Appendix:Substrate Materials

We can almost consider our section on Materials complete. But wait, why did I say almost? Well, that’s because everything explained so far is related to traditional or legacy Materials. Starting with UE 5.2, an entirely new type called Substrate Materials has been introduced. They are truly innovative, and they are poised to eventually replace the current Material system. However, this is more of a long-term goal, and the current Material system will likely remain as an option. As of the current version, UE 5.3, the traditional Material system is still the default and official system, while Substrate Materials are experimental, not even in beta, which doesn’t make it very clear how or when this transition will happen.

For these reasons, I believe it’s worth introducing these new Materials now, even though you may not use them for production any time soon. Even the official documentation encourages experimentation but not shipping...

Overview

The Substrate system in UE 5 revolutionizes Material authoring by replacing fixed shading models such as Default Lit and Clear Coat with a versatile, modular framework: Materials are represented as “Slabs of matter” using principled BSDF parameters with well-defined units. These Slabs form a graphical network where operations such as mixing and layering occur.

Overall, Substrate addresses the limitations of legacy UE shading models such as Default Lit and Clear Coat, allowing for smoother transitions and layering across meshes, overcoming issues such as whitish artifacts during Metallic parameter blending.

How it works

The system is fundamentally built upon components called Slabs, which have a direct connection to physical reality. A Substrate Slab is composed of two essential elements: the interface and the medium.

Figure Appendix.1: The Slab’s composition

• The interface represents the boundary where light interacts...