3ds Max 2012 Bible - Kelly L. Murdock [366]
Tip
If the mental ray renderer is selected, then Ambient Occlusion is added to the list of available texture elements. The Ambient Occlusion option creates a map that re-creates effects created by limited light bounces resulting from surrounding objects. •
Baked Material and Automatic Mapping settings
The Baked Material and Automatic Mapping rollouts, shown in Figure 34.5, provide a way to keep the existing object material using the Shell material. The Clear Shell Materials button removes the Shell materials for the baked objects and restores their original materials.
FIGURE 34.5
The final two rollouts of the Render to Textures panel include settings for handling the baked material and how the texture is mapped.
In the Automatic Mapping rollout, you can set how the mapping is applied. If the Use Automatic Unwrap option in the Objects to Bake rollout is enabled, then the object to be baked has the Automatic Flatten UVs modifier applied. For this type, you can set the Threshold Angle (which is the difference between the normals of adjacent faces; if the angular value is greater than the Threshold Angle value, then a hard edge is created between the faces), the Spacing (which is the amount of space between different map pieces), and whether map pieces can be rotated and used to fill in holes of larger map pieces.
The size of the texture map depends on the size of the object, but you can set a Scale value for greater resolution and set Min and Max values to keep the maps within reason. By default, maps are saved to the /images directory, but you can select a different directory if you prefer. The Nearest Power of 2 option causes the map to be optimized for use in memory to a square pixel size that is a power of 2, such as 8 × 8, 16 × 16, 32 × 32, or 64 × 64.
Note
Most game engines require square texture maps because they are efficiently loaded into memory. Main characters can use texture maps that are 1024 × 1024 or even 2048 × 2048, but background characters and props usually only have textures maps that are 256 × 256 or 512 × 512, so clustering is important to get as much into the textures as you can. •
Tutorial: Baking the textures for a dog model
To practice baking textures, you'll bake a complete map of just the dog's head.
To bake a dog's head texture, follow these steps:
1. Open the Doberman.max file from the Chap 34 directory on the CD.
This file includes a dog model created by Viewpoint Datalabs.
2. Select Rendering⇒Render to Texture (or press the 0 key) to open the Render to Textures dialog box.
3. Select the dog's body object. In the Render to Textures dialog box, set the Threshold Angle to 75 in the Automatic Mapping rollout, and make sure that the Rendered Frame Window option in the General Settings rollout is set. In the Output rollout, click the Add button and double-click the CompleteMap option. Set the Map Size to 512, select the Diffuse Color option as the Target Map Slot, and click the Render button.
Figure 34.6 shows the resulting texture map. If you look in the Modify panel, you'll see that the Automatic Flatten UVs modifier has been applied to the object. If you look at the material applied to the object, you'll see that it consists of a Shell material.
FIGURE 34.6
A texture map created with the Render to Textures panel
Creating Normal Maps
Normal maps are becoming more common in games because they offer a way to increase the bump details of a model by mapping high-detail bump information onto a low-resolution model. Normal maps are created using the Render to Texture interface and applied to an object using the Normal Bump map type found in the Material Editor.
The Normal Bump map type is typically applied as a bump map in the Maps rollout and includes a separate