Phong Lighting Model (shadding)

How Used in OpenGL: Render Highlights/Specular separately and add to a non-specular rendering.

Phong Shading: Takes into account normal direction at a surface point in calculating the color.

More Details

One problem with Gouraud shading is that it does not really simulate a curved surface. On a real curved surface, the normal changes direction within a surface patch. The intensities that result may not correspond to linear interpolates of the vertex intensities. In particular, if there is a specular highlight somewhere in the middle of the face, that point will be bright while all the vertices will be dull. A more accurate shading model is Phong Shading. In Phong shading, the normals are linearly interpolated from the vertex normals. Then the lighting model is applied to every point using the computed normal.

© Lynne Grewe