Custom Materials for 3DS MAX

pt.3

So far I've talked about the importance of diffuse maps and bump maps in designing materials. Diffuse maps provide color to the material, bump maps supply texture; next we need to determine how light interacts with materials.

Light and Perception

Light is necessary for sight, and the way in which light interacts with the objects around us provides us with an incredible amount of information. The interaction of light with objects allows our brains to understand round from angular, smooth from rough; it helps us identify size, shape, and material. That information in turn allows us to make inferences about the weight of an object, whether it is safe to touch or approach, and many other things. For most people the way light interacts with the elements of our environment and is then translated by the visual centers of our brains is our primary means of gathering information about our environment. The way we interpret light is often key to how we react to the physical world; that is why things like faux finishes on furniture are successful. Think of making materials in MAX as painting faux finishes that use light (as color, definition of texture, reflectivity, and transparency) to fool you brain into "knowing" what a material is. The two most basic maps MAX uses for defining light/material interactions are the specular maps and the reflect map.

Specular Color

The specular attributes of a material are controlled in two ways in MAX. First there is specular color, then there are the specular highlights. Specular settings relate to the light that is reflected off an object, it's color and intensity. In the Materials Browser the controls for Ambient, Diffuse, and Specular settings are all located in the Blinn Basic Parameters rollout. The controls for Specular Highlights are located below the Specular settings controls.

The specular color controls the color of the highlight on a material. The color of the highlight on an object actually supplies a lot of information about the material. If the highlight on an object reflects more of the color of the light source we assume the surface of the object is smoother and harder. If the specular color is closer to the color of the object we assume the surface is more textured, more porous, possibly softer.

The sphere on the left appears to be made of hard plastic or glass while the sphere on the right looks more like hard rubber or painted wood. The only difference between the two materials is the specular color.

The Specular Highlights controls affect the strength with which the specular color is reflected. In simpler terms it gives you added control over a material's shininess.

The material on the two spheres above have identical specular colors; however, as you can see by their settings they have different specular levels. This creates an effect almost the same as the one seen above where the levels are the same but the colors are different. The spheres above don't necessarily seem to be made of different materials. It looks instead like the sphere on the left has been polished.

What does any of this mean to a material designer? How do you make use of this information? In the illustration below the models on the left and right are nearly identical. The bitmap applied to the stone surface is identical; the lighting applied to each set of objects is identical. The only differences between the objects on the left and the objects on the right are the specular settings.

The brass candleholder and the stone tabletop on the left look as though they have been polished. The specular highlights on the materials on the left were set to more closely match the color of the lights in the scene, and the intensity of those highlights was turned up. On the right the specular colors were matched to the basic colors of the material, and the intensity was turned down.

I gave a lighter specular color to the brass material and the stone material on the left so that they appear to reflect more of the light. Then I used the Specular Highlight controls to fine tune the shininess of those materials. All the other material parameters are the same on the right and left hand models. Specular settings can make a big difference in how your materials are interpreted.

This would be a good place to take a break. Go stretch your legs, give your eyes a break, get a snack...When you come back move on to page 2 for some information on Reflection Mapping.