GLSPECULAR

GL_SPECULAR is a material property used in OpenGL’s fixed-function lighting model to define the color of a surface’s specular reflection. It represents the mirror-like component of how light interacts with the material, contributing to the shiny highlight seen on illuminated objects.

In practice, GL_SPECULAR is specified per material with calls such as glMaterialfv, using the target face (for example GL_FRONT) and the pname GL_SPECULAR. The corresponding value is a four-component RGBA color that determines how strongly the material reflects specular light. The alpha component is typically ignored in lighting computations.

Specular reflection in the fixed-function pipeline is computed as part of the Phong (or Blinn-Phong) lighting model. The material’s GL_SPECULAR color is multiplied by the light’s specular color and intensity, and modulated by the material’s shininess, specified by GL_SHININESS. The shininess exponent controls the fall-off of the highlight: higher values produce smaller, sharper highlights, while lower values produce broader highlights. If the material’s specular color is zero, no specular highlight is produced, regardless of the light.

GL_SPECULAR interacts with other material properties such as GL_DIFFUSE, GL_AMBIENT, and GL_EMISSION to determine the final color and brightness of a surface under lighting. In modern OpenGL core profiles, the fixed-function pipeline is deprecated, and shading calculations are performed in shaders. GL_SPECULAR remains defined for compatibility contexts, but in core contexts, specular properties are typically supplied via shader uniforms instead of fixed-function calls.