2-q^2)/(-2*p) and else t = (p^2+r^2-q^2)/(2*p). So t is always a positive value and whether it is on the left or right side of x=0 (point A) depends on the value of p^2+r^2-q^2.

More specific, as an x-coordinate, t = (p^2+r^2-q^2)/(2*p). And that is always true! Great, and even my old brains survived this.

A final note about s. It is a square root so the argument can be both positive and negative. It won’t bother us for the assumed first C, but it will bother us for subsequent C’s and all D’s.

Calculate 2D projection of an adjacent face

Getting the coordinate D is similar to finding C.

One segment of the RuleSurf result is build out of two triangles or faces. Using FlatMesh means in most cases: Start with A and B and calculate C and D, then treat those resulting C and D as a new set of A and B and start allover, until the complete mesh is processed. In most cases, the first picture is in play. However, sometimes the second picture can be in play. In addition, even C can be under axis AB but focus is on D for proper explanation.

A,B,C and D are 3D points. There is a plane ABC. D is somewhere relative to this plane. We need to know where D lies. More specific, in a planar view to ABC, is D under or above axis BC? To get a better impression, look at it from a different angle:

This question seems not easy to answer, but, as long as we talk about angles, we can say that:

• If the angle between the face normals is acute, D lies above BC.
• If the angle between the face normals is obtuse, D lies under BC.

After calculating the normals as explained before, the dot product is all we need to answer the question. Just remember to use the right hand rule.

That was actually the hard part. D is more or less calculated the same way as C.

However, we need to use the axis CB (not AB) as the base, as the mirror line for when D gets under CB. Finally, C and B were rotated around A, D should also be rotated properly. That is where starts to play a role. Rotating…

Calculate rotation of a coordinate in 2D

Seriously written for mathematicians, so don’t read https://en.wikipedia.org/wiki/Rotation_(mathematics). Pff… Okay, it boils down to this:

Given is coordinate pair x,y and angle α. Get x',y' by using:

x'=x*cos(α)-y*sin(α)
y'=y*cos(α)+x*sin(α)

In order not to get unexpected results, angle α is positive when counter-clockwise – in this example it is a positive value.

Translations of coordinates

This one is easy, translations like command Move is just adding static values to x, y and z values.

Programming solutions

The purpose of this code is educational. It works and aims to show the structure. Unless you experience slow processing, it should be sufficient.

Lisp lacking Arcsine and Arccosine in AutoCAD

This code can be used for (acos ...):

1

(defun acos (r / ) (atan (sqrt (- 1 (expt r 2))) r))

This code can be used for (asin ...):

1

(defun asin (r / ) (atan r (sqrt (- 1 (expt r 2)))))

BricsCAD uses the native Lisp function. Tip: Ditch AutoCAD for Lisp programming, BricsCAD CAD-Lisp is way faster and is constantly under development with for example not a two decades old IDE, search “Blade BricsCAD”.

Distance between point a and b

In Lisp there is a function (distance a b) but it is tempting to use your own function because (distance a b) treats all points 2D when it encounters one 2D point. An alternative function (dist3d a b) works always 3D and calculates “the square root of the sum of the squares of the delta x, y and z values”. It could be as simple as this one-liner :

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9

(defun dist3d (a b / )
   (sqrt
      (+
         (expt (- (car b) (car a)) 2)
         (expt (- (cadr b) (cadr a)) 2)
         (expt (- (caddr b) (caddr a)) 2)
      )
   )
)

With the distance between a and b, a is x,y,z and b is x',y',z', the formula in spreadsheet notation is:
dist3d=sqrt(((x'-x)^2)+((y'-y)^2)+((z'-z)^2))

Vector between point a and b

For a vector coordinate set from a to b, subtract coordinates of a from b. In Lisp:

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(defun vector (a b / )
   (list
      (- (car b) (car a))
      (- (cadr b) (cadr a))
      (- (caddr b) (caddr a))
   )
)

Cross product of vector a and b

Take care of the order of a and b, it affects the sign of the coordinates. In Lisp:

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2
3
4
5
6
7

(defun cross-product (a b / )
   (list
      (- (* (cadr a) (caddr b)) (* (cadr b) (caddr a)))
      (- (* (car a) (caddr b)) (* (car b) (caddr a)))
      (- (* (car a) (cadr b)) (* (car b) (cadr a)))
   )
)

Dot product of vector a and b

In Lisp:

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3
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5
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(defun dot-product (a b / )
   (+
      (* (car a) (car b))
      (* (cadr a) (cadr b))
      (* (caddr a) (caddr b))
   )
)

Magnitude of vector a

In Lisp:

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9

(defun magnitude (a / )
   (sqrt
      (+
         (expt (car a))
         (expt (cadr a))
         (expt (caddr a))
      )
   )
)

Unit vector of vector a

In Lisp:

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(defun unit-vector (a / l)
   (setq l (magnitude a)
   (list
      (/ (car a) l)
      (/ (cadr a) l)
      (/ (caddr a) l)
   )
)

Return value: A list containing the x, y and z values of the unit vector.

Acute angle between vector a and b

In Lisp, is an angle acute or obtuse? This code treats right angles as acute which makes the function very fast but not always suitable, check first.

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2
3

(defun acute (a b / )
   (if (>= (dot-product a b) 0.0) T)
)

Return values: If the angle is right or acute, T (True) is returned. the dot product is zero or positive, T (True) is returned. If the angle is obtuse, nil is returned.

Vector angle between a and b (acos)

In Lisp, see angle between vectors based on acos.

Return value: Angle in radians.

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2
3

(defun vector-ang (a b / )
   (acos (/ (dot-product a b) (* (magnitude a) (magnitude b))))
)

Rotation of point a over angle g

In Lisp. Angle g in radians, sign is positive when counter clock wise. Point a: only x and y are evaluated.

Return value: A list containing the calculated x and y values after rotation.

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(defun rot-pt (a g / sg cg x y)
   (setq sg (sin g) cg (cos g) x (car a) y (cadr a))
   (list
      (- (* x cg) (* y sg))
      (+ (* y cg) (* x sg))
   )
)

Deze pagina biedt oplossingen en achtergrondinformatie over het maken van uitslagen of, meer specifiek, het afvlakken van een regeloppervlak – een “ruled surface”. Er zijn nogal wat toepassingen. Denk bijvoorbeeld aan uitslagen van een spiraalboor voor grondboren, hout- of metaalbeplating in de scheepsbouw en gebogen wanden en plafonds in de architectuur. Het doel is om een ​​krachtig hulpmiddel te krijgen, zodat je aan de slag kunt met BricsCAD (en waarschijnlijk AutoCAD – niet getest).

Deze oplossing kan alleen worden gebruikt op regeloppervlakken. Het is als: Als je een model met papier kunt buigen – en je kunt heel creatieve dingen met papier doen – dan verdient dit onderwerp je aandacht. Het is verrassend wat je kunt doen.

Zie verder:

This page provides solutions and background information on making blanks or, more specific, flattening a ruled surface. There are quite a few applications. Consider, for example, blanks of a spiral drill for ground drilling, wood or metal plating in shipbuilding and curved walls and ceilings in architecture. The objective is to get a powerful tool so you can get started with BricsCAD (and probably AutoCAD – not tested).

In my humble opinion, the subject is totally undervalued. Time to change that!

Warning! The current code does not yet contain a solution for apparent intersecting faces, see “caveats”. So be careful and always check results.

This solution can only be used on ruled surfaces. It is like: If you can bend a model with paper – and you can do very creative things with paper – then this subject deserves your attention. It is surprising what you can do.

The subject deals with a lot and the structure is like stray notes – sorry for that. Therefore: Use the table of contents to navigate.

Feel free to leave a comment!

The gallery or “Is it free?”

FlatMesh is free to use for you. Free doesn’t exist? That is right. If you use the code, send some photos of blanks, semi-finished or finished products. Others – and that includes me – learn from it. Is that a good deal?

Global information

Introduction

Chronic itches… Through the years it was a wish to come up with something like this but… Time is almost never my friend! Do you recognize that? While coding a project recently, I thought: “Hey, this is close to that almost forgotten project” and so I started this page.

