Water - SSS Problem, VRay 1.47.03

[UnAion]

Hello

I'm having some problems when using SSS with transparent materials, like water for example. I made a very simple scene as I wanted to get more familiar with SSS in VRay, but I think the results I'm getting looks weird and not as I would expect. The way I would expect it to look is that the refraction isn't changed, only the distribution of light within the water, but this may not be correct..

In the picture with water and SSS, it looks like the box with the check texture disappears completely under water. As does the pool wall at the upper right part and the red sphere looks a bit squished. In the pictures below the IOR was 1.33, I also tried to render with IOR at 1, but I couldn't see any difference when using SSS.

In the help index I see that "Currently VRayMtl supports only single-bounce scattering", could this be the cause? If so, there may not be any solution to get a more realistic look..?

It would be great if anyone knows what the problem is, I may be doing something wrong as I haven't used SSS a lot. Thanks in advance


My scene looks like this with no water:




This is how it looks with water and no SSS:




When I turn on SSS I get this:




There is no GI used, only a VRay dome light and a omni light with VRay shadows. This is my material settings and a view of my (very complex) scene:



EDIT: Should maybe say that I'm using 3ds max 8 with SP2 and VRay 1.47.03

[Morbid Angel]

it is possible to get the effect you are looking for, but I think not with sss but rather with glossy refraction and fog. There was a tutorial a while back about it, i cant remember where it is now...

[UnAion]

Yes, I have also seen some good tutorials about similar effects with just glossy refraction and fog. However, I'm wondering why I can't get this result with sss, is it because of some limitations when using sss? Some time ago I remember Vlado posted a short animation/pictures with a very nice water material, were sss was used. But I think the sss algorithms was changed some time after that, maybe sss doesn't work so good with these kind of effects currently.

[andrewjohn81]

be warned. Don't use Light Cache if you are using glossy refractions.

It'll look fine for some frames, but others render dark and with most of your materials returning overbright which will cause green. Lots of green.

[UnAion]

Ok, thanks for the tip! But in this case I don't use GI at all, so that shouldn't be the problem here. Is the way translucency work now just ment to be used on skin, wax and other non-see-through surfaces?

[AJ Jefferies]

But in this case I don't use GI at all, so that shouldn't be the problem here.

As far as I'm aware translucency/SSS won't 'bounce' at all without GI. I could be wrong, but I've always had GI enabled when working with SSS.

[UnAion]

I didn't think of that, good point I now tried to render with GI (Irr map medium preset + QMC, refractive GI caustics enabled), and I still got the same problem:



To me it appears almost like if the water would be non-transparent, with everything under water projected straight up and used like a texture on the surface, hiding any vertical underwater areas. Any suggestions/thoughts?