Path Tracing

Path tracing is an algorithm for image synthesis, which enables the simulation of global illumination.

Path tracing is based on the recognition that the simulation corresponds to the global illumination rendering equation in solving the so-called, which indicates the density of any radiation, from a certain point the outgoing light beam.

Path tracing using rigorous mathematical methods, which originate from the field of mathematical statistics. The algorithm uses a so-called Monte Carlo integration in order to solve the rendering equation approximation. Therefore, path tracing, as well as more extensive, as related algorithms such as Metropolis Light Transport or Bidirectional path tracing, also known as Monte Carlo ray tracing.

In path tracing, each ray that is shot into the scene, reflected upon impinging on surfaces, broken or absorbed each time (except in the case of absorption ) at least one random beam is generated, which approaches the integral of the rendering equation. The initial beam seeks out so its way (path ) through the scene. The more top -rays are used, the more one approaches to the ideal image. The error of the approximation expressed as variance, which corresponds to image noise. Techniques such as importance sampling contribute to the reduction of the variance.

The difference to diffuse ray tracing is that the path tracing the full render equation using randomly generated rays at all - is dissolved surfaces, thus simulating global illumination - even at diffuse.

In practice, a pure path tracing is often too slow, which is why it can be combined with photon mapping.

The idea for the path tracing was published in 1986 by Jim Kajiya, along with the rendering equation as SIGGRAPH publication, at that time under the name integral equation technique.