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View Full Version : What does Raytrace Occlusion do?



lertola2
12-02-2011, 08:54 PM
I do not know what the Raytrace Occlusion check box on the Render Globals panel does. I have never noticed a difference in any renders weather this button is checked or not. Does anyone know what this control does and what it is useful for?

Thanks,
-Joe

probiner
12-03-2011, 12:17 AM
Until someone with a better in depth answer shows up: http://www.except.nl/lightwave/RadiosityGuide96/index.htm

lertola2
12-03-2011, 07:00 AM
Until someone with a better in depth answer shows up: http://www.except.nl/lightwave/RadiosityGuide96/index.htm

Thanks but Raytrace Occlusion is not mentioned there. It did discuss the Ambient Occlusion check box on the Global Illumination tab which I also was in the dark about.

I did find the description in the whats_new_lw95.pdf:



Ray Trace Occlusion
Allows you to enable occlusion when the ray recursion level is reached. If the ray is occluded, the background will not be seen by the ray. This should work for all reflection, refraction, transparency and dissolve rays regardless of their origin (LightWave, plug-ins or Node Editor). Rays can be partially occuded when they pass through partially transparent or dissolved surfaces. Occlusion also considers clip maps. Ray Trace Occlusion will save users from having to create reflection masks to remove the background from areas where it should be blocked by other objects.


It is nice to have the description but I don't feel much enlightened. I will have to do some tests to see what the effect of this setting is.

-Joe

lertola2
12-03-2011, 05:04 PM
I ran a test render with Raytrace Occlusion on and off. Except for the floor the objects are completely reflective. With Ray Recursion Limit set to 1 you can see a difference in the renders. The higher the Ray Recursion Limit the less the difference. In this case the render was faster with Raytrace Occlusion on.

So I think the conclusion is that this setting only has an effect if there are reflective or refractive objects in the scene. Raytrace Occlusion does not seem to be any performance penalty so there I think I will always turn this option on.

-Joe