TVP4020
Programmers Reference Manual
Graphics Programming
107
Note that if you are rendering to multiple buffers and have initialized the
start and increment values in the Color DDA unit, then any subsequent
Render command will cause the start values to be reloaded.
If subpixel correction has been enabled for a primitive, then any
correction required will be applied to the color components.
5.11.3
Flat Shading
In flat shading mode, a constant color is associated with each fragment.
This color is loaded into the ConstantColor register which has the format
shown in Fig. 5.36 above.
5.11.4
Registers
The main control register for the Color DDA unit is the ColorDDAMode
register:
0
8
16
24
31
Reserved
Shading Mode
Unit Enable
Figure 5.40
ColorDDAMode Register
The registers to set-up Gouraud shading in the Color DDA unit are:
Register
Data Field
Description
RStart
17 bit 2's comp fix pt
Red start value
dRdx
17 bit 2's comp fix pt
Red derivative per unit X
dRdyDom
17 bit 2's comp fix pt
Red derivative per unit Y, dominant
edge
GStart
17 bit 2's comp fix pt
Green start value
dGdx
17 bit 2's comp fix pt
Green derivative per unit X
dGdyDom
17 bit 2's comp fix pt
Green derivative per unit Y, dominant
edge
BStart
17 bit 2's comp fix pt
Blue start value
dBdx
17 bit 2's comp fix pt
Blue derivative per unit X
dBdyDom
17 bit 2's comp fix pt
Blue derivative per unit Y, dominant
edge
AStart
17 bit 2's comp fix pt
Alpha start value
Table 5.19
Color Interpolation Registers
Содержание TVP4020 PERMEDIA 2
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