MB86290A Datasheet, PDF (72/184 Pages) Fujitsu Component Limited. – Graphics Controller Hardware Specifications

6.5.4 Hidden Surface Management
This function compares the Z value of a new pixel to be rendered and the
existing Z value in the Z buffer. Display/not display is switched according to
the Z-compare mode setting. Define the Z-buffer access options in the
ZWRITEMASK mode. The Z-comparison type is determined by the Z compare
mode.
ZWRITEMASK
1 Compare Z values, no Z buffer overwrite
0 Compare Z values and overwrite result to Z buffer
Z Compare
mode
NEVER
ALWAYS
LESS
LEQUAL
EQUAL
GEQUAL
GREATER
NOTEQUAL
ID
Condition
000 Never draw
001 Always draw
010 Draw if pixel Z value < current Z buffer value
011 Draw if pixel Z value < current Z buffer value
100 Draw if pixel Z value = current Z buffer value
101 Draw if pixel Z value < current Z buffer value
110 Draw if pixel Z value > current Z buffer value
111 Draw if pixel Z value < current Z buffer value
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