Controlling Thin-walled translucency in Comp

[Xntric]

Hi,

I was wondering what is the correct way or most efficient way to have control over Thin-walled translucency for foliage, for example.

what renderelements and what formula to use?

[vladimir_krastev]

Hi, thanks for posting. You could use the VRayRefraction. It is best to avoid changing too much the translucent foliage in post production.

[Xntric]

AFAIK the thin walled translucency is not included in the Refraction pass, only real SSS translucency seems to be

[^Lele^]

Could you be a bit more specific, f.e. sharing a shader and the exact kind of results you'd like to obtain in post for it?
Regardless, the thin-walled SSS is stored in the VrayLighting RE.
If you use a backToBeauty RE you can easily tell where everything is.

We're investigating if this is the wanted behaviour or a bug.

[Xntric]

So imagine a simple thin walled foliage shader using the thin walled SSS option.
I was wondering if there was a way to control thin walled SSS amount in post and the color of it?
Seems to me that Lighting pass would affect lot more than just the translucency effect, but i will try to play with it.

Scenes with many different foliage assets can be cumbersome to go through each shader and tweak it, so it would be handy to control it in post
It's not necessarily a feature request more just wondering what the smartest way would be to go about it or if its possible at all?

[Joelaff]

A VRayExtraTex of your translucency map limited to the specific objects could be used combined with LightSelects (or LightMix). It still does not isolate the translucent from direct shading of course, but it would give you some control, as oftentimes the back light is separate form the front light anyway.

Speaking of that you might also want to add a VRayExtraTex with Shadow/light Falloff setup, thus being able to control the translucency tweak in the darker areas (in terms of front lighting), where you would see it most. Could also experiment with VRaySamplerInfoTex with the Refraction Vector output, and adjust the IOR to taste.

Like anything in post (and most things in 3d) these are all cheats, and may not be physically accurate, etc. But they may solve a need in production.

Of course getting the translucency in a Render Element would be awesome for this....

[^Lele^]

So imagine a simple thin walled foliage shader using the thin walled SSS option.
I was wondering if there was a way to control thin walled SSS amount in post and the color of it?
Seems to me that Lighting pass would affect lot more than just the translucency effect, but i will try to play with it.
Scenes with many different foliage assets can be cumbersome to go through each shader and tweak it, so it would be handy to control it in post
It's not necessarily a feature request more just wondering what the smartest way would be to go about it or if its possible at all?

Amount no, unless you render the materialselect without the SSS to blend it back in with the SSS one.
The color it's no issue (ofc you're expected to have an object/material mask to go with your various shading REs): you can use a mtlselect, extract the shader, minus the specular from it, and tweak colors away.
Notice that many different foliage assets will definitely require more care: perhaps cryptomatte may come in handy if they are just too many to manually split via Multimattes (although there are scripts for it, it can become a very thick EXR to manage.).

We are on the case to see what can be done for the destination RE.

[Xntric]

A VRayExtraTex of your translucency map limited to the specific objects could be used combined with LightSelects (or LightMix). It still does not isolate the translucent from direct shading of course, but it would give you some control, as oftentimes the back light is separate form the front light anyway.

Speaking of that you might also want to add a VRayExtraTex with Shadow/light Falloff setup, thus being able to control the translucency tweak in the darker areas (in terms of front lighting), where you would see it most. Could also experiment with VRaySamplerInfoTex with the Refraction Vector output, and adjust the IOR to taste.

Like anything in post (and most things in 3d) these are all cheats, and may not be physically accurate, etc. But they may solve a need in production.

Of course getting the translucency in a Render Element would be awesome for this....

Sorry for late reply, i have been so caught up with my graduation project.
I'll try to include these vrayExtraTex passes in my final rendering now

Thanks!

[Xntric]

Amount no, unless you render the materialselect without the SSS to blend it back in with the SSS one.
The color it's no issue (ofc you're expected to have an object/material mask to go with your various shading REs): you can use a mtlselect, extract the shader, minus the specular from it, and tweak colors away.
Notice that many different foliage assets will definitely require more care: perhaps cryptomatte may come in handy if they are just too many to manually split via Multimattes (although there are scripts for it, it can become a very thick EXR to manage.).

We are on the case to see what can be done for the destination RE.

Yeah using cryptomatte by mtl and vraylighting pass should be able to get me far, was just curious whether there was a method for translucency i didnt know about. Thanks for the tips