TVP4020
Programmers Reference Manual
Initialization
135
To enable dithering use the following:
ditherMode.XOffset = 0
ditherMode.YOffset = 0
ditherMode.DitherEnable = PERMEDIA_ENABLE
ditherMode.UnitEnable = PERMEDIA_ENABLE
DitherMode(ditherMode)
Note that the Color Format unit is normally always enabled even if
dithering itself is not. This is because the unit handles color formatting as
well as the dithering operation.
6.3.2
Setting the Window Address and Origin.
P
ERMEDIA
supports the concept of a current window origin. The origin of
the window can be specified either as being in the Top Left or Bottom
Left corner. This allows the user to pick the most appropriate
coordinate system to use; for 3D graphics it would typically be bottom
left, whereas for window systems it would be top left. Thus for OpenGL
set:
fbReadMode.WindowOrigin = PERMEDIA_BOTTOM_LEFT_WINDOW_ORIGIN
FBReadMode(fbReadMode)
lbReadMode.WindowOrigin = PERMEDIA_BOTTOM_LEFT_WINDOW_ORIGIN
LBReadMode(lbReadMode)
textureMapFormat.WindowOrigin =
PERMEDIA_BOTTOM_LEFT_WINDOW_ORIGIN
TextureMapFormat(textureMapFormat)
The window origin is set in the Scissor unit. This information usually is
provided by the window system. It will need updating if the window
moves. As an example if the position of the window is (200, 600) (using
a bottom left coordinate system), the origin is specified as follows:
windowOrigin.X = 200
windowOrigin.Y = 600
WindowOrigin(windowOrigin)
The base address of the window must also be established in the
localbuffer read and framebuffer read units. The base address is the
physical address that represents the base address of the window.
Assuming the base address of the framebuffer represents the pixel in
the top left corner of the screen, then for the example above the actual
physical address of the bottom left pixel of the window will be set as
follows:
fbWindowBase = fbBaseA
(fbWidth * (fbHeight-1-600) + 200)
FBWindowBase(fbWindowBase)
Содержание TVP4020 PERMEDIA 2
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