VT8601 Apollo ProMedia
Revision 1.3 September 8, 1999
-131
3D Graphics Engine Registers
7HFKQRORJLHV ,QF
:H&
:H&RRQQHFW
QQHFW
GEbase + 7C – Alpha ........................................................RW
31-16 Reserved
........................................ always reads 0
15-8 Source Constant Alpha
7-0
Destination Constant Alpha
GEbase + 84 – Bit Mask....................................................RW
31-0 Bit Mask
One bits indicate that the corresponding color bit will
not be written to the frame buffer.
GEbase + 80 – Alpha Function ........................................ RW
31-24 Reserved
........................................ always reads 0
23
Alpha Write
0
Disable................................................... default
1
Enable. Draw each pixel with a blended alpha
value if alpha blending is enabled. Otherwise
draw with source alpha (the upper byte of the
Foreground Color register if not available).
This bit should be set in 8-bit and 16-bit color modes.
22
Constant Source Alpha
0
Disable .................................................. default
1Enable
21
Constant Destination Alpha
0
Disable .................................................. default
1Enable
20
Result Alpha
0
The result of blending ........................... default
1
Source alpha
19-16 Alpha Test Function
0000 Never accept the pixel
0001 Accept if alpha < reference alpha
0010 Accept if alpha == reference alpha
0011 Accept if alpha <= reference alpha
0100 Accept if alpha > reference alpha
0101 Accept if alpha != reference alpha
0110 Accept if alpha >= reference alpha
0111 Always accept the pixel
1xxx -reserved-
15-8 Reference Alpha Value
7-4
Destination Blending Factor
0000 (0,0,0,0)
0001 (1,1,1,1)
0010 (RS,GS,BS,AS)
0011 (1,1,1,1) - (RS,GS,BS,AS)
0100 (AS,AS,AS,AS)
0101 (1,1,1,1) – (AS,AS,AS,AS)
0110 (AD,AD,AD,AD)
0111 (1,1,1,1) – (AD,AD,AD,AD)
1xxx -reserved-
3-0
Source Blending Factor
0000 (0,0,0,0)
0001 (1,1,1,1)
001x -reserved-
0100 (AS,AS,AS,AS)
0101 (1,1,1,1) – (AS,AS,AS,AS)
0110 (AD,AD,AD,AD)
0111 (1,1,1,1) – (AD,AD,AD,AD)
1000 (RD,GD,BD,AD)
1001 (1,1,1,1) - (RD,GD,BD,AD)
1010 (F,F,F,1); F = min (AS, 1-AD)
1011 -reserved-
11xx -reserved-
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
