NEC µPD72257 Preliminary User's Manual page 226

Chapter 8
Limiter1 Limiter2
Bandfilter Bandfilter
clamp
Combiner A
Figure 8-5
226
The final output is then used as an alpha value. Edge antialiasing can be done
with no additional effort with this hardware.
To calculate the decision value for the each possible pixel with a limiter the
bounding box of the object has to be calculated. After that the decision value for
the top left corner of the bounding box has to be calculated for each edge. Then
the increments for a step in x and a step in y direction have to be calculated. This
is done by the CPU in the driver.
With this information the Drawing Engine scans the whole bounding box and
calculates the decision value for every pixel incrementally. A block diagram of the
whole rasterization unit can be seen in figure "Simplified rendering pipeline setup"
in the chapter "Introduction".
Limiter3
clamp clamp
Combiner B
Combiner C
Combiner out
alpha output
Block diagram of the rasterization unit
Preliminary User's Manual S19203EE1V3UM00
Limiter4 Limiter5
clamp clamp
Drawing Engine
Limiter6
clamp
Combiner D