TVP4020
Programmers Reference Manual
Graphics Programming
99
Bottom left origin
Destination address = FBWindowBase - Y * W + X + FBPixelOffset
Source address = FBWindowBase - Y * W + X + FBPixel FBSourceOffset
Top left origin
Destination address = FBWind Y * W + X + FBPixelOffset
Source address = FBWind Y * W + X + FBPixel FBSourceOffset
where:
Destination
Address
is the address in the framebuffer which is written
to if writes are enabled, and is also the address
read when ReadDestination is enabled.
Source Address
is the address in the framebuffer which is read
from when ReadSource is enabled.
X
is the pixel's X coordinate,
Y
is the pixel's Y coordinate,
FBWindowBase
holds the base address in the framebuffer of the
current window.
FBPixelOffset
is normally zero except when multi-buffer writes
are needed when it gives a way to access pixels
in alternative buffers without changing the
FBWindowBase register. This is useful as the
window system may be asynchronously
changing the window's position on the screen. It
is held in the FBPixelOffset register.
FBSourceOffset
is normally zero except during a copy operation
where data is read from one address and
written to another address. The FBSourceOffset
is held in the FBSourceOffset register and is the
offset from destination to source.
W
is the screen width. Only a subset of widths are
supported and these are encoded into the PP0,
PP1 and PP2 fields in the FBReadMode
register. See the table in Appendix C for more
details.
mode it is important to ensure that the buffers which affect the rendering are updated
only once. For example, when rendering with depth buffering enabled, localbuffer writes
should only be enabled for the last buffer updated.
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 ...
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