A method and apparatus for dual pass adaptive tessellation includes a
vertex grouper tessellator operably coupled to receive primitive
information and an index list and a shader processing unit coupled to the
vertex grouper tessellator. During a first pass, the shader processing
unit receives primitive indices generated from the primitive information
and an auto-index value for each of the plurality of primitive indices.
The method and apparatus further includes a plurality of vertex shader
input staging registers operably coupled to the shader sequence, wherein
the plurality of vertex shader input staging registers are coupled to a
plurality of vertex shaders such that in response to a shader sequence
output, the vertex shaders generate tessellation factors. The
tessellation factors are provided to the vertex grouper tessellator such
that the vertex grouper tessellator generates a per-process vector
output, a per primitive output and a per packet output during a second
pass.