Double Sided materials have just three parameters settings: Facing Material for the front material, Back Material for the back, and Translucency to determine the amount that the materials blend (from zero to 100 percent). Let’s create a double-sided material:

1.  In the Material Editor, create a Double Sided material by clicking the Type button and selecting Double Sided from the list of materials.

2.  Click the Facing Material button.

3.  Create a material of any type that you want to assign to the front faces.

4.  Click Go to Parent or use the Material/Map Browser to return to the top level of the material.

5.  Click the Back Material button and create a material for the back faces.

6.  Assign the material to an open object, such as a plane, a bowl, or a teapot without a lid.

7.  Render the scene.

Creating a Top/Bottom Material

Top/Bottom materials assign one material to all the faces whose normals point upward, and the other material to the rest of the faces whose normals point downward (the settings used to create Top/Bottom materials are defined in Table 9.6). In the demonstration in Figure 9.14, the top material uses a foliage map and the bottom map uses a stone map. (We mirrored and tiled the maps to make the final patterns.) At the boundary between up- and down-facing normals, you can blend the materials. You can also move the boundary up and down along the object’s Z axis. When you change the material from local to world coordinates, MAX determines the orientation of surface normals relative to the Z axis of the world coordinate system of the scene rather than the coordinate system of the object. The world-orientation of the material will then persist when the object is rotated.

FIGURE 9.14  A vase mapped with a Top/Bottom material

Let’s create a Top/Bottom material:

1.  In the Material Editor, create a Top/Bottom material by clicking the Type button and selecting Top/Bottom from the list of materials.

2.  Click the Top Material button.

3.  Create a material of any type that you want to assign to the top faces.

4.  Click Go to Parent or use the Material/Map Browser to return to the top level of the material.

5.  Click the Bottom Material button and create a material for the bottom faces.

6.  Position the boundary between the two materials.

7.  Set the amount that you want the two materials to blend at the boundary.

8.  Choose Local Coordinates if you want to keep the material aligned to the object’s Z axis.

9.  Assign the material to curved surface with faces that point both up and down.

10.  Render the scene.

Creating a Composite Material

Composite materials allow you to superimpose up to nine different materials in succession on top of a base material. The final outcome depends on the color and opacity of the component materials, the order in which they are laid down, and the method of compositing (see Figure 9.15). Figure 9.16 shows an example of an object given a Composite material. The base material contains a Cellular map. The first composite material contains a Checker map and the second uses Earth2.jpg, which is found in the Maps\space folder.

FIGURE 9.15  The Composite Basic Parameters rollout.

Figure 9.16  A vase mapped with a Composite material made up of three different materials

Under Composite Type, there are three options for compositing each material. The A button adds the color of the new material to what has been laid down previously, excluding areas of transparency. The S button subtracts the color of the new material from what is already present, excluding areas of transparency. For both the Additive and Subtractive options, values can range from zero to 200 percent. Above 100 percent the material becomes “overloaded” so that transparent areas of the material become opaque.

The M (mix) option blends the color and opacity of the current material with the previous state, just like the Blend material. Values range from zero to 100 percent. At zero, there is no blending and the current material has no effect. When Mix is set to 50 percent, they blend evenly. At 100 percent mixing, the color and opacity of the current material completely override the composite below it. (Note that the highest-numbered material is at the top of the composite pile, despite the rollout order.)

Each piece of the Basic Parameters rollout is explained in Table 9.7.

	TIP For complicated materials like the Composite material, it helps to have a bigger view. Double-clicking the material slot in the Material Editor magnifies the display.

Let’s create a composite material:

1.  In the Material Editor, create a Composite material by clicking the Type button and selecting Composite from the list of materials.

2.  Click the Base Material button.

3.  Create a material of any type for the base level material.

4.  Click Go to Parent or use the Material/Map Browser to return to the top level of the material.

5.  Create the first material that you want to composite with the base.

6.  Return to the top level.

7.  To the right of the first material, choose A for additive, S for subtractive, or M for mix. Remember that transparent areas won’t affect the base color unless you mix the material.

8.  Set the composite amount by dragging the spinner.

9.  Repeat steps 5 through 8 for as many new materials as you want to composite, to a maximum of nine.

10.  Assign the material to an object.

11.  Render the scene.

© 2000, Frol (selection, edition, publication)