We can give the textures even more life by adding effects that will work on top of the base textures. Effects such as specularity and bump maps are included in most of today's games to add the appearance of shiny and rough surfaces.
Of course, you will need to check whether the game engine can handle specularity and bump maps. Secondly, you must verify that you have the texture space available for these effects. Each added effect will add another version of the texture page to the overall texture page count.
Bump maps are used to give objects the illusion of having even more detail. The bump map uses a grayscale height map that works with the surface normals of the model. This map tells us which areas on the texture need to be bumpy, and the normals tell the map what direction to work in. This technique does not add any geometry to the model, and the silhouette stays the same.
The specular map simply specifies which areas of the texture are shiny and which ones have a matte finish. It does this by producing a central hotspot and the halo surrounding it; together, they provide an illusion of reflected light.
In much the same way as an alpha map, bump and specular maps work off a grayscale image. White areas indicate higher bumps or shiny areas; darker areas create recessed areas or matte areas. As described earlier for alpha maps, the values for black and white may be inverted in some game engines; be sure to check this out.
Now let's explore briefly how we can implement bump and specular maps into our characters, while also seeing how to apply them in Maya.
Grae's Texture Effects
For a change, we will look at Grae first, because he will benefit more from these effects. His skin is quite bumpy, and in lots of areas the flesh is torn away to reveal muscle underneath. By applying a slight shine to this muscle, we can give the impression of moisture.
For the bump map, begin with a 50% gray background. This will allow you to add darker colors to act as recessed areas on the character, as well as lighter areas to create bumps.
Figure 9.44 shows the specular (top) and bump maps (bottom) we will be applying to Grae. You can find the completed maps on the CD in Project Files/09. Look for the files with _Bump or _Spec at the end of the filenames.
Figure 9.44. Grae's specular and bump maps
First we will apply the specular map. To apply a specular map, we first need to change the shader type. Lamberts are good for use with matte surfaces, but we cannot apply a specular map to this because it doesn't have the ability to be shiny. So we'll use a Blinn.
Repeat the foregoing procedure, applying the GraeMisc_Spec.tga file to the Grae_Misc material. Figure 9.46 shows Grae with the specular map applied. As you can see, only the areas you specified are shiny.
Figure 9.46. Grae with specular map applied (See page C9 for color version.)
Now let's add the bump map.
There we have itthe bump map is applied. Do these same steps for the Grae_Misc material.
With both the specular and bump maps applied, you can see in Figure 9.48 that the Grae model has dramatically improvedand without having to add any extra polygons.
Figure 9.48. Grae with both specular and bump maps applied (See page C9 for color version.)
Kila's Texture Effects
The bump and specular maps for Kila will create effects that are quite restrained.
Figure 9.49 shows the character with the bump and specular maps applied. You can see a subtle difference, but you and your team may want to decide whether this subtlety is worth adding four more texture pages. Whatever you decide, once the maps are created you can always decide to apply them at a later stage.
Figure 9.49. Kila with both specular and bump maps applied (See page C10 for color version.)