High Dynamic Range Imaging
Short for High Dynamic Range Imaging, HDRI is an imaging technique that allows for a greater dynamic range of exposure than would be obtained through any normal imaging process. HDRI is now more commonly used for real photograph scenes where, for example, a large range of exposures would be found between sunlight and shadows. However, it was initially developed for use with computer-generated graphics and images. HDRI, also called HDR (High Dynamic Range) is a feature commonly found in high-end graphics and imaging software.
See also "An Introduction to High Dynamic Range Imaging" on Graphics.com.