It turned out to be a bit harder than expected. For details, see the accompanying post “Applied Mathematics concerning CAD Faces” – all you ever wanted to know about faces.

If you look at the pictures on this page, you’ll understand why it is interesting. Feel free to use the code and have fun with it. If you think you can improve something, you’re more than welcome, leave a comment.

Is this surface developable or not?

First: What is a developable surface? I am Dutch and would rather say de- or un-wrapable, “afwikkelbaar” (Dutch) but math people talk about “ontwikkelbaar” (Dutch). Translated, it boils down to unwinding, unrolling, unwrapping. Germans say “Abwickelbare Fläche”. The answer is as can be inspected: See https://en.wiktionary.org/wiki/d%C3%A9velopper explaining “veloper” means “wrapping”. Now you know also where “envelope” comes from and what it means.

Long story short: If you can make it from sheet, without stretching and only bending, such as paper or metal sheet, it is developable. Why should it all be so hard?

A cone illustrates this very well:

The ruled surface

Considering the above cone: Can you imagine you take a piece of clay and than move a ruler over two guides? One guide curve is the bottom circle, the other one a miniscule nano circle on the top.

That principle is applicable to whatever guide curves you choose. So let’s have another example:

Impressive? I thought so, a complex shape made from a sheet of whatever.

But: Not all ruled surfaces are developable surfaces, not all developable surfaces can be made in one piece. For example:

In this case the blank will intersect with itself – that is why there are often welds visible on these kind of spiral drills.

Last, not least, neutral lines

Probably obvious but important: What you construct with this toolset are basically neutral lines, or better, neutral planes.

The neutral plane of a real blank is the imaginary plane that does not shrink or extend when bending the blank. From the inside of a bending, it typically lies between 30 to 50% of the material thickness (K-factor).

Switching bending direction also switches the location of the neutral plane. Quick and dirty assuming it is always 50% is attractive in many cases – if tolerances tolerate it. In that case you have to offset the mesh 0.5*thickness to both sides. Stated more practically, just make sure your two open guide curves are positioned properly before applying a RuleSurf command.

CAD commands

• Making a ruled surface mesh can be done with command RuleSurf. You select two guide objects like splines and next a mesh is created as if a ruler is equally moved over the guide curves.
  • Make sure you set 'Surftab1 to a proper value. This value is the amount of faces.
  • Curves may not be closed.
  • That implies there is always a (straight) start side and end side of the blank.
  • When selecting the guides, take care to select the corresponding beginning sides of the guides.
• Next thing: Is it a proper mesh? Internally it should be a polyline (yes, really, with flag 64 set, forget that). How to retrieve that information? Properties should state “Polygon Mesh” with “M vertex count” equal to 2.
• That leaves the Lisp-command FlatMesh…

How FlatMesh works

In short

Issue the FlatMesh command and select a proper mesh. That is it. You’ll get a flat blank.

Background information

You already have a fair idea of how it works. The Lisp code extracts the 3D coordinates of each vertex. Those coordinate lists are converted into an ordered coordinate list for each guide or rail, two in total. All we can determine is the distance between successive 3D-coordinates. With that information, the coordinates are flattened to 2D.

Therefore, the mathematics around a triangle with known sides is important. The Lisp code contains a loop that translates the coordinates into new ordered coordinate lists and rebuilds the mesh coordinates, but with z = 0 and flat triangles. Easier said than done but, in hindsight, not too difficult either.

Caveats

• It is a lot of calculation to get a blank and sub results are cumulative, so error margins are cumulative too.
  • Use your logical sense, like: “Is this result reasonable?”, like always in life.
• About the amount of faces in a mesh:
  • Use SurfTab1 to set the amount.
  • Too few faces in the mesh will result in an undersized blank without smooth boundaries.
  • Too many faces in the mesh will impact the amount of calculation errors.
  • Experiment with different values of SurfTab1 and project the resulting blanks over each other.
  • You’ll notice, for example, that the cone on this page has a very reasonable quality with 100 faces.
• If guides contain sharp edges, you should check the blank at those corresponding points. For editing, explode the polyline, zoom in deep enough, do a fillet command with radius 0 and use join to create the polyline again.
• Beware of intersecting faces – both 2D and 3D. This version of FlatMesh does not take this into account and blanks will contain errors.

Qualitative mathematics

For details, see the accompanying post “Applied Mathematics concerning CAD Faces“

Algorithms

The only challenge is the used algorithm. A 3D-face (green) of a ruled surface is made out of a set of two triangles – or the blue or the magenta variant. Triangles are needed because the corner points of a 3D-face (almost) never lay in a common plane.

How about rule of cosine?

When two points of a triangle are known, just like the distances between all three points, several algorithms can be used, see below.

The challenge is to reduce the error margin. For example, using rule of cosine for a triangle that has one very short and two very long sides – which is almost always the case – introduces a small error. With a Surftab1 value of 100, this error is magnified. That is why testing FlatMesh and getting things right is more work than the actual programming.

Although the rule of cosine is tempting because it is easier than what is below, the drawbacks should keep us from using it in this case – I’ve learned the hard way.

What is the alternate algorithm?

Here are two blue meshes, representing the flat blank of two red curves – all 2D:

The used algorithm is based on the Pythagorean theorem for calculating C and D with A and B given. It is easy to calculate distances between 3D-points and those distances are all we need (and all we have) to do the job.

The left mesh is a special case with A and B similar, we’ll skip that one for now and focus on the right example.

These are the possible varieties:

Discussion about calculation of D is skipped because it is similar to calculating C. That leaves us with the left two variants. Don’t worry, I did put the coding for D in the program 😉

UCS command

One could also use a style where switching from object UCS to world UCS is applied in a loop. It is really quick and dirty – for example, you don’t want (command …) functions in your code. However, it could work.

Quantitative mathematics

For details, see the accompanying post “Applied Mathematics concerning CAD Faces“

The steps

• Calculating C is step one – based on A is (0,0) and B is (p,0).
• Then there is D. Is D under or above AB?
• However A and B are not horizontal aligned. Therefore the rotation of C relative to A is calculated, based on angle AB.
• As a last step, a translation is needed because A is not (0,0).
• This procedure is a loop for every next point set where not only D, but also C can change from under or above axis AB. Enough complexity I think.

Get the code

Read this first

Understand the caveats, see TOC.

Understand how to use it, see TOC.

There always may be circumstances where the results are not what you expected. FlatMesh is not a polished and fool-proof product. That does not make it less valuable.

However, if you want added functionality, I can always give you a quote.

Feel free to leave a comment if you find a bug.

The code contains several possible algorithm implementations. At the bottom of the code you can switch between them. However, I would suggest you keep it as is.

For readability and educational value, the code is not optimized for speed. Though Lisp is interpreted, it is low level, close to processor instruction sets. Therefore, I expect it to be processed in a blink of an eye.

Downloads

Bugs Feature requests

• With common start point of guides the first point set is not calculated correctly. > Solved.
• In cases with sharp creases in the 3D model, guide that are at some points perpendicular, expect trouble. If a guide is smooth and the blank contains sudden changes of direction, you probably hit this situation.

Als je niet geïnteresseerd bent in de details, kan je hier de GHS-labels downloaden. De labels zijn omgezet van EPS naar SVG en kunnen daarom direct op webpagina’s of anders worden gebruikt.

https://www.unece.org/trans/danger/publi/ghs/pictograms.html bevat de afbeeldingen.

Dit is het bestand met alle variaties.

Als DXF gewenst is, kunnen Inkscape SVG-bestanden eenvoudig worden opgeslagen als DXF-bestanden.
Het gebruikte script:

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#!/bin/sh
# put this file in the directory with eps files and run it
for thefilename in *.eps
do
	file=$(basename "$thefilename")
	ext="${file##*.}"
	filename="${file%.*}"
	inkscape  $file --export-plain-svg=$filename'.svg'
done

De pictogrammen

Deze pictogrammen zijn SVG-formaat. Je kunt de afbeeldingen direct downloaden of de link gebruiken om ze allemaal tegelijk te krijgen.

