BlinnPhong

Blinn-Phong is a shading model used to approximate how light reflects from surfaces in computer graphics. It is a refinement of the Phong reflection model introduced by Jim Blinn in 1977, notable for replacing the reflection vector with a half-vector between the light and view directions.

In Blinn-Phong, the diffuse term follows Lambert's law with ambient light added, and the specular term is proportional to the dot product between the surface normal and the half-vector, raised to a shininess exponent: (N · H)^n, where H = normalize(L + V) is the half-vector and n is the shininess.

By avoiding explicit reflection calculations, Blinn-Phong is more efficient for real-time rendering and typically yields visually similar highlights to Phong, making it a staple in early OpenGL and Direct3D pipelines. It is commonly implemented as a combination of ambient, diffuse, and specular components, with per-material shininess and optional texture maps to control color and highlight size.

Limitations include its non-physically based nature and potential energy distribution inaccuracies compared to physically based rendering models. While capable of producing plausible highlights, it does not model the full Bidirectional Reflectance Distribution Function (BRDF) of real materials. Blinn-Phong can be extended with textures and more complex lighting setups, but modern rendering practices often prefer physically based rendering for accuracy and consistency across lighting conditions.