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Method for generating addresses to textured graphics primitives stored in rip maps

  • US 5,222,205 A
  • Filed: 03/16/1990
  • Issued: 06/22/1993
  • Est. Priority Date: 03/16/1990
  • Status: Expired due to Term
First Claim
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1. A method of addressing a rectangular texture map stored in a frame buffer and displaying a textured graphics primitive on a display device, comprising the steps of:

  • obtaining texture coordinate values S and T at the center of a pixel in screen space of said display device;

    calculating texture gradient values log2 Δ

    S and log2 Δ

    T as an approximation of an area in texture space covered by said pixel;

    calculating an S address to said frame buffer for said S texture coordinate value by;

    (a) truncating said S texture coordinate value to the size of a predetermined texture,(b) choosing one of a texture map for said predetermined texture and a down-sampled rectangular texture map corresponding to said predetermined texture for display on said display device,(c) using log2 Δ

    S, shifting predetermined logical values into said S texture coordinate value starting at an upper bit one greater than a most significant bit of said S texture coordinate value after truncation in said S address calculating step so as to obtain a modified value for said S texture coordinate value, and(d) adding said modified value for said S texture coordinate value to a coordinate origin value for said S and T coordinate values as an offset into said rectangular texture map so as to form said S address to said frame buffer;

    calculating a T address to said frame buffer for said T texture coordinate value by repeating said steps (a) through (d) using said T texture coordinate value in place of said S texture coordinate value and using log2 Δ

    T in place of log2 Δ

    S; and

    displaying a textured graphics primitive on said display device corresponding to a rectangular texture map stored in said frame buffer at said S and T addresses of said frame buffer.

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