TVP4020
Programmers Reference Manual
Graphics Programming
115
5.12.7
Registers
The TextureColorMode register is used to enable and disable texturing
(qualified by the texture application bit in the Render command register).
The KsDDA and KdDDA bits enable the internal DDAs and should be
set for modulate or highlight Ramp texture application modes. The
Texture Type field differentiates between Ramp and RGB application
modes. Combinations of decal, modulate and highlight are supported
with Ramp Application Mode.
0
8
16
24
31
Reserved
Enable Texture
Application Mode
Texture Type
KdDDA
KsDDA
Figure 5.44
TextureColorMode Register
The Texel0 register holds the texture value. This may be loaded
automatically by the Texture Read unit, or supplied from the host for a
procedural texture. Fig 5.44 and 5.45 show texture values in RGB and
YUV formats respectively. This register is also used to hold the
background color for the bitmask and stipple tests. If the tests fail then
this color can be used in place of that from the Color DDA unit.
0
8
16
24
31
Alpha
Red
Green
Blue
Figure 5.45
Texel0 Register - RGB and YUV formats
The six registers: KsStart, dKsdx, dKsdyDom, KdStart, dKddx and
dKddyDom hold the start, dx and dyDom parameters for Ks and Kd.
The format is 2's complement 2.16 fixed point format (1 bit sign, 1 bit
integer, 16 bits fraction) with an effective range of ±1.999. The values of
Ks and Kd at each vertex are used to calculate the gradient values in
much the same way as the Z gradients, when interpolating depth see
Appendix D.
The FogMode register is used to enable and disable fogging (qualified
by the fog application bit in the Render command register). Setting Fog
Test causes fragments with negative fog values to be rejected see
section §5.12.2.
Содержание TVP4020 PERMEDIA 2
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