Uses barycentric coordinate because between the polygonal Interpolation the system

摘要

PURPOSE: To smoothly make a shadow by calculating the centroid coordinates of a plane polygon in accordance with a prescribed formula at the time of interposing the plane polygon. CONSTITUTION: A plane polygon 24 is divided into, for example, triangles A1, A2 and A3 having three or more apexes. Triangles A1 to A3 have apexes P1, P2 and P3 respectively. A pixel C exists on a vector OP from a visual point O. Centroid coordinates b1, b2 and b3 of the polygon 24 are calculated in accordance with formulas where K1, K2 and K3 are the triple product of vectors OC, OP2. and 0P3, that of vectors OC, OP3 and OP1 and that of vectors OC, OP1 and OP3 respectively.