TIP You can use the Extra Light setting to simulate radiosity (the effect of light reflected from one surface coloring another). Just set the color swatch to match the color of a nearby object.

FIGURE 9.4  Extended Parameters for the Raytrace material provide advanced surface controls for lighting, reflection, and translucency.

	TIP Fluorescence shifts the surface color toward a color you select and then illuminates it with white light. Setting the Fluorescence Bias parameter to 1.0 and using a fully saturated color results in an intense, “black light” effect.

Creating a Translucent Surface

In nature, translucent objects partially transmit light, creating an opaque or semi-transparent surface that displays contrasts of light and shadow. In MAX, translucent objects (like the one in Figure 9.5) simply receive shadows from the back of a surface and project them onto the front.

FIGURE 9.5  A translucent lamp with a moth casting shadows through its wall

To create a translucent surface:

1.  Create a open object, such as a plane, a vase, or a lamp shade.

2.  Set up an object and a light so that the new object casts a shadow on the inside or back of the open object.

3.  Create a 2-Sided Raytrace material.

4.  In the Raytrace Basic Parameters rollout, set the Transparency to about 35.

5.  In the Raytrace Extended Parameters rollout, set the Translucency swatch to light gray.

6.  Assign the Raytrace material to the open object.

7.  Render the scene.

	NOTE The Translucency parameter affects only shadow mapping and light distribution. It does not cause the surface to become semi-transparent.

Applying Maps to a Raytrace Material

You can apply maps to all of the basic and extended parameters mentioned previously, including Ambient. In addition, the Maps rollout (see Figure 9.6) allows you to apply a displacement map to your material. Displacement mapping alters the geometry of the object to which it is applied according to the grayscale values of a bitmap or a procedural map (this is demonstrated in Figure 9.7). Dark values on the map indent the surface; light values raise it in relief. Compare this to bump mapping, in which surface texture is simulated by shading, but surface geometry remains unchanged.

To displace anything other than an editable mesh or NURBS surface, you must first apply a Displace Approximation modifier to the object to make the surface displaceable. Displace Approximation works with any surface that can be converted to an editable mesh. Once the surface has been prepared, you simply apply the Raytrace material with the displacement map. The degree of displacement of the surface is controlled by the Amount spinner in the Maps rollout.

Be forewarned that displacement mapping creates a high overhead in terms of geometry. If you can get by with bump mapping, that will save you a lot of time; but if you truly need to displace a surface, this is a quick and efficient way to model details.

FIGURE 9.6  You can apply many maps to your Raytrace material’s parameters.

Figure 9.7  Displacement mapping (left) alters geometric structure. Compare this to the bump-mapped shadows that simulate geometry (right).

Setting Raytracer Controls

Raytracer controls govern how the raytrace engine renders materials (see Table 9.3 and Figure 9.8). You can, and should, optimize performance by turning off unnecessary reflections or refractions, and by excluding objects. For greater accuracy you can increase the number of iterations, or “recursion depth,” that the raytracer performs. Additional controls include settings for anti-aliasing, blurring, and falloff.

FIGURE 9.8  The Raytracer Controls rollout controls the raytrace rendering engine.

© 2000, Frol (selection, edition, publication)