GLAMBIENTANDDIFFUSE

GL_AMBIENT_AND_DIFFUSE is an OpenGL color-material option used with the fixed-function lighting model to map the current color to both the ambient and diffuse material properties of the surfaces being drawn. When GL_COLOR_MATERIAL is enabled and GL_AMBIENT_AND_DIFFUSE is selected, calls to glColorMaterial or glColor* affect both ambient and diffuse reflectance for the specified faces, so the material’s ambient and diffuse terms share the same value.

In practice, this means the ambient term of the lighting equation, which represents a constant illumination, and the diffuse term, which follows Lambert’s cosine law with the surface normal, are computed using the same color. The resulting shading therefore responds to light direction similarly for both components, producing a uniform color across the lit surfaces, subject to the scene’s light sources and global ambient light.

Usage involves enabling GL_COLOR_MATERIAL, choosing the affected faces (such as GL_FRONT or GL_FRONT_AND_BACK), and selecting GL_AMBIENT_AND_DIFFUSE as the color-material mode. Then emitting colors with glColor* updates both ambient and diffuse material properties accordingly, for example setting glColor3f(1.0, 0.5, 0.0) would apply that color to both terms.

Limitations include its association with the fixed-function pipeline, which is deprecated in modern OpenGL core profiles. It offers less flexibility than setting ambient and diffuse properties separately or implementing material behavior in shaders. In contemporary practice, shader-based materials with explicit uniforms are preferred, though GL_AMBIENT_AND_DIFFUSE remains part of historical OpenGL and is encountered in legacy code and tutorials.