TVP4020
Programmers Reference Manual
A Gouraud Shaded Triangle
281
D9
Rasterizer Mode
The P
ERMEDIA
Rasterizer has a number of modes which remain effective
from the time they are set until they are modified and can thus affect
many primitives. In the case of the Gouraud shaded triangle, the default
values for these modes are suitable.
RasterizerMode (0)
// Default Rasterizer mode
D10
Subpixel Correction
P
ERMEDIA
can perform subpixel correction of all interpolated values when
rendering aliased trapezoids. This correction ensures that any
parameter (color/depth/texture/fog) is correctly sampled at the center of
a fragment. In general, subpixel correction will always be enabled when
rendering any trapezoid which has interpolated parameters. Control of
subpixel correction is in the Render command register described in the
next section, and is selectable on a per primitive basis. It does not need
to be enabled for any primitive that does not use interpolation, including
copy operations. If it is disabled and interpolators are used, the values
calculated for the primitive may not be exactly correct; enabling sub-pixel
correction may reduce the performance of the chip, particularly for small
primitives.
D11
Rasterization
P
ERMEDIA
is almost ready to draw the triangle. Setting up the registers as
described here and sending the Render command will cause the top half
of the example triangle to be drawn.
For drawing the example triangle, all the bit fields within the Render
command should be set to 0 except the PrimitiveType which should be
set to trapezoid and the SubPixelCorrectionEnable bit which should be
set to TRUE.
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 ...