Visually, these side by sides bear a lot of resemblance to the spatial and frequency domains from the sampling lecture. I wonder if these two concepts have more than just a visual relationship and that anisotropic materials have certain rendering optimizations that isotropic materials do not have due to smaller variance in brdfs.
I'd heard of anisotropic filtering before but never thought to look it up. Wikipedia says it's "a method of enhancing the image quality of textures on surfaces of computer graphics that are at oblique viewing angles with respect to the camera where the projection of the texture appears to be non-orthogonal." Seems potentially relevant?
^ Going off of this, the non-orthogonality seems related to the velvet example in a later slide. How are these non-orthogonal projections calculated?