If you are not interested in the details, you can download the GHS labels here. The labels have been converted from EPS to SVG and can therefore be used directly on web pages or different.

https://www.unece.org/trans/danger/publi/ghs/pictograms.html contains the images.

This is the file with all variations.

If DXF is desired, Inkscape SVG files can easily be saved as DXF files.
The script used:

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#!/bin/sh
# put this file in the directory with eps files and run it
for thefilename in *.eps
do
	file=$(basename "$thefilename")
	ext="${file##*.}"
	filename="${file%.*}"
	inkscape  $file --export-plain-svg=$filename'.svg'
done

The pictograms

These pictograms are SVG format. You can directly download the images or use the link to get them all at once.

There are plenty of ways to create configuration files. They all have pros and cons. What are the possibilities for CAD-Lisp?

Choosing a configuration file syntax

Win.ini is nice because of its simple structure. The downside is that it is limited, lacking array functionality for example. On the other side of the spectrum there is XML. Way to complex for simple tasks.

How about JSON?

For CAD-Lisp I often used Unix style configuration, and doing arrays in semicolon format. Nowadays JSON is popular and that looks a bit like structured lists. The example on https://en.wikipedia.org/wiki/JSON:

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{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 27,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "office",
      "number": "646 555-4567"
    },
    {
      "type": "mobile",
      "number": "123 456-7890"
    }
  ],
  "children": [],
  "spouse": null
}

Or simply… Lisp!

Nobody can deny the similarities found in Lisp. So it is very tempting to go back to basic Lisp format, simply because it supports all that Lisp supports, because, well, now we get to the core, it is Lisp in itself!

This is how the file looks, translated to Lisp format:

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(
   (firstName "John")
   (lastName "Smith")
   (isAlive T)
   (age 27)
   (address
      (
         (streetAddress "21 2nd Street")
         (city "New York")
         (state "NY")
         (postalCode "10021-3100")
      )
   )
   (phoneNumbers
      (
         (
            (type "home")
            (number "212 555-1234")
         )
         (
            (type "office")
            (number "646 555-4567")
         )
         (
            (type "mobile")
            (number "123 456-7890")
         )
      )
   (children ())
   (spouse nil)
)

Just like with JSON, the structure and nesting is immediately clear. Pros: simplest syntax. Cons: bracket matching is the only separation (that is a pro too). A real problem arises when reading the file, (read-line ...) checks for matching brackets and the first line will result in a “malformed list” error.

However, making sure all brackets match per line means also that (read-line …) directly applies data type list and not data type string.

And that can be consolidated to, for example, only main level entries without loosing information:

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   (firstName "John")
   (lastName "Smith")
   (isAlive T)
   (age 27)
   (address ((streetAddress "21 2nd Street")(city "New York")(state "NY")(postalCode "10021-3100")))
   (phoneNumbers (((type "home")(number "212 555-1234"))((type "office")(number "646 555-4567"))((type "mobile")(number "123 456-7890")))
   (children ())
   (spouse nil)

Needless to say, a proper parenthesis aware editor, such as Notepad++ and Geany are of great help here.

Suppose this file is saved as “cfg2bb-test.cfg” in the search path, it is used below. But first, as a one liner, the configuration becomes this:

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((firstName "John")(lastName "Smith")(isAlive T)(age 27)(address ((streetAddress "21 2nd Street")(city "New York")(state "NY")(postalCode "10021-3100")))(phoneNumbers (((type "home")(number "212 555-1234"))((type "office")(number "646 555-4567"))((type "mobile")(number "123 456-7890")))(children ())(spouse nil))

Parsing it

Let’s create some code:

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; (c) NedCAD 2020
; cfg2bb parses a list config file to blackboard variable "bb<cfg".
; syntax: (load "cfg2bb")(cfg2bb "cfg-uri")(setq cfg2bb nil)
 
(defun cfg2bb ( cfg-uri / cfg-file cfg-obj file-line list-line list-result)
 
; Error handler
  (defun *error* (msg)
    (princ "error: ")
    (princ msg)
    (princ)
  )
 
; Getting default settings
  (if (setq cfg-file (findfile cfg-uri))
    (progn
      (princ (strcat "\nParsing " cfg-file ". "))
      (setq cfg-obj (open cfg-file "r"))
      (while (setq file-line (read-line cfg-obj))
        (setq list-line (read file-line))
        (setq list-result (append list-result (list list-line)))
      )
      (close cfg-obj)
      (vl-bb-set 'bb<cfg list-result)
      (princ "\n") (princ (vl-bb-ref 'bb<cfg))
    )
    (princ (strcat "\nError: Can't find " cfg-uri ". Check existence and or support file search paths. "))
  )
  (princ)
)

What happens if we do:

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(load "cfg2bb")

and then:

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(cfg2bb "cfg2bb-test.cfg")

Output will be a list:

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Parsing C:\Users\nanos\AppData\Roaming\NedCAD\Config\cfg2bb-test.cfg. 
((FIRSTNAME John) (LASTNAME Smith) (ISALIVE T) (AGE 27) (ADDRESSES (STREETADDRESS 21 2nd Street) (CITY New York) (STATE NY) (POSTALCODE 10021-3100)) (PHONENUMBERS ((TYPE home) (NUMBER 212 555-1234)) ((TYPE office) (NUMBER 646 555-4567)) ((TYPE mobile) (NUMBER 123 456-7890))) (CHILDREN NIL) (SPOUSE NIL))

So if we wanted the phone numbers, we could do:

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(nth 5 (vl-bb-ref 'bb<cfg))

Resulting in the list:

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(PHONENUMBERS ((TYPE "home") (NUMBER "212 555-1234")) ((TYPE "office") (NUMBER "646 555-4567")) ((TYPE "mobile") (NUMBER "123 456-7890")))

Tips

• In order to parse the file only once per CAD session, the value is written to the blackboard, or better, assign the blackboard variable to a blackboard variable for your application. Then, when opening a drawing, check if the blackboard variable exists, if not, parse the configuration, else, propagate the existing blackboard variable.

From time to time we need a laptop for CAD. A cost effective solution is the Lenovo Ideapad L340-15API with standard 16GB RAM plus a Ryzen 7 GPU. Here is the story and the findings. Only modification is an upgraded M2 unit.

We’re totally impressed by performance, combined with a desktop screen. The laptop screen itself is not the very best but okay when on the move. The AMD Ryzen 7 performance is absolutely impressive. That, combined with its low price, leaves room for only one conclusion: Highly Recommended!

Upgrading the NVM

Need more!

256GB is definite not enough when working with virtual machines. The upgrade is an Intel SSD 660p, 1 TB. I try to avoid “SSD” and call it “NVM”: Non Volatile Memory, rather not Solid State Disk. Solid State Device is a not preferred alternative.

Spoiler alert: Where is the 256 GB NVM?

Okay, this is funny, the original 256 GB NVM is simply not there! Then what is? A good old fashioned 2.5″ SSD! And that is good news for an expanding future.

Considerations

Pre-installed Windows is not needed so it is tempting to simply install Xubuntu and go. But I want a way back. On the other hand, for the time being I really don’t need Windows. Playing around with a SystemRescueCd and dd, there is always a way to deal with this in the future. Setting up Grub and things are back to production level. Interim solution: Boot order in UEFI.

Opening the case

Simply remove all screws from the back cover and use a credit card to pry it all open. Take it easy and you won’t damage anything.

Place it all and close it up

Needed: A M2 screw that is not included (M.2, is that a coincidence?). Luckily I always have threaded rods and nuts, so I made it myself, seriously, see the picture, hammered top.

The “BIOS”

Keep the power button pressed for reboot, hit F2 several times, go to the “boot” tab, change order by selecting with cursors and using F5 and F6 to change order:

1: Put the new M.2 NVM on top.
2: Boot stick with Xubuntu
3: Stuff on SSD
…

In case you want an extra Linux install later, same procedure but put USB with the image on top then.

Save and reboot (F10) for installing Linux.

