Graphics Programming
TVP4020
Programmers Reference Manual
92
PixelsPerEntry
0 = 1 pixel
1 = 2 pixels
2 = 4 pixels
3 = reserved
LUTOffset
DirectIndex
Enable
Reserved
Figure 5.28
TexelLUTMode Register
The LUT must be enabled before a look-up will be done. The other fields
of this register are used to control use of the LUT for 2D operations.
Enabling DirectIndex causes the LUT to be indexed by the address of
the fragment, not by data read from memory. If block fills are used the
LUT is indexed at the start of every scanline based on the lower 3 bits of
the Y value (X is ignored), the LUTOffset which is added to the index,
and the PixelsPerEntry field; two consecutive entries in the LUT are
used to fill the upper and lower halves of the 64 bit block color register.
If block fills are not used the lower 3 bits of the X and Y values of each
fragment are used to index the LUT; the PixelsPerEntry field scales the
X and Y values so that an 8 pixel by 8 pixel pattern is supported, and the
LUTOffset field is added to the index before it is used.
If the LUT is used for 2D operations, the texture application unit should
be enabled and set to copy mode so that the texture color generated by
the look-up table is converted to a color that can be plotted on the
screen.
0
8
16
24
31
24 bit unsigned integer
Reserved
System Memory
Reserved
Figure 5.29
TexelLUTAddress register
If all 256 entries in the LUT need to be filled, the TexelLUTData and
TexelLUTOffset registers should be used. The offset into the LUT for the
first entry to be loaded should be written to the TexelLUTOffset register,
then a succession of LUT entries written to the TexelLUTData register.
The offset into the LUT will be automatically incremented after each
entry is written.
Содержание TVP4020 PERMEDIA 2
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