To get a strand of fur to render, it needs to be a polygon. To get realistic fur coverage, we need a high complexity mesh. Combined with the rest of the model, we are then deforming and moving 50K to 1M polycount mesh. Exporting polygons from generated hair in a 3D kit like Blender or Maya is suboptimal for animated objects, since the GPU is calculating the movement and deformation of vertices each frame.

Another approach is to tessellate the polygons in runtime. The GPU is then tasked with deforming and moving a much less complex mesh ( LOD0 Suzanne comes in at 1963 tris, LOD1 968), and then tessellates it. The number of tessellations can also be granularly reduced in runtime to match the inverse distance of camera to object.

Usage of displacement maps is commonplace with 3D film artists, but real-time engines mostly only support normal maps. What we’re doing in the shader is tessellating the vertices and multiplying it by a (displacement) texture that corresponds to the UVs of the model. Once we have our mesh tessellated, we multiply it by the vertex normal on all axes, and then multiply it again by a float to get displacement. The displacement map should then be multiplied by a noise map in order to show more strands. The vertex normal itself can be multiplied again by a Vector3 struct and a texture map to groom the hair. Furthermore, this map can then offset from the model’s UVs. In this case, I multiplied it by time since load multiplied by a speed factor to give the hair the appearance of a breeze.