In the video above, the tricycle on the left contains eight individual material elements, with five unique materials placed within those slots. The one on the right utilizes material layers, which blends materials together to a single asset that can be applied, shared and reused as needed. Developers can use the single material approach, layered materials, or a combination of the two depending on their preference.

This evolution in materials is especially significant because layers can now be painted on at the pixel level, as opposed to the traditional method of applying changes to individual polygons. This can save loads of man hours, especially because UE4 assets can be edited, saved, and shared on the fly.
Since materials can now be mapped per-pixel, artists have the ability to change that mapping at runtime. This technique yields materials that are inherently simpler because they can be created faster and are easier to edit down the pipeline, if necessary.

Lastly, the mask that defines each material layer’s placement can itself be modified and animated during gameplay. The potential applications that take advantage of this perk are limitless: Consider torn fabric exposing the skin beneath, or streaming liquid across a character’s flesh. Artists can even simulate character morphing by switching to a completely new type of material, such as shifting skin to steel or chrome – all changing at runtime, and all while maintaining fast and efficient editability for artists. We hope you enjoyed our first entry in the series. Stay tuned for new videos from our developers!

Source