Chapter 8: ZMapper 213 So the difference between a normal or bump map and a displace- ment map can be explained very simply. A displacement map changes the actual geometry to replicate your high-resolution model while using a much lower resolution base mesh, and normal and bump maps do not change the geometry at all. This is why the silhouette is so important. Sometimes you may find it easier to paint a simple bump map for very high-resolution detail and then roll this into your normal map. We'll discuss this in more detail a bit later, but I do feel the need to point out that a good set of UVs is very important for game related mod- els. Because texture space is at a premium in game engines, the artist must make the most of the texture space that is available. This is also why the majority of game friendly models use what are called "mirrored UVs," as this saves on texture space and thus memory, and helps the game to run faster. What Is a Surface Normal? A surface normal can be best explained as the direction a single polygon