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Graphics Programming
TVP4020
Programmers Reference Manual
44
The texture parameters (S, T and Q) are handled differently to the other
parameters as their range must be constrained to get the best results
from the finite precision DDA and perspective division hardware
available in the Graphics Processor. Any operation on the texture
parameters before they are used is controlled by the
TextureParameterMode in the DeltaMode register. The options are
NoClamp, Clamp or Normalize. The NoClamp and Clamp options work
the same as for the other parameters. The Normalize option finds the
maximum absolute value of the texture S, T and Q values for the
primitive and normalizes all the value to lie in the range -1.0 … 1.0
inclusive prior to being used in the set-up calculations. Note that the
texture values in the vertex store are
not changed by the Normalize
option to allow normalization to work on a triangle by triangle basis
across a triangle mesh.
5.2.1
Drawing Commands
The Delta Unit responds to five drawing commands: DrawTriangle,
RepeatTriangle, DrawLine01, DrawLine10 and RepeatLine. When using
Delta, these drawing commands replace the Render command, and
have the same data field.
The Draw and Repeat commands cause Delta to calculate the required
data for the rendering devices and update the Start, dX and dyDom
registers in the Rasterizer, Color, Depth, Texture and Fog Units of the
Graphics Processor. Any additional registers in the Rasterizer Unit are
also loaded (N.B. the RasterizerMode register is not updated). Finally
the Render and ContinueNewSub commands are sent to the rendering
devices.
The data field accompany the DrawTriangle or DrawLine command is
used to control some aspects of the Delta's operation in conjunction with
the DeltaMode register. The relevant bits in the Draw command, and
their effect in the Delta Unit are described in Table 5.2. Note that the
values in the remaining bits must be compatible with the desired
operation.
Bit
No.
Name
Description
13
TextureEnable
When set (and qualified by the TextureEnable bit in the
DeltaMode register) causes the texture values (S, T and
Q) to be calculated.
14
FogEnable
When set (and qualified by the FogEnable bit in the
DeltaMode register) causes the fog values to be
calculated.
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 ...