In article <3a635d70@news.povray.org>, Ken Cecka 
<cec### [at] alumniwashingtonedu> wrote:

> Have you thought much about how you would handle CSG?  I don't know 
> anything about Warp's tesselation patch that Chris referred to, but 
> CSG can be a show-stopper.  Finding an algorithm to generate meshes 
> for arbitrary CSG combinations is difficult.  Usually you end up with 
> a tradeoff between speed and accuracy. 

Warp's code uses the marching tetrahedrons algorithm and can handle any 
arbitrary shape, including CSG. There is a speed/accuracy/memory 
tradeoff...and the meshes aren't as optimized as they could if you made 
them yourself, but it works, and OpenGL would just be a preview, so you 
wouldn't even need very high quality meshes.


> For a static OpenGL display, the algorithm doesn't need to be 
> particularly fast since you only calculate the mesh once, and then 
> are free to explore your scene with a mobile camera (fun!).

I'm not clear on whether he is working on that kind of interactive 
display or simply using OpenGL for extremely fast preview images.

 
> If you want animation, you need to be able to quickly recalculate CSG 
> meshes (consider a scene with a difference of two spheres, where one 
> of the spheres slides from left to right during the animation).

Or just compute all the images and play back the results. Or just do 
things the way POV does them now, only using OpenGL to do the rendering 
instead of the raytracing engine.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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