OpenGL Programming Guide

Chapter 13Now That You Know

Texture-Mapping Applications

Texture mapping is quite powerful, and it can be used in some interesting ways. Here are a few advanced applications of texture mapping:

• Antialiased text - Define a texture map for each character at a relatively high resolution, and then map them onto smaller areas using the filtering provided by texturing. This also makes text appear correctly on surfaces that aren't aligned with the screen, but are tilted and have some perspective distortion.
  
  

• Antialiased lines - These can be done like antialiased text: Make the line in the texture several pixels wide, and use the texture filtering to antialias the lines.
  
  

• Image scaling and rotation - If you put an image into a texture map and use that texture to map onto a polygon, rotating and scaling the polygon effectively rotates and scales the image.
  
  

• Image warping - As in the preceding example, store the image as a texture map, but map it to some spline-defined surface (use evaluators). As you warp the surface, the image follows the warping.
  
  

• Projecting images - Put the image in a texture map, and project it as a spotlight, creating a slide projector effect. See "The q Coordinate" for more information about how to model a spotlight using textures.

See Chapter 3 for information about rotating and scaling, Chapter 9 for more information about creating textures, and Chapter 11 for details on evaluators.

OpenGL Programming Guide