Normal bump mapping is a way of adding high-resolution detail to low-polygon objects. It is especially useful for real-time display devices such as game engines, and it can also be used in rendered scenes and animations.
A normals map is a three-color map, unlike the grayscale maps used for regular bump mapping (see Bump Map). The red channel encodes the left-right axis of normal orientation, the green channel encodes the up-down axis of normal orientation, and the blue channel encodes vertical depth.
Basic Workflow
3ds Max provides a number of different ways to create and use normal bump mapping, but the most straightforward and simplest workflow involves these steps:
- Create a detailed, high-resolution model.
- Create a simpler, low-resolution model.
The low-resolution model should have the general shape and outlines of the high-resolution model, and typically it should be a bit smaller, so that projected detail in the high-res model will appear to be above its surface.
- Select the low-res model.
- Choose Rendering
Render to Texture. The Render To Texture dialog appears.
- On the Objects To Bake rollout, in the Projection Mapping group, click Pick.
3ds Max opens a selection dialog.
- Choose the high-res object, and then click Add.
3ds Max applies a Projection modifier to the low-res object.
- In the Projection Mapping group, turn on Enable. Note: At this stage, often you will click Options to display the Projection Options dialog, which has a variety of settings for how to generate the projection.
- On the Output rollout, add a NormalsMap element (see Baked Texture Elements). Assign Bump as its target map slot.
- In the Selected Elements Unique settings group, turn on Output Into Normal Bump.
- Click Render.
3ds Max renders the Normals map, which stores normals data from the high-res object. As for other kinds of texture baking, it creates a Shell material and applies that to the low-res object, with the Normals map assigned as the bump component.
Components of Normal Bump Mapping
In the 3ds Max interface, controls for normal bump maps appear in three locations:
- The Render To Texture dialog
Specifically, normal projection controls are found on the Objects To Bake rollout and the Output rollout.
- The Projection modifier
You can apply a Projection modifier yourself, or let Render To Texture do so automatically.
- The Normal Bump map type
Render To Texture creates this automatically if you turn on Output Into Normal Bump (step 9, above).
Viewing Normal Bump Maps
If you use a Nitrous driver (Nitrous Direct3D 11 is the default) or a Legacy Direct3D driver with DirectX 9 or later, you can view normal maps in any shaded viewport.
If you use a Legacy Direct3D driver with DirectX 8, you can view normal maps in viewports by using the Metal Bump shader.
If you use the OpenGL driver, in viewports normal bump maps do not appear to be three-dimensional. However, you can still render them and use normal mapping in renderings.
Normal Projection with Sub-Object Selections
You can associate different sub-object selections with different high-resolution geometry. See Reference Geometry Rollout (Projection Modifier).