All the next steps…

See the start of BricsCAD Linux pages. That will keep you busy for now 😉 But… There are some specific things too:

Lid solution

I hate laptops because of their small working area, phones even more. Luckily I can connect a 40″ 4k screen. But closing the laptop lid turns off the big screen too. How to solve that?

sudo su
nano /etc/systemd/logind.conf

Put the next line at the bottom in logind.conf:

HandleLidSwitch=ignore

ctrl-s and ctrl-x, saving and closing, and then:

service systemd-logind restart

Xubuntu is a bit juggling with screen layouts, do Whisker menu > Settings > Display and drag your laptop screen to the right, make the big display primary. Now you have your menu on the big screen. Don’t mirror he screens when the big screen resolution is different.

Printing in Linux is very different, but not harder. In fact, scripting creates extra possibilities…

THIS ARTICLE IS UNDER CONSTRUCTION. YOUR POSITIVE INPUT IS APPRECIATED.

All related parts: 1: Introduction 2: Linux base install 3: More user software 4: Tuning Linux 5: Tuning your software 6: Getting BricsCAD working 7: Publishing your drawings

PDF as the base

History

PostScript, in .ps files, is a page describing language. You copy the file to a PostScript printer and you’re done. That is how it started early 80th, the printer did the processing.

PDF is a descendant of PostScript, lacking typical program language features, adding the possibility of embedded fonts and interactive media. Development: ~2000. For more: see Wikipedia.

PDF’s are processed in the computer itself and printed to all kinds of printers, contrary to PostScript. Raster Image Processing, RIP, is what is done to turn a PDF to a raw stream of print pixels.

There are printers that can deal directly with PDF by the way.

Linux and macOS are much more centred around PostScript and PDF printing than Windows. Centralizing PDF in the printing process is obvious, contrary to Windows printing.

Pitfalls

PDF is never a substitution for a CAD file. As “page printing oriented”, it lacks precision and it has never been intended to be an exchange format. People sending PDF’s for use in CAD systems should think twice and consider sending proper CAD files.

Unintended scaling is a pitfall that needs you attention, in particular when using Windows. If you want proper scaling, check your process carefully.

CUPS for printing

CUPS

CUPS (Common UNIX Printing System) lets a computer act as a print server, a host, for printers connected to that computer, using USB or network.

A user, a client, on the same computer or a different one, sends a print job to a CUPS host. CUPS does ripping, spooling and everything needed to get a result from the target printer.

Printer dialogues for setting up printers in modern Linux distro’s typically configure CUPS invisibly. You can find the “real” interface at http://localhost:631/printers/.

Command line: using lpr or lp

In BASH, command lpr or lp stands for line printing. It uses CUPS. lpr and lp are not the same thing, they more or less do the same thing.

On the CUPS site lives a clearly written document about using lpr and lp. You should read it, what follows here is a summary of tools to get jobs done.

Getting all information

What printers do I have?

Example, issue command lpstat -t in a terminal (ctrl-alt-t):

$ lpstat -t
scheduler is running
system default destination: EPSON_ET_4750_Series
device for Epson-Stylus-Pro-11880: socket://10.105.2.159:9100
...
printer Xprinter-XP-360B is idle.  enabled since zo 18 aug 2019 15:19:10 CEST

Two possibilities for example for printing on the command line:

lp -d EPSON_ET_4750_Series drawing.pdf
lpr -P Epson-Stylus-Pro-11880 drawing.pdf

What options does a specific printer have?

Issue command lpoptions -p printername -l to l(ist) options in a terminal:

$ lpoptions -p EPSON_ET_4750_Series -l
PageSize/Media Size: Letter 4x6 5x7 8x10 101.6x180.6mm *A4 A5 A6 Legal B5 B6 3.5x5 Postcard Env10 EnvC6 EnvDL 5x8 FanFoldGermanLegal 195x270mm 215x345mm
MediaType/Media Type: *Stationery PhotographicHighGloss Photographic PhotographicSemiGloss PhotographicGlossy PhotographicMatte StationeryLetterhead Envelope
ColorModel/Output Mode: *RGB Gray
Duplex/Duplex: None *DuplexNoTumble DuplexTumble
cupsPrintQuality/cupsPrintQuality: Draft *Normal High

Syntax:

Tag1/Tag2: Option1 *Option2 Option3 ...

*values are defaults. Before starting to combine all this…

The real party starts when using large format printers – not unusual in a CAD environment. Again:

$ lpoptions -p Epson-Stylus-Pro-11880 -l
InkSet/Cartridge Option: *MatteBlack
MediaType/Media Type: VELVET_FINE_ART_PAPER_MK WATERCOLOR_PAPER_RADIANT_WHITE_MK TEXTURED_FINE_ART_PAPER_MK ULTRASMOOTH_FINE_ART_PAPER_MK CANVAS_MK DOUBLEWEIGHT_MATTE_PAPER_MK ENHANCED_MATTE_PAPER_MK ARCHIVAL_MATTE_PAPER_MK PLAIN_PAPER_MK *ENHANCED_MATTE_POSTER_BOARD_MK
Color/Color: *Color ABWP
PrintQuality/Print Quality: Draft Speed Quality *Max_Quality
HighSpeed/High Speed: *Off On
Mode/Mode: ChartsAndGraphs *Standard AdobeRGB
InputSlot/Source: *RollPaper RollPaper_Banner Sheet
PageSize/Size: *Custom.WIDTHxHEIGHT A4 A3 A3+ A2 A1 A1+ A0 A0+ Letter USB USC USD USE ARCHA ARCHB ARCHC ARCHD ARCHE B5 B4 B3 B2 B1 B1L B0 B0+ 8x10in 10x12in 11x14in 12x12in 16x20in 24x30in 30x40in 36x44in 50x64in 60x75in 64x80in 30x40cm 40x60cm 60x90cm
Borderless/Borderless: *Off On
AutoCut/Auto Cut: *Off SingleCut DoubleCut NormalCut
Density/Color Density: 50 55 60 65 70 75 80 85 90 95 *100 105 110 115 120 125 130 135 140 145 150
DryingTimePerPrintHeadPass/Drying Time per Print Head Pass: *0 5 10 15 20 25 30 35 40 45 50
PaperFeedAdjustment/Paper Feed Adjustment: 0 5 10 15 20 25 30 35 40 45 50 55 60 65 *70 75 80 85 90 95 100 105 110 115 120 125 130 135 140
PaperSuction/Paper Suction: *Standard 1 2 3 4
PlatenGap/Platen Gap: *Auto Wider Wide Standard Narrow

With a lot of power comes a lot of options, that was fun! And finally I understand what my printers are really able to do, information so hard to find in manuals and sales info.

What other options do we have?

Continue reading this. For example:

lp -o landscape drawing.pdf

… is an option.

Putting it all together

Based on the example before, we could do:

lp -d Epson-Stylus-Pro-11880 -o media=Custom.1059x1500mm drawing.pdf

… for a 1500mm print from a 42 inch roll.

And the configuration possibilities seem endless, and when all options (-o abc -o def -o …) are defined properly, the process is under control. No surprises any more when printing and that is the power of CUPS for macOS and Linux versus Windows printing. But wait…

And… The finishing touch!

With knowledge about Unix/Linux printing it becomes tempting to automate things. There are two things to consider:

• Look for Creating Saved Options, for creating “instances” of your printer with exactly the right settings – mostly paper sizes.
• Consider using BASH scripts for hassle free printing. Example:
  $ ./drop_A0_pdf_on_me.sh

Hope you liked it so far, by writing I learned a lot myself too! Now, where were we… BricsCAD and Printing!

BricsCAD and Printing

That was a long introduction with details on PDF and CUPS. What it means for BricsCAD: Forget about PC3 files, it all boils down to creating proper PDF’s.

Considerations

• All printing is centred around Print as PDF.pc3
• Consider filing your print PDF’s for later reproduction purposes.
• Do CPAGESETUP: Print as PDF.pc3 is greyed out, there are no other printers.

Setting up media sizes

CPAGESETUP results in this:

At this point something is odd:

• If you do ctrl-p > Preview, you get a proper PDF.
• If you do ctrl-p > <Enter>, you get an A0 proposition and a custom size, made with button 2, is not in the list any more.
• That problem does not occur when doing a -plot command. So -plot is a workaround, just as saving the Preview.
• It is temporary, it has the attention of developers (2019-08-30)

Additional Notes

This information screams for further automation…

How to get a Lisp list of CUPS printers?

