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Ray tracing (also called raytracing, ray-tracing or ray casting) is a technique for presenting three-dimensional (3D) images on a two-dimensional (2D) display by tracing a path of light through pixels on an image plane.
A ray tracing program mathematically identifies and reproduces the path that each light ray follows in reverse direction from the eye back to its point of origin. The path of each light ray consists of multiple straight-line components and nearly always involves reflection, refraction, or shadow effects from points within the scene. In animation, the position and orientation of the straight-line components of each ray constantly vary so each ray is represented by a mathematical equation that defines its path through space as a function of time. Rays are assigned a color based on the pigments the objects in the scene that the ray passes through and each pixel on the display corresponds to a ray.
Ray tracing was first developed in the 1960s by scientists at an organization known as Mathematical Applications Group. Ray tracing is used extensively in computer gaming and animation, television and DVD programming and movie production.