To keep things simple, we will map the troll in Figure 1 using a planar map created in Photoshop. I find it easiest to paint the maps if you have a template to use as a reference. To do this, simply render an image of the head from the front view. This image should be approximately as big as the character.
Figure 1 For this tutorial, we'll texture this head using a bitmap texture.
Getting Ready to Paint
Bring up the image in Photoshop or any other image-editing program. You are now ready to begin painting. If you want, you can paint directly on the image, but this will soon destroy your reference.
Figure 2 Bring up the image in Photoshop or any other image-editing program.
The better way is to create a new layer in Photoshop and paint on that. You can then adjust the opacity of the layer (arrow) to see how it matches with the reference.
Figure 3 The better way is to create a new layer in Photoshop and paint on that.
Painting Color Maps
Color is the most apparent of the maps that you will be creating. The color of the skin needs to fit the character and also look natural. A good starting point for skin textures are photographic maps of real skin. The type of map that you choose depends on the character. For this character, we're using a reptile-like texture, as shown in Figure 4. Using the clone stamp tool, paint the textures over the reference image to match the surface of the face.
Figure 4 This shows the final color map.
Painting Bump Maps
Bump maps are very important in creating a realistic surface. Skin is not a smooth surface; it has all sorts of imperfections. Characters have wrinkles, pores, blemishes, and so on. These sorts of details can be best created using a bump or a displacement map. Bump maps create the illusion that a surface is rough. A displacement map actually distorts the geometry of the underlying surface to get the same effect.
Both of these maps work by using a grayscale image that defines the intensity of the bump or displacement. Black pixels do not alter the surface at all, while white pixels give maximum effect.
The easiest way to create a slightly rough surface is to use a simple procedural map, such as noise. This will give the surface a rougher and more natural feel. Just adding noise, however, will give all parts of the surface equal roughness. Different areas of the face will need different bump mapsthe lips, for example, have a distinct texture that's different from the pores around the edges of the nose, which are different from the forehead. To get more accurate bumps, it's best to paint a map specifically for your model.
The procedure for painting a bump map is the same as for the color map, but simply done in grayscale. The rendered reference image of the character is opened in Photoshop, and the bump map is painted on a layer above the reference. When creating a bump map, try to make sure that you get a much contrast as possible. (See Figure 5.)
Figure 5 The final bump map.
Specularity defines how shiny a surface is at any given point. The face is shinier at different areasthe sides of the nose usually have more oil, so this part appears slicker. This is why many women powder their nose, to remove the shine. In any event, painting a specularity map enables you to define where the face is matte and where it is shiny.
Painting the specularity map is much like painting any other map type. The map is usually grayscale, much like the bump map. (See Figure 6.)
Figure 6 The final specularity map.