Light ray tracing

The term light ray tracing, also called backward ray tracing, forward ray tracing or light tracing , describes an algorithm for image synthesis based on ray tracing .

It is a reverse of the normal ray tracing process. The rays are emitted by the light sources until they go into space or reach the observer's image. Like path tracing , light ray tracing is able to determine global lighting . However, the two methods work differently efficiently in different situations.

Light ray tracing has the disadvantage that of the many rays emitted by the light sources, most of them hit the void and less hit the image plane. As a result, a large number of beams are sent out unnecessarily. However, the method also has the advantage that certain lighting effects such as caustics can be simulated more easily than with normal ray tracing.

By photon mapping or path tracing extensions like Bidirectional path tracing it is possible to combine the advantages of simulations by the observer and by the light sources.

literature

• James Arvo: Backward Raytracing. SIGGRAPH 1986 course notes: “Developments in Ray Tracing” ( Online )
• Mark Watt: Light-Water Interaction using Backward Beam Tracing. In SIGGRAPH 1990 Proceedings. Pp. 377-385. ACM, New York 1990, ISBN 0-201-50933-4