![background image](http://html.mh-extra.com/html/texas-instruments/tvp4020-permedia-2/tvp4020-permedia-2_reference-manual_1097169095.webp)
Graphics Programming
TVP4020
Programmers Reference Manual
86
the dynamic range of Q is such that it cannot be normalized to the
supported range, the software should either tessellate the triangle into
smaller regions to reduce the range or accept a reduction in accuracy; a
Q value of zero will be handled in a reasonable manner.
If perspective correction is enabled each interpolated S and T value is
divided by the interpolated Q value. The result is passed to the Texture
Read unit which reads the texel from memory.
If subpixel correction has been enabled for a primitive, then any
correction required will be applied to the texture coordinates.
5.7.2
Registers
The S and T values are in 30 bit 2's complement format:
0
8
16
24
31
Integer
Fraction
Reserved
Figure 5.22
Fixed Point S and T Format
The Q values are in 29 bit 2's complement format:
0
8
16
24
31
Reserved
Fraction
Integer
Figure 5.23
Fixed Point Q Format
The registers to set-up Texture interpolation are:
Register
Data Field
Description
Sstart
30 bit 2's comp fix pt
S start value
dSdx
30 bit 2's comp fix pt
S derivative per unit X
dSdyDom
30 bit 2's comp fix pt
S derivative per unit Y, dominant edge
Tstart
30 bit 2's comp fix pt
T start value
dTdx
30 bit 2's comp fix pt
T derivative per unit X
dTdyDom
30 bit 2's comp fix pt
T derivative per unit Y, dominant edge
Qstart
29 bit 2's comp fix pt
Q start value
dQdx
29 bit 2's comp fix pt
Q derivative per unit X
dQdyDom
29 bit 2's comp fix pt
Q derivative per unit Y, dominant edge
Table 5.16
Texture Interpolation Registers
Summary of Contents for TVP4020 PERMEDIA 2
Page 1: ...Texas Instruments TVP4020 PERMEDIA 2 Programmer s Reference Manual Issue 4 ...
Page 284: ...TVP4020 Programmers Reference Manual A Gouraud Shaded Triangle 275 ...
Page 292: ...TVP4020 Programmers Reference Manual Register Tables 283 ...
Page 314: ...TVP4020 Programmers Reference Manual Index 305 ...
Page 315: ...Index TVP4020 Programmers Reference Manual 306 Index ...
Page 323: ...Index TVP4020 Programmers Reference Manual 314 ...