Four Lights Demo
The demo shows a scene that is illuminated by four light sources, as well as by a dim global ambient light. There is a "viewpoint" light, which is a white light shining into the scene from the direction of the viewer. There are three colored positional lights, with a small sphere at the position of each light. The checkboxes allow you to turn the lights off and on. You can control whether the base is displayed. You can turn on an animation that makes the colored lights fly in circles around the teapot. And you can rotate the scene as a whole using your mouse.
Some things to do: Turn off all of the lights except one, and note the effect of that light on the teapot. (Maybe turn off the base so it doesn't distract you.) For the colored lights, be sure to use animation so that you can see how the colors on the teapot change. Try it with only two colored lights turned on, and see how their colors combine. Note that when one a colored light is turned on, it adds some of its color to the ambient light; to see the effect look at the bottom of the teapot, with just one light turned on (and display of the base turned off).
Note that when the only light source is a single colored light, part of the base is black; this is because, for example, a part of a surface that contains no red will not reflect any red light.
You might also note that the teapot does not cast shadoes on the base. OpenGL does not support shadows, except with a lot of extra work.
The base has a material that changes colors around the edge of the cylinder. This is meant as a demonstration of using different material colors at different vertices of the same primitive. It also uses GL_COLOR_MATERIAL so that the material colors can be set by calling glColor3fv instead of glMaterialfv.