By piping things I could transform $ lpstat output to an impressive but Q&D one liner that generates the requested list, paste this in a terminal:

echo ")" | (lpstat -p | sed 's/printer /(\"/' | cut -d ' ' -f 1 | sed 's/$/\")/' && cat) | (echo "(\"cups_printers\"" && cat) | tr '\n' ' '

This results in a list, which can be processed in Lisp:

("cups_printers" ("Epson-Stylus-Pro-11880") ("EPSON_ET_4750_Series") ("Xprinter-XP-360B") )

How to get the paper size of a layout?

Retrieving the paper size of a layout in Lisp, more paste, not working yet (2019-08-31), looks like:

(vla-get-canonicalmedianame (vla-item (vla-get-layouts (vla-get-activedocument (vlax-get-acad-object))) (getvar 'ctab)))

This, combined with a table that links pc3 media sizes to CUPS media sizes and some Lisp and BASH programming might be the inspiring thought for anyone of creating a cupsplot command 🙂

Next…

Continue with part 8: Maybe later…

Optimizing your Linux CAD environment. A proper work space means increased speed and optimized working pleasure…

THIS ARTICLE IS UNDER CONSTRUCTION. YOUR POSITIVE INPUT IS APPRECIATED.

All related parts: 1: Introduction 2: Linux base install 3: More user software 4: Tuning Linux 5: Tuning your software 6: Getting BricsCAD working 7: Publishing your drawings

GUI

Position taskbar

I think Microsoft did a good job putting it down. Every movement of your head up is a burden on your neck vertebrae. So you may consider and act:

RMB Panel > Panel Prefs > unlock
LMB move (on handle, edge)
RMB Panel > Panel Prefs > lock

Status notifier

The status bar, the most right panel with indicators…

RMB > Panel > Add New Items > Action Buttons, Keyboard Layouts, Screenshot, Show Desktop, Workspace Switcher > Add button > ...

Ordering icons: RMB > Move

Keyboard layouts

Now that you have a panel entry for keyboard layouts, configuration is needed. This depends on where you live. I have an “English (US)” layout and want to add an “English US international with dead keys” layout. For switching I want to use the keys left-ctrl+left-shift.

Menu > Settings > Keyboard > Tab Layout > [] Use system defaults > Add, "English (US, int., with dead keys)" > OK > Change layout option: Left Ctrl + Left Shift > Compose key: Right Win > Close

Tick tock

Optionally change time area Clock:

RMB > Properties: format field > %A, %d-%m-%Y, %T

Font DPI settings

Menu > Settings > Appearance > Tab Fonts > DPI

Have some windows open and play with settings. For example, my 40″ 4k screen is set to 130 dpi. BricsCAD deals reasonably good with it.

Theming

Really? Okay, just a bit then, before we discuss things like “ugly”.

Active window themes

A coloured window title bar shows what window has focus. Out of the box, only “Daloa”, “Kokodi” and “Moheli” offer that. See:

Menu > Settings > Window Manager > Tab Style

Appearance

In general, lots of settings are scattered but can be found under Whisker > Settings. For example, dpi is one but you may want to increase font sizes too – a tab under Appearance. Play around… If you want less fancy, more functionality, contrast:

Menu > Settings > Appearance > Tab Style > Adwaita (dark?)

Icons… Very personal but functionality is important too. For example, I work often with LibreOffice master documents and “Humanity” has different icons for .odm files.

Menu > Settings > Appearance > Tab Icons > Humanity

Networking

SMB Linux client example

• Everything as root.
• Install:
  apt install cifs-utils
• Obtain the IP number of the server with the name of the share.
  For example, 10.105.1.1/sharename, sharename is “projects” in this example.
• Create a local directory /data/servername/sharename, for example
  mkdir -p /data/projects
• Change the rights of sharename to 2770 and owner and group to username. For example
  cd /data/
  then
  chown JanJansen:JanJansen projects/
  then
  chmod 2770 projects/
• Add the following line to /etc/fstab:
  nano /etc/fstab
  Then, add this line at bottom:
  //10.105.1.1/projects /data/projects cifs uid = 1000,gid = 1000,credentials=/etc/samba/user,noexec 0 0
  then ctrl-s and ctrl-x.
  • Using systemd, this link contains this, which may be interesting for laptop use, travellers:
    //host/share /net/share cifs noauto,nofail,x-systemd.automount,x-systemd.requires=network-online.target,x-systemd.device-timeout=10,workgroup=workgroup,credentials=/foo/credentials 0 0
• Put data in file /etc/samba/user:
  nano /etc/samba/user
  add this
  username=JanJansen
password=yap@ssword
  then ctrl-s and ctrl-x.

NFS

Where Samba is based on SMB technology, reverse engineered Windows server stuff, NFS is for Unix networks.

If you don’t need SMB, go for NFS. There are times we go “off grid”. Packed with a data copy we work in a far away country without internet and our (NedCAD) workstations utilize only NFS where one Linux workstation exports the data copy to other Linux clients. Back home, we rsync everything to the main server.

Interesting for military and all other kinds of off grid operations too, but that is outside the scope of this post. If you want to implement it, read for example this post.

More…

Screensavers, power management

In 19.10 it became a bit confusing. However, it seems safe to state that if you apply settings in “Screensaver”, it overrules the rest of the other – possibly conflicting – settings. So start with the first item below:

Menu > Settings > Screensaver > ...
Menu > Settings > Session and Startup > ...
Menu > Settings > Power Manager > ...

But… This does not always work (20.04) and using your search engine gives tons of often useless results. So read on about xset and LightDM…

Xset

Command xset is a user preference utility for X-Windows. An overview of current settings can be retrieved with: xset q. So xset s off -dpms turns the screen saver function off and disables Energy Star DPMS features. See man xset for more…

LightDM

LightDM is the display manager… LightDM starts the X servers, user sessions and greeter (login screen).

What kind of problems can be solved here? Quoted from the TOC:

• Disabling Guest Login
• Hiding the User List
• Allow Manual Login
• Setting an Automatic Login
• Changing the Default Session
• Changing the Greeter
• Adding System Hooks
• Changing the Wallpaper
• Help, I can’t see my Desktop!

More information can be found on the Ubuntu LightDM page.

Dual monitor support

Running into trouble with dual monitor configs, example with two Full HD monitors? Create an executable .sh shell script file, you can add a link to it in “Session and Startup” and or create a launcher (RMB panel). It can contain something like this, tune to your needs, don’t just copy:

#!/bin/sh
xrandr  --output VGA-0 --mode 1920x1080 --pos 1920x0 --rotate normal --output  DVI-0 --off --output HDMI-0 --mode 1920x1080 --pos 0x0 --rotate normal 

These kind of scripts come in handy when you change monitor layouts often, laptop with additional monitor and beamer for example.

Next…

Continue with part 5: Tuning your software

So you have a running system with almost all software installed, out of the box. But there is more: This page… With a huge amount of additions.

THIS ARTICLE IS UNDER CONSTRUCTION. YOUR POSITIVE INPUT IS APPRECIATED.

All related parts: 1: Introduction 2: Linux base install 3: More user software 4: Tuning Linux 5: Tuning your software 6: Getting BricsCAD working 7: Publishing your drawings

Preparing for software installation

As preparation, a list of packages that are handy and not in the standard installation follows, “apt install” (as root) is the command for this.

Do not simply install everything, just take what you need.

• You can copy the table and paste (ctrl-v) it in LibreOffice Calc, cell A1.
  • Now you have all data in columns A, B, C and D
• Next, remove direct formatting of cells:
  • ctrl-a
  • ctrl-m.
• In Mousepad, you can paste contents of column A
• Suppose you want to install package5, package13, package20 and package45.
• Create a text line as followed:
  • apt install package5 package13 package20 package45
• Copy this line to the clipboard
• Open a terminal ctrl-alt-t
  • Enter “sudo su” with password when asked. You have root privileges (#).
  • Paste the apt install … text line on the command line. Installation should start.

