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View Full Version : 'Ray Cutoff' feature description?



toby
08-11-2011, 08:15 PM
It's in render globals but not in the docs.

I assumed it was based on color value, not reflecting any value below the threshold you set; which would save render time.

But it seems to reflect any value no matter how dark and no matter how high the threshold - so I guess that's not it. The default of 0.01 would be too high anyway.

Anyone know what it does?

Celshader
08-11-2011, 08:36 PM
It's in render globals but not in the docs.

I assumed it was based on color value, not reflecting any value below the threshold you set; which would save render time.

But it seems to reflect any value no matter how dark and no matter how high the threshold - so I guess that's not it. The default of 0.01 would be too high anyway.

Anyone know what it does?

From what I remember, the ray will not bounce any further if the latest bounce returned less light than the value defined by Ray Cutoff.

Here's some more definitions:


From http://news.creativecow.net/story/861205

Ray Cutoff Enables artists to decide at what point to cease ray bounces when rendering a scene with numerous reflections, refractions and transparency, significantly shortening render time



From http://newtek.com/forums/showthread.php?t=88597

Implemented changes to raytracer to improve detection and early termination of rays that will not affect shading, which should provide speed improvements in some situations. The control is on the Render Tab of the Render Globals panel, "Ray Cutoff." The default is the recommended setting of .01, which provides much faster rendering with little to no impact on quality. Setting this to 0 will make the renderer perform as it used to; setting it higher can gain further speed, with a tradeoff in rendering quality.

toby
08-11-2011, 09:37 PM
Thanks Cel

Yes that's what I was trying, but was still getting reflection of .01 r,g, and b with the ray cutoff set to 10.0.

On the chance that ray cutoff works in hexidecimal color I set it all the way up to 255. It really shouldn't reflect anything at that point, right? It still does, even as dark as .0075, but is it stopping the ray recursions sooner than where I have that set. But it cuts the ray recursions short at bright colors too, so I can't find a correlation.