The H-Test, a Method of High Speed Interpolative Shading

In computer graphics curved surfaces are commonly represented by a mesh of polygons. When these objects are rendered, the ‘visibility’ of the polygonal definition is diminished by using an interpolative shading algorithm. The two algorithms used for this are Phong shading (Phong 1975) and Gouraud shading (Gouraud 1971). Phong shading is capable of producing more realistic specular highlights, but is more expensive than Gouraud shading.