Choose your tools

• If you don’t need it, don’t install it. Make sure you know what you are installing
• You can sort the table by clicking once or twice on the headers.
• The links are for helping you decide…

Additional remarks

• Check the output of your terminal carefully for errors.
• Fonts that are compatible with Microsoft fonts in terms of geometry:
  • fonts-croscore for
    • Times New Roman (Tinos)
    • Arial (Arimo) and
    • Courier (Cousine)
  • fonts-crosextra-carlito for Calibri and
  • fonts-crosextra-caladea for Cambria.

Snap

Some packages are better used as snap packages. Please check first if there is an install in synaptec in order not to install twice. If a package is already installed you’ve got two valid packages and you should or could remove one. For example, youtube-dl is a dependency of smplayer. So snap install youtube-dl is okay, but the next step could be apt remove youtube-dl. On the other hand, you may want to keep both. Command which youtube-dl should tell you where the program is located.

• https://snapcraft.io/youtube-dl
  sudo snap install youtube-dl
  Rationale: Older versions often don’t download media properly.
  UPDATE: Parasitic organization RIAA wasn’t so pleased with sharing our culture, so an alternative approach is added below. No comments including “PaRIAA” or “DiarRIAA”, now is the time to laugh and for the rest it sucks.
• https://snapcraft.io/blender
  sudo snap install blender --channel=2.79/stable --classic
  Rationale: If you have older blend files, they behave as intended in this latest period before the 2.80 revolution.
  

AppImage

Download, change rights to executable and run. That is the principle of an AppImage, that contains all needed to run. I tend to keep them in my home directory and make shortcuts to the Whisker by using menu editor.

• Olive is a very promising video editor and brand new. See https://olivevideoeditor.org/download.php.

/usr/local/bin

This is the dedicated place on your system to store your own program collection. Normally it is attractive to put them somewhere in your home directories, but system wide you have to be here. So youtube-dl is an example of it:

• youtube-dl:
  sudo curl -L https://yt-dl.org/downloads/latest/youtube-dl -o /usr/local/bin/youtube-dl
sudo chmod a+rx /usr/local/bin/youtube-dl
  Updating: youtube-dl -U
  Usage: youtube-dl <URL>

PPA’s

Personal Package Archives. Not discussed here in detail. If you run into trouble with a checked and secure package from the official distributions, and there are ppa’s, you can consider using them. But you also effectively give access to the ppa maintainer – a security issue.

Some packages are bleeding edge. They are added in the table but you may want to use alternatives for now (2020 Okt.):

• Currently no entries 😉
  

Next…

Continue with part 4: Tuning Linux

So Xubuntu it is. Ready to install?

2020-10-25: An installation of 20.10 did fail, resulting in a proper install of 20.04, see https://vanderworp.org/en/amd-pro-4650g-workhorse/ for details…

THIS ARTICLE IS ALWAYS UNDER CONSTRUCTION. YOUR POSITIVE INPUT IS APPRECIATED.

All related parts: 1: Introduction 2: Linux base install 3: More user software 4: Tuning Linux 5: Tuning your software 6: Getting BricsCAD working 7: Publishing your drawings

Preparation

You need partitions, free disk space. Assumed is an empty, new system. In case of existing operating systems, consider a back-up before creating a place for Linux and installing it.

Download

LTS or not

I tend to install the “latest and greatest”. However, I often run into serious trouble with hot versions. So, resisting the temptation, it is smart to choose a LTS (Long Term Support) version. Xubuntu 20.04 to be precisely. In 2022 I’ll update probably to version 22.04. Before that is done, images are made of the working installation.

Where to get all files?

Download an iso file from https://xubuntu.org/download.

• Create the installation CD or stick
  • Linux: “Startup Disk Creator” -> to USB
  • See https://help.ubuntu.com/community/Installation/FromUSBStick for more.

Installation

• Start up and usually call F12 / F11 / F2 / del for a BIOS startup menu when starting a computer. Some old computers have difficulty installing from USB, then bake a DVD first.
• Current Linux distro’s expect UEFI, so there is no reason to disable it. For older distro’s, UEFI can be annoying, dive into the BIOS and make sure you can start without UEFI. General: installation is straightforward, follow all instructions and everything is (usually) good. It is to consider arranging some things differently …
• About asking installing proprietary drivers… Try not to, in most cases it is okay.
• About partitioning a drive, use GPT as partition table. This eliminates all kind of discussions about primary, extended and logical partitions. And keeping things simple, for a workstation that is reinstalled after a limited number of years, is obvious. What partitions do we need?
  • First a new GPT partition table
  • Then we need an ESP, an EFI System Partition. Reserve for example 1 or 2 GB’s for this it will always be enough.
  • One ext4 partition with mount-point “/”
  • A swap partition (the kernel likes it) that is, for example, the half or whole amount of RAM.
• Just follow the installation steps and you can’t go wrong.
• Also do all updates when finished.

Next…

Continue with part 3: More user software

Linux is about choice, freedom and security. Great news but it looks hard to deploy a professional CAD environment in Linux. BricsCAD is the key to it and these pages are to help unlock it, from A to Z.

THIS ARTICLE IS UNDER CONSTRUCTION. YOUR POSITIVE INPUT IS APPRECIATED.

All related parts: 1: Introduction 2: Linux base install 3: More user software 4: Tuning Linux 5: Tuning your software 6: Getting BricsCAD working 7: Publishing your drawings

CAD and Linux were difficult to combine until a few years ago. Ironically, because many CAD systems have started on Unix. But that aside.

There are a few great freedom based basic CAD programs for small projects. But for serious and professional work, there was actually nothing. Bricsys has changed that with a closed source application BricsCAD. For an overview of CAD programs, look at this.

Why these pages?

Why invent the wheel? With so many possibilities for software and configuration in Linux, many things can go wrong. You’ll notice it takes long to troubleshoot errors or just find out how to configure things.

These pages are based on a working solution.

Even that is no guarantee things will be the same, different hardware can cause different problems for example. But, I think it might help a lot of people to get familiar with a great experience, instead of getting frustrated. And remember, there are tons of information on the net, use it. And a lot of people willing to help within the community.

Another thing, splitting all in dedicated pages results in more possibilities, not using Xubuntu but Debian plus XFCE keeps other pages valuable for example.

Why you should not use BricsCAD in a Linux environment

Windows releases have focus of Bricsys. Linux and macOS lag behind. You’ll probably hit more bugs with Linux, just like performance, 3D graphics will probably be a bit slower, 2D is okay.

I think it is fair to speak that out loud. You should ask yourself the question whether all pluses and minuses justify a decision to walk a Linux plus BricsCAD road. If you have a Linux system, it is a good idea to download a 30 day trial.

Having said that, it should be mentioned that Bricsys support is outstanding, problems are solved very fast. Besides that, the more users on the Linux plus BricsCAD road, the smaller the differences become between OS specific variants.

Personally, I think I made a good choice following this road and I hope you’ll join me! If that is the case, you’ll find these pages more than valuable.

What is used?

Hardware

$ cat /proc/cpuinfo
...
AMD A10-7870K Radeon R7, 12 Compute Cores 4C+8G
...

So an AMD APU is used. That covers the graphics and computing and is a safe and cost effective solution. AsRock motherboard by the way, recommended because of their support.

Operating system

A workstation based on Xubuntu … Level: A little familiar with Linux is desirable but otherwise, your search engine is your friend. This page should be a good start.

What is Xubuntu? It is Ubuntu Linux with an Xfce Desktop Environment “look&feel”, being basic, without bloat, perfect for a production environment.

Many Ubuntu flavours have already been tried. All these flavours have their pros and cons, but net, Xubuntu is the most appealing, it is simple like Windows 7 classic, XP and still offers many possibilities by installing packages of other Linux flavours.

Tailoring a system requires effort. For many people, Ubuntu is standard, out of the box – just like macOS and Windows – also good enough. For power users, the following pages can be inspiring. Don’t expect eye candy on Xubuntu.

BricCAD running on the newest Linux versions is not a good idea. That is why we always try to lag behind with versions. It is also very tempting to go for Debian with XFCE, but for now we stick to Xubuntu.

