Bump and Specularity Maps


Bump and Specularity Maps

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.

NOTE

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.

1.

Open up the attributes for the Grae_Body material (Figure 9.45, left).

Figure 9.45. Change the Lambert shader to a Blinn.


2.

At the top of the shader's main attributes window, change Type from Lambert to Blinn. The layout should change to that seen in Figure 9.45, right. The name will also change, to blinn1; rename this back to Grae_Body.

By default, a Blinn material is shiny, so in effect you are telling Maya what levels of shininess each area of the texture should have.

3.

To apply a specular map, you follow much the same procedure as for applying the basic color map, except in this case we will be editing the Specular Color attribute in the Specular Shading section. Simply click the button to the right of the attribute and point the file window to the file called GraeBody_Spec.tga.

4.

To finish the application, adjust the Eccentricity and Specular Roll Off values to get the correct highlights.

Eccentricity controls the size of the highlights on the surface. The default value of 0.3 should work fine.

Specular Roll Off affects the intensity and sharpness of the highlight. Use 0.3 to get a good shine representing a wet surface.

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.

1.

Look at the Grae_Body materials attributes in the Attribute Editor, and you'll see the Bump Mapping attribute under the Common Material Attributes heading. This is where we assign our bump map.

Click the small button to the right of the Bump Mapping text box; this opens up the Create Render Node window. As you did when you applied the color texture, select File.

Now something different happens. Instead of going directly to the file window, you go to the actual bump nodes attributes (Figure 9.47).

Figure 9.47. The Bump Node attributes


2.

The only attribute we are interested in here is Bump Depth in the 2D Bump Attributes pane. Adjusting this will alter the emphasis your bump map has on the texture. A setting of 1 is usually far too severe, so set this to around 0.2.

3.

To help keep things tidy, rename this node to BodyBumpValue.

4.

Click the file1 tab at the top of the window; this brings you to the file's attributes. Select the bump map file called GraeBody_Bump.tga.

5.

Finally, rename file1 to BodyBump.

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.

  • Although Kila doesn't have any shiny areas, we can still make use of a specular map. The oils in our skin make it shine slightly when exposed to certain lighting conditions, so we can use the map to imitate this effect.

  • We can also employ a bump map to bring out some of the smaller details in the model. The creases in her clothing, or detail in her hair could benefit from this.

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.)