Christopher James Huff wrote:
> 
> Some time ago, I heard about another method that follows rays through 
> the scene one path at a time instead of splitting the rays at each 
> surface. When a surface that both reflects and refracts is hit, one of 
> the two is chosen at random.

That's how you do it with path tracing - noisy images are usually the 
result unless you use really lot of samples.

> I did some tests using my own raytracer, and it is possible to get good 
> results with a very good increase in rendering speed. I've come up with 
> two different algorithms based on this technique. The first chooses 
> randomly between refraction and reflection for each material evaluation, 
> which gives grainy results unless a lot of samples are used. The second 
> makes these choices for an entire pass of the image. That is, it renders 
> the image in multiple passes, deciding whether to do reflection or 
> refraction for each trace level and using the same choices for the 
> entire image pass. 64 passes with this technique took 5 minutes, where 
> the traditional technique required 9 minutes.

You mean 64 passes together 5 minutes?  And how do you combine them?

The problem also is you usually don't have only reflection and 
refraction but also a diffuse part.

> I've posted three images in povray.binaries.images demonstrating the 
> traditional method and the two new methods.
> 

Were not viewable here.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 21 Mar. 2004 _____./\/^>_*_<^\/\.______

Post a reply to this message