Simulating partial occlusion in post-processing depth-of-field methods

Faster methods are based on the idea of using rasterized images and simulating DoF via post-processing. The first to discuss such an approach were Potmesil and Chakravarty in 1981. Based on the parameters of an optical lens, the diameter of the blurriness, the so-called circle of confusion (CoC) for an out-of-focus fragment at depth z can be calculated as dcoc(z, f, N, zfocus) = |||| f2 (z - zfocus)z N (zfocus - f) ||||, (2.1) where f is the focal length of the lens, N is the f -stop number, and zfocus is the distance to the focus plane [Potmesil and Chakravarty 81]. Note that Equation (2.1) is based on a thin lens model, which is sufficient for simulating DoF. To simulate DoF, each fragment in the rasterized image is blurred according to its CoC in a post-process.