Importance

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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.main +(n-1)d.sup.2 u.sub.main for m=0, n>0 where du.sub.main and d.sup.2 u.sub.main are input parameters. The orthogonal walk subcircuit also includes adders, latches, and accumulators. The orthogonal walk subcircuit is clocked by an orthogonal walk (m-clock) signal as well as the n-clock signal. An output of the orthogonal walk subcircuit is computed based on the relationship, u(a.sub.m,n)=u(a.sub.m-1, n)+n(du.sub.ortho-ADD)+du.sub.ortho +(m-1)d.sup.2 u.sub.ortho for m>0 where du.sub.ortho -ADD and du.sub.ortho and d.sup.2 u.sub.ortho are input parameters.

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First Claim