Chaos Corona for 3ds Max > [Max] General Discussion

Material reflections & max sample intesity

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cgrobo:
I ran into a strange issue with a completely non reflective material. The dark ball has both reflection and reflection glossiness set to 0, yet it seems to be receiving light from the chrome material (red arrows). Setting the max sample intesinty to 1 seems to get rid of this issue, however I assume changing this value to 1 in other rendering situations won't work.


The effect is even more pronounced with a glossier material/ball (pic 44, 55 and 66)


Why is this happening?

pokoy:
I think these are GI caustics, sort of non-sharp caustics coming 'for free' with the rendering method. You can probably get rid of these when you use a rayswitch material and use a non-reflective material in the GI slot (or both reflected and GI).

Nejc Kilar:
Yep, this to me looks like the usual and expected reflection behavior.

When the surface is not glossy it will bounce rays all over the place basically whereas with the glossy material they'll be more focused and that will make a bigger, more visible impact on things. When you limit MSI you're basically saying "hey, those really strong rays should be clipped" and as such you're then not getting them to come though.

cgrobo:
Appreciate the replies. How come this "expected behaviour" doesn't occur in Fstorm? If it does, it doesn't look smudgy. Attaching images.

pokoy:
I may be wrong but the metal needs to be less blurry and probably needs the same amount and rotation/angle of anisotropy (which will play a role in how the light is reflected on the surface).
Thinking of anisotropy, this is probably contributing to how 'smudgy' it looks. But the reflecting mirror material should be as close as possible to compare.

That said, BRDF models probably aren't the same for both renderers, so differences are to be expected. Again, you might want to try the Rayswitch mtl wrapper if you run out of patience.

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