Non-homogenous second order perspective texture mapping using linear

Abstract

In a computer system having a host processor, a peripheral graphics device, a display screen, and a memory, a non-homogenous second order perspective texture mapping process. Polygon coordinates, a.sub.m,n, defining a texture polygon, are received. Initial values are received for a set of parameters including u.sub.main, v.sub.main, dv.sub.ortho, dv.sub.main, du.sub.ortho, du.sub.main, d.sup.2 u.sub.ortho, d.sup.2 u.sub.main, d.sup.2 v.sub.ortho, d.sup.2 v.sub.main, du.sub.ortho-ADD, and dv.sub.ortho-ADD. The texture polygon includes span regions. A span value, j, is set to an initial value to designate an initial span region of the texture polygon in (m, n) polygon coordinate space. The total number of rows, n.sub.max, is determined for the current span region of the polygon. The total number of polygon coordinates, m.sub.max, in the current row, n, of the texture polygon is determined. An (x, y) display coordinate, corresponding to the current polygon coordinate, a.sub.m,n, is set by translating from (m, n) polygon space to (x, y) display coordinate space. Texture coordinates, u(a.sub.m,n) and v(a.sub.m,n), are determined, according to the present invention, for each polygon coordinate, a.sub.m,n, using linear interpolation based on a set of relationships that utilize the above parameters without using a repetitive divide operation. A display pixel of a color determined according to texture coordinates, u(a.sub.m,n) and v(a.sub.m,n), is rendered on a display screen at the determined (x, y) position.