ABSTRACT
The appearance of an object depends on the response of the light reflected from its surface to the eye of the observer. For the purposes of photorealistic rendering, surface reflection was typically regarded at two levels: the macrostructure of an object refers to the basic visual geometry; the microstructure is the microscopic detail that affects light reflection, e.g., surface roughness and microgeometry, but the detail itself is not actually visible. The representative example is the combination of BRDFs and global illumination: BRDF models depend (implicitly, at least) on the microscopic detail of the surfaces; global illumination simulates light transport at the macroscopic scale.
