glMaterial

glMaterial is an OpenGL API function used to specify material properties that interact with the fixed-function lighting model. Materials define how surfaces reflect light and contribute to the color and intensity of the final fragment when lighting is enabled.

Materials are described by several properties: ambient, diffuse, specular, emission, and shininess. Each property can be set for a specific face of a polygon, selected with the face parameter (GL_FRONT, GL_BACK, or GL_FRONT_AND_BACK). The properties are provided through either glMaterialfv for vector values (RGBA colors), glMaterialf for scalar values, or glMateriali for integer values. Common pname values include GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR, GL_EMISSION, GL_SHININESS, and, in older setups, GL_AMBIENT_AND_DIFFUSE or GL_COLOR_INDEX.

Ambient, diffuse, and specular define how light interacts with the material under the current lighting configuration. Emission adds light that the material itself appears to emit, independent of scene illumination. Shininess controls the specular highlight size, influencing the sharpness of shiny surfaces. These material properties are combined with the scene’s light sources and the active light model to determine the final color of each vertex and fragment.

Materials are effective only when GL_LIGHTING is enabled; otherwise glMaterial calls have no lighting impact. The interaction with glColorMaterial (if enabled) can also alter how color calls affect material properties.

In modern OpenGL, glMaterial and the fixed-function pipeline are deprecated in favor of shader-based approaches. Contemporary applications typically pass material-like data to shaders via uniform variables or textures, allowing full control over lighting calculations without relying on glMaterial.

Overall, glMaterial provides a straightforward, state-based mechanism to define surface reflectance in legacy OpenGL contexts, while its use has diminished in modern graphics programming.