Things to remember

terminal: In a terminal you enter commands. Search in your menu or try ctrl-alt-t.

sudo: Sudo ensures that you can perform tasks as installations as “root” (admin). If you read: sudo command_x, remember that you can also permanently work as root by first typing “sudo su“, back to the user: “exit“. If it says “# command“, do it as root and if it says “$ command“, do it as a user.

RMB is short for Right Mouse Button. And there are LMB and MMB and even 2LMB and 2MMB.

Next…

Continue with part 2: Linux base install

BricsCAD runs on Windows, macOS and… Linux. Hello security, privacy and independency! There are also some caveats and this post deals with them.

THIS ARTICLE IS UNDER CONSTRUCTION. YOUR POSITIVE INPUT IS APPRECIATED.

All related parts: 1: Introduction 2: Linux base install 3: More user software 4: Tuning Linux 5: Tuning your software 6: Getting BricsCAD working 7: Publishing your drawings

Installation

Installing is just as straight forward as other versions: Download from bricsys.com, run the .deb file, start the program and choose trial or enter your license code.

Tuning

Actually, everything seems to run reasonably fine. I installed CuLite, it makes things easier. I like to link to this older post, maybe some things are useful here: https://forum.bricsys.com/discussion/30468/amd-gpu-some-reccomended-settings-when-running-bricscad/p1.

Next…

Continue with part 7: Publishing your drawings

THIS ARTICLE IS UNDER CONSTRUCTION. YOUR POSITIVE INPUT IS APPRECIATED.

All related parts: 1: Introduction 2: Linux base install 3: More user software 4: Tuning Linux 5: Tuning your software 6: Getting BricsCAD working 7: Publishing your drawings

LibreOffice

Sometimes LibreOffice (LO) tries to be too smart. If you type MHz, you don’t want Mhz but there are plenty examples with multiple capitals you want to keep. Automatic placement of capitals as first character is annoying in Calc. Here we go…

• Languages
  • Use synaptic to search for “hunspell”, select languages for installation (like hunspell-xx) and apply.
  • LO: Menu > Tools > Options > Language Settings > Languages > Default …
  • Activated after restarting LO
• In Writer > bottom screen > LMB “language X” > more
• Menu > Tools > AutoCorrect options:
  • Tab Options: Everything turned off. Maybe you like “URL Recognition”.
  • Tab Localized Options: Everything turned off, quotes too.
  • Be aware it is set per language, more languages means setting it again.

Firefox

This web browser deserves tuning. Privacy is an issue these days. See for example this article with links to extensions. Other functions can be added too so it’s time for add-ons, extensions.

Installing your old environment is possible too. For example, export and import your “Logins & Passwords” and bookmarks. Missing an import button? Search the net, it will probably get fixed in time.

Then there is the weird ctrl-tab and ctrl-shift-tab behavior – “it is not a bug, it is a feature”. See this article for a not working solution, so we’re stuck with the ctrl+page-up and ctrl+page-down alternative, yes you need long fingers if you can’t use your right ctrl and yes, people have never visited the moon and yes, this is an awesome improvement like walking backwards home or upside down or whatever. Moz://a… THINK!!

First paste about:config and be careful 🙂 Then… When you alt+lmb, you want to “save as”. Enter browser.altClickSave in the Search space. 2lmb on tag browser.altClickSave and see the value change from false to true. Hmm, looks broken. Again: Moz://a… THINK!!

So let’s continue with working wonderful things!

Paste about:addons as address for your local settings, take some time to browse for Firefox Add-ons…

• Cookie AutoDelete: Quote… “Control your cookies! This WebExtension is inspired by Self Destructing Cookies. When a tab closes, any cookies not being used are automatically deleted. Whitelist the ones you trust while deleting the rest. Support for Container Tabs.”
• DuckDuckGo Privacy Essentials: Quote… “Privacy, simplified. Our add-on provides the privacy essentials you need to seamlessly take control of your personal information, no matter where the internet takes you: tracker blocking, smarter encryption, DuckDuckGo private search, and more.” It changes your default search engine. I think this is not bad because Duckduckgo respects your privacy. If you want to change setting, paste about:preferences#search as address.
• uBlock Origin: Quote… “An efficient blocker: easy on memory and CPU footprint, and yet can load and enforce thousands more filters than other popular blockers out there.”
• Privacy Badger: Privacy Badger automatically learns to block invisible trackers.
• Languages: In synaptic, search for “firefox-locale” and choose your additional language packs. If your language is okay, don’t install.
• Dictionaries: Choose your languages and install…

Next…

Continue with part 6: Getting BricsCAD working

Part 0: Drawing mathematical functions in BricsCAD and AutoCAD. Calculating x and y values with a spreadsheet and drawing the curve in BricsCAD (and AutoCAD, ZWCAD). Post-processing: smoothing and exporting as SVG for LibreOffice, PDF.

This is a series about creating mathematical curves in BricsCAD (and AutoCAD).
Part 0, just hackish with a spreadsheet, result driven.
Part 1, the math, understanding ways to iterate.
Part 2, the coding, techniques available.

Mathematical curves in BricsCAD and AutoCAD. This part shows how you can do this in a simple way.

With LibreOffice Calc, Inkscape and Notepad++ you have the tools, free software. The rest is a matter of doing. The following is an example, lots of viewing and learning pleasure!

https://www.youtube.com/watch?v=46t4YBz_mEM

This is a series about creating mathematical curves in BricsCAD (and AutoCAD).
Part 0, just hackish with a spreadsheet, result driven.
Part 1, the math, understanding ways to iterate.
Part 2, the coding, techniques available.

THIS ARTICLE IS UNDER CONSTRUCTION. YOUR POSITIVE INPUT IS APPRECIATED.

In part 1 the mathematics are explained. It turns out to be a solid base with a very functional algorithm in order to draw approximated curves.

Status Quo

This pages offers clues for coding. I’ve tried several concepts as described in part 1. After ending up writing a few hundred lines of code I decided to stop because a proper solution is simply a lot of work in unpaid time that lacks.

That is not the complete story, after tinkering, I also came to the conclusion that using a non uniform rational basis spline, or NURBS , or spline is a proper alternative after all and, combined with the theories in part 1, it offers best possibilities (and consumes a lot of my time).

Does it mean that this page is worthless? No, it offers additional insights that you will not find on the net in a structured way.

Making a NURBS

Ways in Lisp

In Lisp there are several ways to create a NURBS or spline:

• Very easy with (command “._spline” …), not recommended for production environments.
• The object-way with (vla-AddSpline …), not discussed further.
• The old fashioned way, using (entmake …), discussed here.

Example

“Entmake” that spline

Consider the following code:

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(setq point-list '((0 0) (1 1) (2 0) (3 -2) (4 0)))
(entmake
   (append
      (list
         '(0 . "SPLINE")
         '(100 . "AcDbEntity")
         '(100 . "AcDbSpline")
         '(70 . 4)
         '(71 . 3)
         (cons 74 (length point-list))
      )
      (mapcar '(lambda (xy) (cons 11 xy)) point-list)
   )
)

The first line is paste-able on the CAD command line as:

(setq point-list '( (0 0) (1 1) (2 0) (3 -2) (4 0)))

The second part as:

(entmake (append (list '(0 . "SPLINE") '(100 . "AcDbEntity") '(100 . "AcDbSpline") '(70 . 4) '(71 . 3) (cons 74 (length point-list))) (mapcar '(lambda (xy) (cons 11 xy)) point-list)))

Going through the code:

• “70 . 4” is DXF code 70 for spline type 4, i.e. “Rational spline”.
• “71 . 3” means degree 3.
• There are 5 points, so: “74 . 5”.
• “(mapcar “(lambda (xy) (cons 11 xy)) point-list)” returns a list with code “11” sublists: “((11 0 0) (11 1 1) (11 2 0) (11 3 -2) (11 4 0))”

That is all it takes to create a spline. Code “11” points are fit-points, going through the curve, what we want. This could also be “10” for control-points.

There is much more to be aware of, see DXF-codes for Splines. and more on NURBS at Wikipedia.

How to feed mathematical functions to the program?

We’ll start with a few examples.

Function files

Let’s say, we have a function . What we do is put it in a file with extension fun, for example: curve.fun. The filename should represent what you define in the file.

