Chapter 8 discusses creating terrain, the surface features of a land area in your game. This is a theory chapter. It is followed by application of the principles in chapter 9.
The author first discusses creating a terrain from a mesh and a manually created displacement map. He suggests that this might be done if the job is a small one. Examine the images on pages 196 and 197 to see the effect of displacement maps applied to terrain meshes. In each case, where the displacement map is black, the terrain is low. Where the displacement map is white, the terrain is high. Where the map is any tone in between, the terrain is proportionately high or low. Parts of the map with graduated tones provide graduated slopes on the terrain. Note the variety in the texture displayed in the terrain on page 197, resulting from the number of tones used in each portion of the displacement map. This is similar to topographic maps that use different colors to show different altitudes in the terrain.
On page 199, the text presents two meshes that have been deformed by maps. Note that the image at the top of the page seems much less realistic than the one at the bottom of the page. The author explains that the displacement map used on the upper image has an unintended harshness to it: the tones in the image jump abruptly in brightness, causing "artifacts" in the image. In this case, the artifacts appear as a series of abrupt changes in the height of the terrain. In the lower image, the transition from one height to another is much smoother, due to the more gradual change from one tone to another in the displacement map.
The author reminds us that the mesh itself can be deformed. You have used the 3DS Max soft and hard selection methods when sculpting the polygons of a mesh. It may be worth remembering that you can convert objects in 3DS Max to Editable Mesh or Editable Poly objects, but both types of objects are collectively referred to as meshes. The author tends to use the word "mesh" in this way. Whatever specific type of object we are working on, it can still be called a mesh.
The author explains that a terrain model can be less appealing if it has unintentional abrupt changes in it, and he presents two ways that this can occur.
In either of the cases above, the terrain will look less smooth and less believable. Consider the examples on pages 202 and 203. On page 202, we see that a high polygon count model is able to more accurately represent the variety of heights in a displacement map. On page 203, we see that the same mesh looks more real when a higher resolution map (more pixels) is applied to it.
The text turns to a series of features that may be found in different terrain editor programs.
The author turns to a discussion of software that might be used for terrain generation. He describes the problems he has encountered with them in general terms: most either produce output that is too detailed to use in a game, or they lack the functions that would make them useful tools. He recommends a product called L3DT, Large 3D Terrain Generator from Bundysoft.com. It is available in free and professional licensed versions. Mr. Ahearn explains that it has the best mix of features and usable output, in his opinion. You should read through the discussion of features of this program that form the end of this chapter.
The material in this chapter does not provide for useful exercises. I will assign a related activity that will further dress up your city scene.
Optional Exercise: Terrain Wizard