ATTRIBUTE INTERPOLATION IN 3D GRAPHICS

An image processing method and apparatus are described for rendering two dimensional pixel images composed of triangular image primitives. Prior to their projection into the image plane, each triangle is parameterised with a respective two-dimensional coordinate system with the coordinate axes (s,t) concurrent with respective edges of the triangle and the origin (0,0) coincident with the vertex (V.0) between those edges. A generalised interpolation function, applied in terms of the parameterising (s,t) coordinate system, determines parameter values at positions (P) within the triangle in terms of the two-dimensional coordinate system. These parameter values determine contributions from stored values for one or more attributes, such as surface normal or texturing, stored for each vertex, to give attribute values at each pixel. In a final stage, the per pixel attribute values from all triangles are used to jointly determine an output color for each pixel.