Design Nomenclature / Light & Optics
Ray tracing
Also called Whitted ray tracing, recursive ray tracing, RT
This entry has not been translated yet and is shown in English.
Historically, Whitted's 1980 method: trace one ray per pixel, recurse into the mirror and refraction directions, and fire shadow rays at point lights. It resolves specular transport and nothing else — no diffuse interreflection, and no soft shadows without extending it.
In practice
The GPU vendors' ray tracing means hardware-accelerated ray-triangle intersection, used for shadows, reflections, or GI. That is a machine, not the algorithm the words named for thirty years.
Not to be confused with
- Path tracingMonte Carlo integration of the rendering equation: follow a random walk from the camera, sampling one scattering direction per bounce, and average many such paths per pixel. Unbiased — noise falls as the square root of the sample count and the estimate converges on the correct answer.
- Global illuminationAny solution to light transport accounting for light that arrives after reflecting off other surfaces, not only direct from emitters. It is a category, not an algorithm — radiosity, photon mapping, path tracing, and irradiance caching all compute it, with different biases and different failure modes.
- RadiosityStrictly, a finite-element method that divides a scene into patches, computes form factors between them, and solves the resulting linear system for diffuse interreflection — view-independent, no speculars, and effectively unused since the 1990s. Loosely, and confusingly, the same word gets thrown at global illumination in general.