Future of SSS Shading

[sdelalla]

Hi Chaosgroup,

I was wondering if you all can shed some light on your future plans for SSS materials. The current landscape between ALSurface and FastSSS feels rocky. Neither materials have support for the same specular controls that are available on the Vray Material (glossy fresnel, metalness, ggx tail fall off). What ends up happening quite frequently is we create a SSS material with no reflection as a base material, and then blend it with a Vray Material to use the reflection there. ALSurface has nice specular control with the second coat layer and individual bump control, but with its lack of metalness support it makes it less friendly for assets that we are converting for real time applications.

This brings up a few questions:
Should we expect ALSurface to be the default SSS shader?
Are there any plans to add better specular controls to fast SSS?
Are there any plans to add the functionality of the fast SSS directly into the Vray Material?

Overall it feels like Vray has all the pieces floating around, but not a clear path forward.

On a related note, it would be nice to have a second reflection lobe on the vray material, I am sure you guys hear that a lot.

Thanks for any info you can provide related to the topic and for listening to the feedback.

[yolov]

Hi and sorry for the late reply.

It's a bit hard to recommend a go-to SSS shader without going into some details. I hope I'll be able to give you some insight about future development in my answer below.

Both AlSurface and SSS2 can be (and are) used for skin. AlSurface allows for greater control with multiple SSS and specular layers, while SSS2 is much simpler. In this context, AlSurface is suitable when going after higher visual fidelity, and SSS2 might be a better choice for simpler and quicker setups, while still allowing for convincing renders.

We do plan to update VRayMtl with an extra coat layer (secondary lobe) among other things. For example, we'are adding a sheen layer to better represent cloth. While we have sheen working internally, it still needs some work. Next, we'll add a coat layer, and we also want to update the SSS layer of VRayMtl, although the time-frame for the SSS layer is a slightly further down the road than the coat layer.

With all this in mind, we do plan to keep improving all 3 shaders, where some improvements are on our short-term roadmap, while others still need some research.
If some of this is more important to you than another, or if there's yet another thing you need, do share with us, we'll appreciate it.

[sdelalla]

Thank you Alex. It is great to hear about the future plans. Having the secondary reflection lobe and sheen would definitely be most important to us. Many of our materials have complex specular setups, and some artists end up doing this incorrectly with additive materials ( this a training issue, but hopefully shines light on how the entire shading workflow could be simplified).

As far as the SSS on the Vray material, personally I feel like this would be the best path forward. Something we end up needing to do frequently is blend Vray anisotropic highlights with ALSurface of FastSSS, and this could be simplified all down to one material.

We do sometimes utilize the individual bump controls on the AL Surface specular, so this would also be a nice to have feature built into the Vray material. It would be nice to have the ecosystem fully revolve around a single material.

Thanks for listening.