Technology for 3D scanning has come a long way, but the authors of a technical paper from the University of Southern California’s Institute for Creative Technologies featured by Prosthetic Knowledge explains that the scanning only captures things at the surface level.
According to the authors, 3D scanning is unable to capture the complex “microstructures” that are over 1/10 of a millimeter below the skin’s surface. The end result is something is skin that doesn’t look very realistic when the skin is wrinkled up or stretched out. In fact, it can be a bit off-putting.
There is an explanation of how the microstructures have specific markers that are important to determining a person’s facial expressions. Luckily, they have figured out a way to map a high-resolution displacement map onto a surface to create a simulated version of our complex epidermis:
When skin stretches, the microstructure flattens out and the surface appears less rough as the reserves of tissue are called into action. Under compression, the microstructure bunches up, creating micro-furrows which exhibit anisotropic roughness…
We approximate the skin being flattened under stretching, and bunched up under compressions by convolving a 16K displacement map. We blur the microgeometry displacement map in the direction of stretching, and sharpen it in the direction of compression using the surface normal distribution histogram as a guide. This entire computation can be efficiently implemented on GPU shaders.
Source: gizmodo