In this lesson we will continue our lightning overview of the world of surfacing, getting a handle on all the basic terms and concepts.

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Back to business.

In the last lesson (Lesson 12) we began our overview of SURFACING by introducing the idea of DIFFUSE COLOR, this being our most instinctive notion of the color of a physical object. It is the color that reveals itself under the lighting of the scene. We contrasted diffuse color with luminous color, which is color that is independent of the lighting, and is visible even if there is no lighting in the scene at all. We also contrasted SPECULAR REFLECTION, which creates highlights by reflecting the color of the light source rather than the color of the object.

We introduced the distinction between setting a single overall value for the diffuse color of an object and mapping the diffuse color with a TEXTURE MAP. We considered the two different approaches to texture mapping. One was to take an existing color bitmap image and wrap it around the object. The other approach was to allow the 3-D application itself to generate a procedural map for the object, using color and pattern input supplied by the user.

We stressed that the term "texture map" is confusing because it actually refers only to the diffuse color setting of the object, regardless of whether this diffuse color map creates the appearance of a surface texture. This is a good place to move forward because a very important aspect of surfacing is the creation of surface texture. The sense of 3-D realism depends enormously on texture or relief. Look at the wall in the room you are sitting in now. The small degree of texture across the surface is critical to the perception that this is a physical object and not an abstract geometric plane. Some objects, like an orange or a basketball, are almost defined by their textures. As we become accustomed to looking more carefully at the world around us, we begin to notice the subtleties of surface texture in a wide range of physical objects.

In a world of unlimited computer power, the surface textures of all our objects could be achieved by adding a huge amount of detail to the actual geometry of our models. A model of a basketball, for example, could be subdivided into tens of thousands of tiny polygons, and the all of the bumps in the surface could be worked into the geometric model. Or, to take an even move extreme example, a wall (which might otherwise be only a single flat polygon) could be subdivided into a massive number of points and polygons to model the roughness of the surface directly into the object geometry. Sometimes it is necessary to create such "high polygon count" models to create surface texture, as where mountains or detailed landforms are to be represented. But more often, we need to create the workable appearance of texture by using maps applied to the surface.

There are many overlapping approaches to the problem of creating texture effects. Let's take a look at them.