Fast subsurface light transport evaluation for real-time rendering using single shortest optical paths

To synthesize photo-realistic images, simulating the subsurface scattering is highly important. However, physically accurate simulation of the subsurface scattering requires computationally complex integration over various optical paths going through translucent materials. On the other hand, the powers of light rays are immediately decreased when they pass through limitedly translucent materials. We leverage this observation to compute the light contribution approximately by only considering a single ray that has the most dominant contribution. The proposed method is based on an empirical assumption where the light ray having passed such a dominant path has the largest influence for the final rendering result. By only considering the single dominant path to evaluate the radiance, visually plausible rendering results can be obtained in real-time, while the rendering process itself is not based on the strict physics, nevertheless. This lightweight rendering process is particularly important for inhomogeneous translucent objects that include different translucent materials inside, which have been one of the targets that is difficult to render in real-time due to its high computational complexity.