vray mtl sss blend material not working

[AyrtonSenna]

Hi,

using 2 vray materials in sss mode wont blend with the blend material?
using vray dirt for the blend. But even with the grey color swatch to black or white will just show only the base material not the coat.

greets

[vladimir_krastev]

Hi. thanks for posting. Have you tried to use the two materials as coats instead of base and coat?

[vladimir_krastev]

I made a test scene with two VRayFastSSS2 coat materials and VRayDirt as a mask. Please check it out and let me know what you think.

[winberg]

I was about to post the same problem, unsure if the problem was with fastSS as shown in the file uploaded by Vladimir, but trying to blend two vraymtl with SSS (no transparency) just gives wierd results.. Is there a trick to this?

-Tom

[vladimir_krastev]

Hi, using VRayFastSSS2 as layers in blend material works as expected. Could you show us an example of your setup with the VRayMtl?

[winberg]

Its The standard VRayMtl with «sss» in two different materials blended with a bitmap mask, so not the fastsss.

[winberg]

I am aware that this have not been possible in the past, but I was hoping that with the last change, this would be adressed in the newest versions.
All the settings are mappable, so technically I can make a blend inside the material. So in my mind blending two materials should technically be the same?

[vladimir_krastev]

Hi, a refractive material that uses SSS translucency has to be used as a base material only. It won't work well if used as a coat in a VRayBlendMtl. Could you show us an example scene that shows your setup and what is the final look that you are after? There could be another approach available.

[winberg]

When making a material with mapped different sss settings (and other settings) in the same material, things start to get complicated when adjusting and testing.

The the attached image shows in principle what I am talking about.

Two simple materials with sss that I would like to dump into a blend map with a mask. - I can get the effect that I am after by mixing the different settings with a mask.
Since this is doable inside the material, my thinking is that this should also be possible with a blend material, maybe with a "special" blend material? a checkbox for something?

-Tom

[vladimir_krastev]

Hi, thanks for the example. A material with SSS translucency won't work if used as a coat. Here is an older thread you might want to read where a similar setup is discussed but with the same success.
One thing I tested now is to use the VRaySwitchMtl instead. It seems this might work but it does not work with the smooth transition of the Gradient Ramp map.

[winberg]

yes, I have been working around the problem for quite some years now, Resently switched from an older version, and was kind of hoping that this would be "fixed" now. I realize that there might be some limitations.
But as I mentioned, you can map all the slots now, so it should be possible to blend to materials with a mask, when this is possible inside the material - just my non programmer logic I guess.

-Tom

[winberg]

I tried more or less the same thing in Arnold, I have no experience with this render, but managed to make two sss materials and blending these with the "layer shader" (I have no idea if this is correct, but it seemes to work). Can we have another type of map blender maybe? where this is possible?

-Tom

[vladimir_krastev]

managed to make two sss materials and blending these with the "layer shader"

You can do the same in V-Ray by using the FastSSS2 material but not with a VRayMtl that uses sss translucency. It is not the same thing.
Here is the VRayBlendMtl with two FastSSS2 materials blended with a gradient map:

[winberg]

I know that I can blend two fastsss materials, as you have pointed out. I also know that blending two sss translucency materials does not work.
All I want is some way to make this work - A 2d image blend hack? - I work around this by rendering two materials, and doing it post. It would be nice to do in the renderer.

-Tom