OpenGL Programming Guide

Chapter 6Lighting

Selecting a Lighting Model

Global Ambient Light

As discussed earlier, each light source can contribute ambient light to a scene. In addition, there can be other ambient light that's not from any particular source. To specify the RGBA intensity of such global ambient light, use the GL_LIGHT_MODEL_AMBIENT parameter as follows:

GLfloat lmodel_ambient[] = { 0.2, 0.2, 0.2, 1.0 };
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, lmodel_ambient);

In this example, the values used for lmodel_ambient are the default values for GL_LIGHT_MODEL_AMBIENT. Since these numbers yield a small amount of white ambient light, even if you don't add a specific light source to your scene, you can still see the objects in the scene. Figure J-18 shows the effect of different amounts of global ambient light.

OpenGL Programming Guide