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Support SIMD8 instructions for vertex processing and SIMD16 instructions for pixel
processing.
2.4.1.2
3D Pipeline
2.4.1.2.1
Vertex Fetch (VF) Stage
The VF stage executes 3DPRIMITIVE commands. Some enhancements have been
included to better support legacy D3D APIs as well as SGI OpenGL*.
2.4.1.2.2
Vertex Shader (VS) Stage
The VS stage performs shading of vertices output by the VF function. The VS unit
produces an output vertex reference for every input vertex reference received from the
VF unit, in the order received.
2.4.1.2.3
Geometry Shader (GS) Stage
The GS stage receives inputs from the VS stage. Compiled application-provided GS
programs, specifying an algorithm to convert the vertices of an input object into some
output primitives. For example, a GS shader may convert lines of a line strip into
polygons representing a corresponding segment of a blade of grass centered on the
line. Or it could use adjacency information to detect silhouette edges of triangles and
output polygons extruding out from the edges.
2.4.1.2.4
Clip Stage
The Clip stage performs general processing on incoming 3D objects. However, it also
includes specialized logic to perform a Clip Test function on incoming objects. The Clip
Test optimizes generalized 3D Clipping. The Clip unit examines the position of incoming
vertices, and accepts/rejects 3D objects based on its Clip algorithm.
2.4.1.2.5
Strips and Fans (SF) Stage
The SF stage performs setup operations required to rasterize 3D objects. The outputs
from the SF stage to the Windower stage contain implementation-specific information
required for the rasterization of objects and also supports clipping of primitives to some
extent.
2.4.1.2.6
Windower/IZ (WIZ) Stage
The WIZ unit performs an early depth test, which removes failing pixels and eliminates
unnecessary processing overhead.
The Windower uses the parameters provided by the SF unit in the object-specific
rasterization algorithms. The WIZ unit rasterizes objects into the corresponding set of
pixels. The Windower is also capable of performing dithering, whereby the illusion of a
higher resolution when using low-bpp channels in color buffers is possible. Color
dithering diffuses the sharp color bands seen on smooth-shaded objects.
30
Interfaces
Datasheet
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