SuperCAD library PovRAY export

monkstone

SuperCAD library PovRAY export

in Contributed Library Questions • 2 years ago

I have recently been experimenting with the superCAD library, and had some success. However I think I have detected at least one error in the hard coded povray export template.

RedT = texture{ pigment{color rgbf<1,0.5,0.1,0.5>} // corrected code
not = texture{ pigment{color rgbf<1,0.5,0.0.1,0.5>}

This is a simple typing error, unfortunately I'm a real beginner with povray and even after correcting this error the renderer continues to complain of multiple 'no pigment type given', which seems to go back to the definition of Brun, used to define BeigeLwD?

I get 'no pigment type given', error at all lines that include texture{BeigeLwD}.

Nevertheless congratulations are due to Guillaume on all his efforts. The export to *.obj seems to work well. I managed to import the *.obj it into blender, but I'm even less competent with the blender interface.

I am tempted to try to code my own template based on the one exported by StructureSynth, which seems to be much simpler.

Replies(5)

monkstone

Re: SuperCAD library PovRAY export

2 years ago

I've done some further experimenting with the superCAD library, with yet more surprising but kind of interesting results. The result should have been a simple menger (or probably a half of a menger, bisected by the ground plane). This weird result seems to be caused by Guillaumes fuzzer kludge which produces a random error. As far as I can tell povray 3.7 beta (the latest I can get for linux) does not require this kludge.

I was very suspicious when I found that wavefront obj export worked so well.

monkstone

Re: SuperCAD library PovRAY export

2 years ago

Well I'm on a roll here replying to my own question. However I thought it worth reporting that there is a bias introduced by Guillaumes fuzzer kludge (only positive increments), so if the kludge is really needed I suggest the following modification.

//Avoid colinear points from p5
//POVRAY COMPLAIN ABOUT THIS
double fuzzer = 0;
private double fuzz(){
fuzzer += (Math.random() - 0.5)*0.001d;
return fuzzer;}

Subtract 0.5 as above to remove the positive bias introduced by the kludge ( which of course shows up worse with sketches like my menger sponge).

davbol

Re: SuperCAD library PovRAY export

2 years ago

i've never used superCAD, but i've exported a LOT of pov sdl from p5 and can assure you that there is NO need to add random "fuzz" to valid triangle vertex coordinates in order to get them to work with pov.

the only triangles pov will complain about are those where all three vertices are colinear (and/or coincident) -- that is, they don't actually form a valid triangle. you can get these from careless use of triangle strips/fans/etc, or from just blatantly degenerate geometry like a rectangle with zero width and/or height, etc.

if you add "fuzz" at random you actually introduce the possibility of turning a small valid triangle into a degenerate one! (though granted that chance is exceedingly small) so rather than do that, here are several approaches you might try:

- alter your code to not produce degenerate triangles in the first place

- alter superCAD to check for degenerate triangles and not export the entire triangle

- do nothing, just ignore the warnings from pov, and it simply won't render those degenerate triangles

monkstone

Re: Re: SuperCAD library PovRAY export

2 years ago

I think the answer is to get rid of the kludge altogether ie just ignore the povray warnings. Which are essentially just warning you the triangle is not going to get drawn (or is it rendered transparently?), but it is not my call, superCad belongs to Guillaume LaBelle. However I was quite interested in the images produced by the dodgy kludge, multiple small errors can produce some interesting effects........

monkstone

Re: Re: SuperCAD library PovRAY export

2 years ago

davbols comments on another topic (concerning DXF export) has inspired me to sort out another issue with supercad povray export. Mainly there is povray coordinate issue with supercad export.

The problem is exactly the same as the DXF export, out of the screen is negative 'Z' with povray and conventionally 'Y' is up (if you ask me processing is odd in this respect). Result is my test 'T' is now the right way up.

Update 21 December:-

I have now devised an "F" test which tests left to right orientation, and produced a simple correction for the original superCAD library follow the "F" test link.

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