Re: [brlcad-devel] GSoC 2014 Voxelize

[Aditi B. <adi...@gm...>]

Hello Daniel !


 > I had been testing voxelize for quite a while now but the command hangs
> the
> > software to the state that it has to be reopened again. It is not
> > functional. I have gone through the code , still trying to understand it.
>
> Can you provide an example?  Used geometry, voxelize parameters?  This
> behavior could be caused by using a too small voxel size (conversion
> needs a long time).
>
If I give voxelize command prior to ray tracing, no error is displayed
rather software hangs. Voxelize hangs unpredictably at times on just
passing voxelize newreg.r oldreg.r command, without explicitly defining
anything else. Reasons yet unknown, right now trying out on other systems
too. Too small voxel size would lead to delay, agreed but when I am
defining nothing explicitly, I think the same reason should not be  the
cause.



> You can find the core of the algorithm in /src/libanalyze/voxels.c.
> The creation of the voxels will be done via the create_boxes callback
> function.  There are two such functions already implemented: One in
> src/libged/voxelize.c which creates RPPs (the mged command) and
> another in src/conv/g-voxel.c which writes the coordinates to a file.
>

Going through that.


>  > As a part of my project I would like to implement this functionality
> > properly.
> > Along with voxel generation, I would like to add features that
> voxelization
> > would help rendering to BRL CAD many useful abilities.
> >
> > My idea is to extend voxelize library incorporating in it , following
> > features:
> > 1. Functions to change the color, texture, material and size of voxel
> etc.
> > 2. If two objects collide, following the laws of motion in ideal space,
> what
> > would be the resultant shape, this would be done firstly by voxelizing
> the
> > two objects then evaluating the shift in individual voxels according to
> the
> > laws of motion and redrawing the finally distorted image by
> de-voxelizing.
>
> Maybe you could think more about creating new call-back functions for
> special purposes and how to integrate them in BRL-CAD.
>

I think of may be multi-threaded voxelizing, to improve the efficiency.
What would you suggest as some special purposes call back functions?


>
> > 3.This would also need the de-voxelize function.
>
> This is another topic, similar to getting the lines and surfaces from a
> pixmap.
>
> Yes, indeed.
http://fab.cba.mit.edu/classes/S62.12/docs/Lorensen_marching_cubes.pdf ,
would this not help us to get there?

I really wish to get started with some patches, could you please suggest me
some relevant patches that could clarify my understanding of the code and I
could contribute to BRLCAD in some concrete way.

Regards,
Aditi Bhatnagar