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Beneath the Brush Options button is a Palette button that opens the Color Palette interface, shown in Figure 32.12. The Color Palette holds custom colors and lets you copy and paste colors between the different swatches. Collections of colors can be saved by right-clicking the Color Palette and selecting the Save As command. Color palettes are saved as Color Clipboard files with the .ccb extension.

FIGURE 32.12

The Color Palette can display colors as a list or as swatches.

The Paintbox also includes three subobject selection icons. These icons can be used to select certain Vertices, Faces, or Elements to be painted. This limits the painting to the selected subobjects only. You also can select to Ignore Backfacing and use Soft Selection.

The Blur brush button lets you blur colors across polygons using a brush that works just like the Paint and Erase brushes.

The Adjust Color dialog box lets you change all the painted colors applied to an object using HSV or RGB color sliders. The Preview option makes the color adjustment visible in the viewports if selected. Below the Adjust Color icon is the Blur Selected icon that blurs together all the vertex colors based on the designated Amount value.

Colors can be mixed between layers using the various blending modes. Clicking the New Layer button adds a new instance of the Vertex Paint modifier to the Modifier Stack; the Delete Layer button does the opposite. Click the Condense to a Single Layer button to merge all the consecutive Vertex Paint modifiers to a single instance using the selected blending mode.

Tutorial: Marking heart tension

As an example of using the Vertex Paint modifier, imagine a doctor who has a 3D model of the human heart. While discussing the results of the latest test with a patient, the doctor can color parts of the heart model to illustrate the various points.

To color on a human heart using the Vertex Paint modifier, follow these steps:

1. Open the Vertex paint on the heart.max file from the Chap 32 directory on the CD.

This file includes a heart mesh created by Viewpoint Datalabs.

2. Select a portion of the heart model, and choose Modifiers⇒Mesh Editing⇒Vertex Paint to apply the Vertex Paint modifier.

3. In the Paintbox that opens, choose the Vertex Color Display–Shaded button at the top of the Vertex Paint dialog box, select the red color, and click the Paint button. Then drag the mouse over the surface of the Perspective view.

Figure 32.13 shows the resulting color.

FIGURE 32.13

The Vertex Paint modifier can apply color to an object by assigning a color to its vertices.

The Assign Vertex Color utility

The Assign Vertex Color utility works a little differently. It converts any existing material colors to vertex colors. To use this utility, select the utility from the Utilities list that opens when you click the More button in the Utility panel, select an object, choose a Channel, choose a Light Model (Lighting + Diffuse, Lighting Only, or Diffuse Only), and click the Assign to Selected button.

Rendering Surface Maps

Max can be used to create some useful maps based on the geometry of the object. For example, a Cavity map is generated by looking at the concavity of the model. This appears as a grayscale map where the convex portions are white and the concave portions are black. Such a map can then be reused as a diffuse dirt submaterial map for showing those areas that are tight and indented. These tightly concave areas are the likely areas for non-specular highlights and for dirt to appear on old and weathered models.

Max can use the Render Surface Map feature to render several types of surface maps, including the following:

• Cavity map: The Cavity map creates a grayscale map that highlights convex areas in white and concave areas in black. The Contrast value defines the difference between black and white values.

• Density map: The Density map option creates a map that shows the areas where the vertices are closest together as white and farther apart as black.