Path tracing

Path tracing is a rendering algorithm in computer graphics that simulates how light interacts with objects and participating media to generate realistic, physically plausible images. It builds on earlier, more limited ray tracing algorithms and is used to create photorealistic images for artistic purposes, for architectural rendering and product design, and for frames of animated films and visual effects. Because it can be very accurate and unbiased, it is commonly used to generate reference images when testing the quality of other rendering algorithms. The technique describes illumination in a scene with the rendering equation and finds an approximate solution with Monte Carlo integration: it traces a ray from the camera, lets it bounce in random directions off objects, and computes the light carried along the path whenever it meets a light source, repeating this many times per pixel and averaging the samples. A single unbranching path is traced each time, unlike Whitted-style or Cook-style ray tracing, which recursively samples branching paths. Because the samples are random, the image contains noise that falls as more samples are taken, and denoising techniques are often applied.