How to properly combine a Skin (Subsurface) Slab and a Transparent Slab using Substrate Horizontal Blend while preserving SSS?

Development Asset Creation
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Hi Epic Team / Substrate experts,

I am working on a character material in Unreal Engine using the Substrate framework. My goal is to create a hybrid material where part of the surface is skin (using Subsurface/Diffusion) and part of the surface is transparent/clear (using a mask via Substrate Blend).

Here is my current setup (as shown in my material graph):

  1. I created a skin Substrate Slab connected with Base Color, Roughness, Normal, and MFP / Subsurface parameters.

  2. I created a transparent Substrate Slab for the other part.

  3. I blended them using a Substrate Blend node driven by a black-and-white mask texture.

The Problem I’m Facing: When I change the global Material Domain/Blend Mode to Translucent to accommodate the transparent part, the Subsurface Scattering (SSS) effect on the skin portion completely disappears or breaks, acting as if the skin SSS parameters are ignored by the transmissive pipeline.

My Questions:

  1. What is the official recommended workflow in Substrate to blend an opaque/subsurface material (Skin) with a transparent material on the same mesh?

  2. How should the global Material Settings and Lighting Modes (e.g., Translucency Lighting Mode) be configured so that skin SSS and transparency can coexist without breaking each other?

Any advice, documentation references, or best practices would be greatly appreciated. Thank you!

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I don’t think it would be possible. Substrate or no, each material slot on a mesh would be rendered from the same draw call, which would usually mean the whole shader needs to have the same blend method/domain. As such, to use both subsurface and translucency on the same mesh (like a human with a glass shelled cyber arm), you’ll probably have to do it the old school way and assign a separate translucent mat to the glass faces of mesh.