Here is an example of a real-time "feather groom effect" which consist of spawning feathers on the surface of a skeletal mesh, similar to fur/hair grooming techniques used in movie CGI and games. The difference here is that every feather is a planar-aligned billboard particle, which then can be controlled via usual particle-level scripting. This allows effects like this "Mystique-like" change of skin between one side of the feather and the other.
Unreal Engine 4
Rendering inside Unreal Engine. Both materials are set-up inside a unique graph.
Switching between the two sides is done with shape sampling: here we are using a simple sphere as our driver, and evaluating a distance field for each particle. If the particle is close to the sphere, it will begin to shift from feather-like shading to a "golden" state.
On top of that, things like feather placement, alignment/flow along the body and feather size modulation are achieved by using mesh-based data like tangents/bi-normals but also vertex colors.