This document discusses how to work with heightmaps, which are raster images used to store elevation data for 3D terrain modeling. Each pixel in a heightmap represents a height value. Heightmaps can be used for bump mapping, displacement mapping, and terrain modeling by converting the heightmap data into a 3D mesh. Heightmaps store elevation as grayscale values and can be created manually or algorithmically. They are commonly used in terrain software and video games to efficiently store terrain height data compared to polygonal meshes.