Scene that makes AlSurface super slow

[LudvikKoutny]

Hi,

when creating one of my latest scenes, I tried to use AlSurface for snow, and everything was going fine right up to the point where AlSurface brought scene speed down to crawl, when I applied it on one specific mesh. It seems I've accidentally discovered a rare combination of using AlSurface, Environment Fog, VraySun and a mesh of very specific character, which together makes AlSurface very slow. When I swap the material for FastSSS2, everyting runs perfectly, although FastSSS2 with true raytraced SSS seems to be generally slower than AlSurface.

I am attaching the scene below:
https://dl.dropboxusercontent.com/u/...surfaceBug.zip

Max 2016 SP3 + V-Ray 3.50.02 beta2

[LudvikKoutny]

Hi, any news on this? I would really love to use AlSurface instead of FastSSS2 as provides both visually more appealing SSS as well as faster rendertimes. But this is giving me a hard time.

[vlado]

I somehow missed this, thanks for reminding me.

Best regards,
Vlado

[vlado]

The slowdown is because of the environment fog; for some reason it switches to raymarching even though there are no textures attached. I'm looking into it. One way to render something out for now is to set the environment fog subdivs to 1.

[EDIT] It's because of the falloff radius which causes the environment fog to switch to raymarching. Like I said, setting the subdivs to 1 will make it go faster for the time being, but it's something that we need to improve definitely.

Best regards,
Vlado

[LudvikKoutny]

Oh, sorry, I apologize. I remember testing if raymarched volume with very large steps (just below the threshold where artifacts would start to show up) would by any chance be faster than stochastic volume sampling, and I was stupid enough to forget putting it back, and then wrongly attributed the slowdown to Alsurface.

My bad, and sorry for wasting your time

[vlado]

No worries

Best regards,
Vlado