Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Patent
1997-08-27
2000-05-02
Powell, Mark R.
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
345434, G06F 1500
Patent
active
060578483
ABSTRACT:
A high order surface patch rendering system. A patch is rendered by subdividing a patch until the subpatches are sufficiently flat that they can be approximated by a quadrilateral, which can then be split diagonally and written to a rasterizer in the form of two triangles. In one embodiment, the patch rendering system receives rational coordinates (X,Y,Z,W) and attribute coordinates (color, opacity, texture) of control points of the Bezier surface patch. The patch rendering system divides and subdivides the surface patch by operating on the surface patch control points to produce subpatch control points. The rational coordinates of the control points are converted to spatial coordinates, and if the current subpatch is determined to be flat, the spatial coordinates and attributes of the subpatch corner points are provided to an output buffer in the form of triangle vertices with associated attributes. The patch rendering system which includes a patch tessellation device for converting a Bezier surface patch having a set of control points to a plurality of triangles for display. The patch tessellation device comprises a patch buffer, a patch division unit, a homogeneous coordinate unit, and a corner unit. The patch buffer is configured to receive and store rational coordinates of current control points of a current surface patch. The patch division unit is coupled to receive the rational coordinates of the current control points from the patch buffer and configured to calculate rational coordinates of new control points for a new surface patch. The homogeneous coordinate unit is coupled to receive the rational coordinates of the new control points and configured to convert the rational coordinates of the new control points to spatial coordinates of the new control points. The corner unit is coupled to the homogeneous coordinate unit to receive the spatial coordinates of new control points which correspond to corner points of the new surface patch, and configured to provide the spatial coordinates for corner points of the new surface patch as triangle vertices to an output buffer if the new surface patch is classified as flat. In addition to the coordinates, the patch tessellation device may also operate on Bezier patches specifying attributes of the surface patches.
REFERENCES:
patent: 5377320 (1994-12-01), Abi-Ezzi et al.
Harrison Chante
Kivlin B. Noel
LSI Logic Corporation
Powell Mark R.
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