Please, do yourself a favour, use a suitable text editor like notepad++ and mark your code as Lisp during editing.

Syntax explained

What is in the file? First of all: Valid Lisp code, more on that later. What is needed is:

• A safety factor to make sure the curve is within the deviation limits: fuzzy
• A maximum deviation: dev
• A tolerance as a part of dev: tol
• A start value for x: xmin
• An end value for x: xmax
• Divide calculations: xdiv
• The function: fx

A valid file contains:

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(tol 0.2)
(fuzzy 0.000)
(dev 0.05)
(xmin 0)
(xmax 2)
(xdiv 1)
(fx (* x x))

That should be clear, setq assigns a value to a variable. What can go wrong? The number of opening parenthesis should be equal to the number of closing parenthesis. That is the number 1 error.

Defining your functions

Arithmetic functions

Here is a list of some arithmetic functions…

Examples

• Note that 6 is an integer and 6.0 is a real.
  • 
  • (!)
• Angles are in radians, 2*pi radians is 360 degrees.
• Expressions are evaluated inside out: (than-this (first-this))

The line containing a function, (fx (* x x)), is a list in a list. The examples below are like (fx (example)).

• (* x x)
• (expt x 2)
• (+ (* x x) (* 6.0 x) -2.5)
• (- (sin x) (* x (cos x)))
• (abs x)
• (int x)
• (sqrt (expt x 2))

How configuration data is handled

What curve does is very basic: It reads lines from the files an interpretes them when they are in list format. A bit more in detail: the line “(xmax 3.2)” is a string. By using the read function, the line is converted to a list. From that point, further processing in Lisp is possible with a set statement (not setq).

Additional considerations

The math part describes a way to calculate valid fit points by iterating checks based on core CAD-Lisp functions. In addition, it is possible to use a set of curve measurement Lisp functions – link broken, cache:

In BricsCAD these functions are also available on OS-X and Linux.

Internally, LibreOffice Writer has been used for technical documentation for many years:

• Writer is very strong in combination with style sheets and
• SVG format is perfectly supported. Vector-based images can therefore be inserted very well.

When you work with large documents, there are two annoying peculiarities you should be aware of.

• The first is that the program stops organizing pages when the document becomes large. This can be overcome in an ugly way. Just add more trees, by always embedding images as a character. It concerns this bug. If you deal with this the right way, then Writer has no problem with documents containing hundreds of pages.
  
• The other one is that it is not possible to link templates to documents. This sounds a bit crazy and yes, it may be considered to be a bug.

An extension “Template Changer” was available for linking template files. However, it does not work with new versions. That is why we created a BASH script as a tool to solve this. It has been tested on Linux but should also work with Cygwin on Windows. OS-X should work with minor changes, like the date function in Unix does not require an @ sign.

The underlying idea is that you have documentation projects where both the documents and the templates are in the same directory. If that is the case with you, then this script can help you.

You can paste the following to a text file called “cht.sh”, give it executable rights, put it in your documentation directory,  and start attaching templates to your documents.

Hope you like it!

Update 2018-11-19: Now both ODT and ODM files are supported.

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#!/bin/bash
 
# Template CHanger alternative
# This script uses xmlstarlet, zip and unzip.
echo
echo ./cht.sh, CHange Template...
echo This script inserts or replaces, a template XML node in a 
echo LibreOffice Writer file, by modifying meta.xml and adding an
echo absolute url for template location. It accepts both
echo document and master document files and template files.
echo xmlstarlet is expected to be installed.
echo This is for documentation projects where Writer files and Templates
echo reside in the same directory!
echo USE AT YOUR OWN RISK, HAVE A BACK-UP READY, wiebe-nedcad-nl
echo Run script always in directory with documents, cd your_project
echo "Usage: cht <OTT-file> <ODT-or-ODM-file>"
echo Example: ./cht.sh template.ott writer.odt
echo
 
## Variables I, more below Checks
 
# General
TEMPL=$1
DOC=$2
WORKDIR="temp_extracted"
 
## Checks
 
# Do files exist with right extension?
 
if [ -f $TEMPL ] && [ "${TEMPL: -4}" == ".ott" ]; then
   echo "File $TEMPL found."
else
   echo "ERROR: Writer template $TEMPL does not exist or is not valid. Aborting."
   exit 1
fi
 
if [ -f $DOC ] && ([ "${DOC: -4}" == ".odt" ] || [ "${DOC: -4}" == ".odm" ]); then
   echo "File $DOC found."
else
   echo "ERROR: Writer document $DOC does not exist or is not valid. Aborting."
   exit 1
fi
 
# Do we have xmlstarlet?
 
hash xmlstarlet 2>/dev/null || { echo >&2 "ERROR: xmlstarlet is required. Please install this first. Aborting."; exit 1; }
 
## Variables II
 
# XML node "meta:template" values
echo Node meta:template will contain the following bare attributes:
# xlink:type xlink:actuate xlink:title xlink:href meta:date
 
# Static
N_XLINK_TYPE="xlink:type" && V_XLINK_TYPE="simple"
echo $N_XLINK_TYPE -- $V_XLINK_TYPE
 
# Static
N_XLINK_ACTUATE="xlink:actuate" && V_XLINK_ACTUATE="onRequest"
echo $N_XLINK_ACTUATE -- $V_XLINK_ACTUATE
 
# Template name
N_XLINK_TITLE="xlink:title"
NO_EXT="${TEMPL%.*}"
V_XLINK_TITLE=${NO_EXT##*/}
echo $N_XLINK_TITLE -- $V_XLINK_TITLE
 
# Absolute template location
N_XLINK_HREF="xlink:href"
V_XLINK_HREF="$PWD/$TEMPL"
echo $N_XLINK_HREF -- $V_XLINK_HREF
 
# Template time
N_META_DATE="meta:date"
# Lower epoch time sec to force updating document styles
BELLE_EPOCH_COR=-1
BELLE_EPOCH_X=$(stat -c %Y $TEMPL)
BELLE_EPOCH=$((BELLE_EPOCH_X+BELLE_EPOCH_COR))
V_META_DATE=$(date -d @$BELLE_EPOCH +%Y-%m-%dT%T.%9N)
echo $N_META_DATE -- $V_META_DATE
echo
 
## The proces
 
# Unzip the document file
 
mkdir -p $WORKDIR
if [ -z "$(ls -A ./$WORKDIR)" ]; then
   echo "Ready for processing meta.xml"
else
   echo "ERROR: ./$WORKDIR is not empty and may contain an unzipped document file. Aborting."
   exit 1
fi
unzip -q $DOC -d $WORKDIR
cd $WORKDIR
 
# If exists, delete node meta:template, add node and subnodes via pipes
xmlstarlet ed -d "/office:document-meta/office:meta/meta:template" meta.xml | \
xmlstarlet ed -s  "/office:document-meta/office:meta" -t elem -n meta:template | \
xmlstarlet ed -i  "/office:document-meta/office:meta/meta:template" -t attr -n $N_XLINK_TYPE -v $V_XLINK_TYPE | \
xmlstarlet ed -i  "/office:document-meta/office:meta/meta:template" -t attr -n $N_XLINK_ACTUATE -v $V_XLINK_ACTUATE | \
xmlstarlet ed -i  "/office:document-meta/office:meta/meta:template" -t attr -n $N_XLINK_TITLE -v $V_XLINK_TITLE | \
xmlstarlet ed -i  "/office:document-meta/office:meta/meta:template" -t attr -n $N_XLINK_HREF -v $V_XLINK_HREF | \
xmlstarlet ed -i  "/office:document-meta/office:meta/meta:template" -t attr -n $N_META_DATE -v $V_META_DATE \
> temp.xml && mv temp.xml meta.xml
 
# What is the result?
echo meta.xml is now: && echo
cat meta.xml && echo
 
# Back-up original file
mv ../$DOC "../${DOC%.*}.bak"
echo A .bak file is created && echo
 
# Create modified Writer file, mimetype first
zip -rq ../$DOC mimetype .
 
# Cleaning up
cd ..
rm -rf $WORKDIR
echo Finished && echo