Abstract: A texture value determining (TVD) circuit approximates non-homogenous 2nd order perspective texture mapping to provide texture for a polygon using linear interpolation and input parameters. The TVD circuit of the present invention includes a vertical walk subcircuit and an orthogonal walk subcircuit. The vertical walk subcircuit determines texture coordinates, u(a.sub.0,n) and v(a.sub.0,n) that represent the pixels along a vertical main slop of a triangle polygon. The orthogonal walk subcircuit determines texture coordinates, u(a.sub.m,n) and v(a.sub.m,n), for orthogonally walked polygon coordinate positions for which m>0. The orthogonally walked coordinate positions represent individual scan lines. The vertical walk subcircuit of the TVD circuit includes adders, latches, and accumulators. Each element of the vertical walk subcircuit receives a vertical main slope clock (n-clock) signal. An output of the vertical walk subsystem is computed based on the relationship,u(a.sub.0,n)=u(a.sub.0, n-1)+du.sub.

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.