Image-Based Lighting 11 The earlier chapters in this book have described numerous properties and advan- tages of high dynamic range (HDR) imagery. A major advantage is that HDR pixel values can cover the full range of light in a scene and can be stored as cal- ibrated linear-response measurements of incident illumination. Earlier chapters have described how these images are useful for improved image processing, and for determining how a human observer might perceive a real-world scene, even if shown on a low dynamic range (LDR) display. This chapter describes how HDR images can be used as sources of illumination for computer-generated objects and scenes. Because HDR images record the full range of light arriving at a point in space, they contain information about the shape, color, and intensity of direct light sources, as well as the color and distribution of the indirect light from surfaces in the rest of the scene. Using suitable rendering