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Method and apparatus for projective texture mapping rendered from arbitrarily positioned and oriented light source

  • US 5,805,782 A
  • Filed: 01/23/1996
  • Issued: 09/08/1998
  • Est. Priority Date: 07/09/1993
  • Status: Expired due to Term
First Claim
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1. For a computer controlled display system for interactively displaying three dimensional graphical images, a method for obtaining pixel shading values directly from a texture map for pixels of a geometric primitive, said pixels having coordinates defined relative to an eye coordinate system, said geometric primitive having coordinates defined relative to a three dimensional world coordinate system, and said text map defined relative to a texture coordinate system, said method comprising the steps of:

  • a) identifying an origin point for a light coordinate system, said origin point being variably positioned, wherein said origin point of said light coordinate system is a source point for projecting said texture map onto said geometric primitive;

    b) determining coordinates in said light coordinate system of a point of said geometric primitive from coordinates of said point in said three dimensional world coordinate system;

    c) determining intermediate texture coordinates of said point in said texture coordinate system from coordinates of said point in said light coordinate system;

    d) determining coordinates of said point in said eye coordinate system from coordinates of said point in said three dimensional world coordinate system; and

    e) determining final texture coordinates of said point from a depth coordinate of said point'"'"'s coordinates in said eye coordinate system and from said point'"'"'s intermediate texture coordinates;

    f) wherein said final texture coordinates are used to obtain pixel shading values for shading a pixel on a screen of said display system, said pixel corresponding to said point of said geometric primitive; and

    g) wherein said final texture coordinates are used to obtain pixel shading values from said texture map.

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