Ah, fur. Just so you guys know, this is one of the most complicated shaders you could ever make… ever. Very few games use fins and shells because the overdraw is so great. You need a lot of geometry to make the effect look convincing, and you also need a ton of shell layers: way more than what would make a convincing parallax occluded material, because you need to connect very small, fine points. This effect looked very convincing on consoles like the Gamecube and PS2 which had low screen resolutions and large parallel pixel shaders, but it is significantly more difficult to make the effect look convincing on higher resolution screens. You will waste your entire pixel rendering budget on making those shells. You might as well forget this as a mobile feature. There are other methods, however, to handle hair, fur, and generally soft bodies.
Alpha cards render extremely well. You get the flexibility of full-scale materials with the artist-defined cutout of the hair cards. Unfortunately, UE4’s transparent rendering is not compatible with the deferred lighting shader, so you will need to use cubemaps in the material itself to simulate transparent lighting. If you can find a way to blur the cubemap for a softer reflection, let me know, because I would love to know how to do this! If you use a sharp mask you can get access to deferred lighting and the roughness settings in the material, but you’ll need a higher texture resolution to ensure you don’t have floating hair. Also, good luck getting the cards to stay where they need to be with rigging. If you can pull it off, it will cost a lot of vertices and there will be overdraw, but not nearly as much as shells and fins. The end result is not perfect, but the best in a realtime CG environment.
The next method is to use fuzzy shading: a simple fresnel-based algorithm that generates a soft light outline around the edge of the model’s falloff, simulating the effect of hair catching light off the model’s surface. It’s generally good for velvet materials, but you can’t get individual hairs using this method.
Real video games nowadays like Super Smash Bros. 4 use a combination of the above two methods to simulate fur on characters like Fox and Donkey Kong. Rarely will games make the jump to full-blown fur shading due to its complexity and expense. Donkey Kong: Tropical Freeze actually uses fins and shells, and older games like Kinectimals also used it, and the effect is largely successful. But once again, this is definitely not a mobile-ready feature. If you choose to use it, it will be just as expensive as rendering a AAA-quality ocean shader layered over the ground underneath, and if you don’t maintain some control the camera, it will easily fill the entire screen, causing massive and erratic rate drops over your entire project as the pixel and vertex shaders try to pump out a complex multi-layered transparency shader. If you can pull it off, please let us know how you managed, because a practical solution for this will be a Godsend. I would totally pay for it if it was on the Marketplace.