Using Dynamics Properties

Dynamics is a utility in MAX that detects and emulates real-world collisions. The Dynamics Properties rollout (in the Raytrace material; see Figure 9.9 and Table 9.4) allows you to determine the bounce and friction coefficients of an object based on its material assignment. The Dynamics Utility uses the values that you set in order to calculate collisions. It can also override these settings with new ones that you set in the Utility. So why have them in the Material Editor at all?

Because the Dynamics Properties rollout appears at the top level of Standard and Raytrace materials, you can set the dynamics properties of objects at the sub-object level using Standard and Raytrace materials as part of a Multi/Sub-Object material tree. This is something you cannot do from within the Dynamics Utility, so this rollout provides a level of refinement in which different parts of an object have different levels of elasticity and friction.

FIGURE 9.9  The Dynamics Properties rollout

Creating Matte/Shadow Materials

The Matte/Shadow material turns an object to which it is applied into a matte object. A matte object is an invisible object that obscures scene geometry but reveals the environment map behind. By casting and receiving shadows, matte objects can simulate the presence of shadows in a background, furthering the illusion that scene geometry is embedded within it. Matte/Shadow materials provide settings for rendering alpha channels, atmospherics, shadows and reflections (see Figure 9.10 and Table 9.5).

FIGURE 9.10  The Basic Parameters rollout for Matte/Shadow materials

Creating Shadows on a Background Using a Matte Object

Let’s use a matte object to create shadows on a background:

1.  Create a camera and turn on the Horizon.

2.  Assign an environment map to the background (see Figure 9.11).

FIGURE 9.11  The teapot’s shadow was created using a Matte/Shadow material, Chromblu.jpg, that comes with MAX in the Maps\ref_maps folder.

3.  Use the Views menu to display the environment map in the background of the camera view.

4.  Align the horizon of the camera to the horizon of the background image.

5.  Create a plane in the camera view that matches the ground in the background image.

6.  Create an object on the plane.

7.  Create a directional light and point it in the same direction as the light in the background image.

8.  Turn on the light’s shadow and widen the falloff so that the object casts a shadow.

9.  Refine the alignment of the light so that the object’s shadow matches the background shadows.

10.  In the Material Editor, create a Matte/Shadow material by clicking the Type button and selecting Matte/Shadow from the list of materials.

11.  In the Matte/Shadow Basic Parameters rollout, uncheck Opaque Alpha. Then check Receive Shadows and Affect Alpha. Set Shadow Brightness to 0.1.

12.  Assign the material to the plane object.

13.  Render the scene.

	TIP To see if the matte shadow has been rendered to the alpha channel, click Display Alpha Channel in the Virtual Frame Buffer (see Figure 9.12).

FIGURE 9.12  Rendering a shadow to the alpha channel

	TIP To reflect the environment in a matte object, use a Reflect/Refract map or a Flat Mirror map for the reflection map.

Building Compound Materials

Compound materials, like compound objects, combine two or more materials into one. You have already seen how this works with Multi/Sub-Object materials. Of the five other types of compound materials, only Morpher materials have the potential complexity of numerous material combinations. The other four materials, Double Sided, Top/Bottom, Composite, and Shellac, combine only two materials to obtain the final compound.

Creating a Double Sided Material

All faces have two sides: a front side, which is the side that the surface normal is on, and a back side, which is on the inside, or back, of an object. By default, only the front side of a face is rendered. This saves rendering time while giving the outside of the object its visible form. To see the inside of an object, or check for flipped faces, you need to be able to render both sides.

There are a few different ways to render the front and back faces of an object. The simplest way is to check Force 2-Sided option of the Render Scene rollout. This causes the scanline renderer to apply the same color to the front and back faces of all objects in the scene. Checking 2-Sided in the Shader rollout of an object’s material does the same thing, without the overhead of rendering both sides of every object.

Double Sided materials open up the possibility of using different materials on each side of an object. These materials can have their own material tree of any size, and they can be blended together as if you are seeing through a translucent wall from one side to the other. In the example in Figure 9.13, the front material uses a tiled and mirrored map of the sky. The back material uses a Noise map.

FIGURE 9.13  A teapot mapped with a Double Sided material

© 2000, Frol (selection, edition, publication)