color (hue) of material shifts at higher resolutions.

[Mayohorn]

Hello and thanks for taking time to view my post.

I am new to V-ray and I would put my experience level at medium for maya and mental ray with several years experience.

I am having a pretty frustrating problem where the color of my model will start to shift when i start rendering at resolutions of 1024 or above. The higher res i render at, the worse the problem is. To be specific, the skin tone on my character is that of a caucasian, light red/yellowish. However, when i do a large render the skin turns yellowish. The rest of the characters body is a vibrant blue color and does not seem to change. Only the skin. Does anyone know the cause of this? I have tried using different lights, (mental ray and vray), and different cameras.


Also if it matter, i am on windows 7, maya 2015, newest vray, gtx titan black video card, intel 6 core processor

[t.petrov]

What materials are you using?
What GI?
Does this problem happens with a simple scene?

[Mayohorn]

Thanks for the response.
I will have to check the material when i get home however, it is some kind of Vray material, which i am unfamiliar with, as i no next to nothing about vray :/ I didn't create the model, i was just contracted to for posing and rendering for marketing purposes.

Im not sure about GI, (Global illumination?) I didnt know there was more than one kind. I will try to post some pics of my render settings and my material network.

And by simple scene you mean what exactly? Right now my scene consist's of 3 lights, 1 character, and an small ground plane with primary visibility turned off.


Thanks

[t.petrov]

Im not sure about GI, (Global illumination?) I didnt know there was more than one kind. I will try to post some pics of my render settings and my material network.

Yes there are many combination for GI solutions. See this page for details: http://docs.chaosgroup.com/pages/vie...pageId=5080973

And by simple scene you mean what exactly? Right now my scene consist's of 3 lights, 1 character, and an small ground plane with primary visibility turned off.

A scene containing only simple objects - cubes, spheres, materials and lights.
Most of the times simpler scenes can be shared more easily (no nda or similar concerns).
But if you can share the scene with us we can probably investigate what the problem is.

[vlado]

It probably has to do with the skin shader; if you are using a prepass-based SSS, it might make sense to try the raytraced one.

Best regards,
Vlado

[Mayohorn]

Thank you T.Petrov and Vlado for your responses. I figured out the problem, which of course makes me feel a bit dumb as it was one of the first settings i played with on the skin shader. The "scale" was set to 1 which seemed to intensify the saturation. Im not sure what that even is but, when i took it all the way down to the lowest level it seemed to fix the problem.

[vlado]

But doesn't that also kill your SSS effect? I'd say go with raytraced multiple scattering - it should be a lot more consistent.

Best regards,
Vlado

[Mayohorn]

Sorry I have been MIA on this topic for so long. Vlado you were correct about changing the Multiple Scattering option. However i found the "object-based illumination map" to work best. I cant really see much of a difference in the SSS effect when i lower the Scale so i decided to keep that lower. I also played with the Overall color and Diffuse color to help with the hue and brightness of the skin.

I am still having one issue with this SSS material however where its getting blown out due to a strong key light. Because i would rather not set up a complex lighting scenario with light linking to certain objects and what not, im hoping there is a way to use the existing light set up and reduce the specularity of the highlight in the skin shader's options. In essence, to get a more "lambert" look. So far I have not been able to achieve this. Any help would be appriciated.

Thanks,
J

[Svetlozar Draganov]

I am still having one issue with this SSS material however where its getting blown out due to a strong key light. Because i would rather not set up a complex lighting scenario with light linking to certain objects and what not, im hoping there is a way to use the existing light set up and reduce the specularity of the highlight in the skin shader's options. In essence, to get a more "lambert" look.

Would it be possible to share the scene and the result you've got so far?

[Mayohorn]

I really wish i could, as it would make all this easier. Unfortunately the model is from Sega and can't be shared.

[Svetlozar Draganov]

Perhaps you could replace the model with another geometry or a simple primitive while the issue is still present?

[Mayohorn]

Im not sure that would help as i think its more of an issue with the sss shader itself. Again im just trying to give it a more lambert like look to avoid hot spots of direct light

[Svetlozar Draganov]

We need to address the issue in order to provide a solution about it - that's why we need a simplified version of the scene.
To make SSS material more lamber appearance try to decrease Specular Amount and Specular Color Value parameters: