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Decoding Vertex Data for Graphics Rasterization

IP.com Disclosure Number: IPCOM000105310D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Kokoszka, D: AUTHOR [+2]

Abstract

In graphics rasterization, it is desirable to maintain 100% utilization of the cycle bandwidth when processing vertex data. Typically the vertex data is compressed into a parameter list and is input to the rasterizer serially. Disclosed is a circuit that achieves maximum utilization by decoding one parameter per cycle.

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Decoding Vertex Data for Graphics Rasterization

      In graphics rasterization, it is desirable to maintain 100%
utilization of the cycle bandwidth when processing vertex data.
Typically the vertex data is compressed into a parameter list and is
input to the rasterizer serially.  Disclosed is a circuit that
achieves maximum utilization by decoding one parameter per cycle.

      The circuit shown in the figure contains three components which
are the Vertex Definition Field 200, Priority Decoder 210, and a
Parameter Latch 220.  The Vertex Definition Field 200 defines the
number of parameters associated with the vertex.  If a bit is set to
binary '1', then that parameter is part of the vertex data.  The
Priority Decoder 210 examines the Vertex Definition Field 200,
determines the next parameter to process, and sets the correct
Parameter Latch 220.  There is a Parameter Latch 220 defined for each
vertex parameter.  The state of the Parameter Latches 220 indicates
which parameter is being processed.  If a latch is set to vinary '1',
the parameter associated with that latch is being processed or has
already been processed.

      To process the next parameter, the Priority Decoder 210 again
interrogates the Vertex Definition Field 200.  The decoder looks for
the leading zero.  Since the value of the Vertex Definition Field
changes each cycle, the first leading zero is the next parameter to
be processed.  As before, the decoder will set the appropriate
feed...