Patent ID: 6501482
Filing Date: 2002-12-31
Classification: G06T

Abstract:
A texture-map blender comprising:a texture-coordinate input receiving a u coordinate and a v coordinate of a texel in a texture coordinate space; a derivative input receiving derivatives representing rates of change of the u and v coordinates with respect to x and y screen coordinates; maximum derivative means, receiving the derivatives from the derivative input, for outputting a maximum derivative having a maximum absolute value; encoding means, receiving the maximum derivative, for finding a leading significant bit in the maximum derivative, a bit-position of the leading significant bit indicating a magnitude of the maximum derivative, the encoding means generating a level-of-detail LOD code indicating the magnitude of the maximum derivative; bit-selection means, receiving bits of the maximum derivative, for outputting fractional LOD bits that represent a fractional part of the maximum derivative wherein the LOD code represents an integer part of the maximum derivative; texture-memory means, receiving the u and v coordinates, for selecting a first LOD map identified by the LOD code and outputting four texels from the first LOD map, the texture-memory means containing a plurality of LOD maps representing a texture at different levels of detail; and blend-function enabling means, receiving the fractional LOD bits, for enabling blending of texels from two LOD maps when the fractional LOD bits are in a range near a LOD transition between LOD maps, and for enabling averaging the four texels from a single LOD map when the fractional LOD bits are not in the range near the LOD transition; whereby the fractional LOD bits determine when texels are blended from two LOD maps or from one LOD map.