When and when NOT to use multiple importance sampling & multi-scatter GCX?

Support Materials and Textures
1

I understand these features will kill noise but also increase render times.

I know what they are, but I’m curious when I can disable them with none to minor differences to the result so as to reduce render times?

2

For high refraction roughness and SSS, you must use Multi GGX. If not, your result will be dark and energy conservation will looks problematic.

Multiscatter-GGX tries simulate micro reflections.

2259×1080 170 KB

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3

So basically anything much above .5 roughness, or the sss/refractive materials? Ok, I can totally optimize that…

Very helpful!

Any idea on the multi importance option on lights?

4

If you need, you can use for Glossy roughness. But for SSS and Refraction you really need this.

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5

I’ts not that you “must” use multiscatter everytime you have high roughness, you use it when the energy loss is too much, or destroys the image. I’ll typically don’t use it for high roughness dielectrics except glass. I rarely deal with very high roughness metals, but it would have impact and I might consider it.
I use MIS on the lighting that is responsible for lighting up the scene, and turn it off for very local lights or indicator style lights that doesn’t light up the scene. For a big TV I might turn it off for a daylight scene, and on for a nightlit scene with dimmed lighting.

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