Appeal No. 2005-1995
Application 09/133,741
lines 46-47). Assume there are two buffers, Buffer 1 and
Buffer 2. The output list of vertices from the Initial State in
Buffer 1 is copied to the input list in (initially cleared)
Buffer 2; Buffer 1 is cleared; the clipping routine generates
vertices in the output list of Buffer 2; the output list from
Buffer 2 is copied to the input list is Buffer 1; Buffer 2 is
cleared; and the process repeats. It is possible to copy the
output list to the input list by overwriting the input list, but
this also does not act like a circular buffer.
Sutherland states (page 735, first col.):
Perhaps the most important applications of
micropipelines will involve operations in which the vector
length changes. One such example is the clipping operation
widely used in computer graphics. The clipping operation
removes the parts of a set of objects that lie outside a
reference window. Clipping may result in an increase or
decrease in the number of objects in the set. Because whole
objects may be removed, there may be less output than input,
but because connected edges may also be broken into multiple
pieces, there may also be more output than input. Such a
clipping device with very simple interface characteristics
can be built using the micropipeline framework.
Although appellant states that "[t]his passage certainly does
suggest the use of circular buffers in connection with clipping
operations, but does not suggest COMBINING two conventional
circular buffers into one" (Br12), we find no mention of circular
buffers here. However, Sutherland earlier stated that "one can
build a ring-buffer FIFO whose interface characteristics are the
same as those of the micropipelined FIFOs of Figure 15 or Figure
16" (page 732), and this suggests that micropipelines, linear or
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