Projection Modifier

The Projection modifier is used primarily to manage objects for producing normal bump maps. You apply it to the low-resolution object, and then pick a high-resolution object as the source for the projected normals. When you use the Render To Texture dialog to set up projection, Render To Texture applies the Projection modifier to the low-resolution object automatically. You can also explicitly apply the Projection modifier to set up the projection before you use Render To Texture.

• Select an object. > Modify panel > Modifier List > Object-Space Modifiers > Projection
• Standard menu: Select an object. > Modifiers menu > UV Coordinates > Projection
• Enhanced menu: Select an object. > Modifiers menu > UVs, Maps and Materials > Projection

Note: The low-resolution object requires UV coordinates, but the high-resolution source object does not need to have them. When the normals map is rendered, you can choose to have Render To Texture apply an “Automatic Flatten UVs” (Unwrap UVW) modifier to the top of the low-res object's stack; or you can use existing mapping, if such exists.

You can apply more than one instance of the Projection modifier to the same object, and you can instance it across multiple objects.

The Projection modifier is a topology-dependent modifier, so when you select an item in the stack that is lower than the Projection modifier, you see a warning dialog that asks if you want to proceed. (The same is true of the Automatic Flatten UVs modifier.)

Projection and Sub-Object Selections

You can match geometry to sub-object selections. There are two ways to do so: matching material IDs, or matching named selections of sub-object geometry.

Matching Material IDs

Here is a sample workflow for using material IDs to match portions of the low-res object to different high-res objects:

1. At the level of the low-res object itself, assign differing material IDs to different face selections.

   To do so, the low-res object must be a surface model; that is, an editable mesh, editable poly, editable patch, or NURBS surface. Use the Surface Properties rollout to change the material ID of sub-object selections.

2. For the high-res target objects, assign corresponding material IDs.

   An easy way to do this is to apply the Material modifier.

3. In the Resolve Hit group of the Projection Options dialog, turn on Hit Only Matching Material ID.
4. Render to texture.

   The texture for faces of the low-res object receive texture element information only from the source object that had the corresponding material ID.

Matching Selected Geometry

Here is a sample workflow for using sub-object selections to match portions of the low-res object to different high-res objects.

1. In the Projection modifier, go to the Face or Element sub-object level.

   See Selection Rollout (Projection Modifier).

2. Make a sub-object selection, then on the Reference Geometry rollout, enter a descriptive name in the Name field.
3. Click (Add) or press Enter.

   The name of the sub-object selection set is added to the list.

4. Click in the list to highlight the selection-set name, click Pick or Pick List, and then select the high-res source object to associate with the sub-object selection.
5. Repeat steps 2 through 4 to associate different sub-object selections with different source objects.
6. Choose Rendering Render To Texture.

   The Render To Texture dialog appears.

7. In the Projection group of the Objects To Bake rollout, turn off Object Level and turn on Sub-Object Levels.
8. Click Render.

   Render To Texture renders a separate texture for each of the named sub-object selections contained in the Projection modifier.