Precomputed Radiance Transfer (PRT) is a

computer graphics Computer graphics deals with generating images with the aid of computers. Today, computer graphics is a core technology in digital photography, film, video games, cell phone and computer displays, and many specialized applications. A great de ...

technique used to render a scene in real time with complex light interactions being precomputed to save time. Radiosity methods can be used to determine the diffuse lighting of the scene, however PRT offers a method to dynamically change the lighting environment. In essence, PRT computes the illumination of a point as a linear combination of incident irradiance. An efficient method must be used to encode this data, such as

spherical harmonic In mathematics and physical science, spherical harmonics are special functions defined on the surface of a sphere. They are often employed in solving partial differential equations in many scientific fields. Since the spherical harmonics form ...

s. When spherical harmonics are used to approximate the light transport function, only low-frequency effects can be handled with a reasonable number of parameters. Ren Ng extended this work to handle higher frequency shadows by replacing spherical harmonics with non-linear

wavelet A wavelet is a wave-like oscillation with an amplitude that begins at zero, increases or decreases, and then returns to zero one or more times. Wavelets are termed a "brief oscillation". A taxonomy of wavelets has been established, based on the num ...

s. Teemu Mäki-Patola gives a clear introduction to the topic based on the work of Peter-Pike Sloan et al. At SIGGRAPH 2005, a detailed course on PRT was given.

References

*Peter-Pike Sloan, Jan Kautz, and John Snyder. "Precomputed Radiance Transfer for

Real-time rendering Real-time computer graphics or real-time rendering is the sub-field of computer graphics focused on producing and analyzing images in real time. The term can refer to anything from rendering an application's graphical user interface ( GUI) to ...

in Dynamic, Low-Frequency Lighting Environments".

ACM Transactions on Graphics ''ACM Transactions on Graphics'' (TOG) is a bimonthly peer-reviewed scientific journal that covers the field of computer graphics. It was established in 1982 and is published by the Association for Computing Machinery. TOG publishes two special iss ...

, Proceedings of the 29th Annual Conference on Computer Graphics and Interactive Techniques (SIGGRAPH), pp. 527-536. New York, NY: ACM Press, 2002

*NG, R., RAMAMOORTHI, R., AND HANRAHAN, P. 2003. All-Frequency Shadows Using Non-Linear Wavelet Lighting Approximation. ACM Transactions on Graphics 22, 3, 376–381

{{compu-graphics-stub 3D computer graphics