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TVP4020
Programmers Reference Manual
Graphics Programming
89
The width used to repeat or clamp can be different to the width used to
set the stride of the texture in memory. This allows a texture to be
selected from part of a larger image.
5.8.2
Texture Base Address
The base address of the texture map is set in the TextureBaseAddress
register. The lower 24 bits of this field specify the address of the map in
texels. Bit 30 is used to specify that the texture is held in system memory
instead of local memory and the texture should be ‘executed’ directly
across the PCI bus without first copying the texture to local memory.
Refer to the
TVP4020 Hardware Reference Manual for more details.
The base address of the texture may be loaded indirectly from memory
using the TextureID register. The value loaded into this register should
be the address in memory of the base address of the texture (specified
in 32 bit units). Loading the TextureID register causes the real base
address to be loaded from memory. If bit 31 of the value loaded is set,
the value is interpreted as invalid, the graphics processor halted, and an
interrupt issued to the CPU. This mechanism is normally used to indicate
that the required texture is not resident in local memory and should be
copied in. Once the copy has been completed and the texture base
address in memory is updated with its invalid bit clear, the graphics
processor re-reads this value and restarts. Refer to the
TVP4020
Hardware Reference Manual for details on loading textures while the
Graphics Processor has stalled.
5.8.3
Texture Filtering
A bilinear filter is available which combines the values of the 4 texels
surrounding the index into the texture map to produce a single value.
This filter will reduce pixelation effects when textures are enlarged, and
reduce aliasing effects when textures are shrunk.
5.8.4
Texture Formatting
The texture map can be held in memory in a variety of formats that
correspond to the formats supported by the framebuffer. Two additional
formats are provided to allow texture maps to be stored in YUV color
format. When a texel is read into P
ERMEDIA
it is converted to the internal
color format. External color formats are shown in table 4.1. Note: the
color format value is made up of the 4 bits of the TextureFormat field
and the 1 bit TextureFormatExtension field in the TextureDataFormat
register.
If the selected format has no alpha buffer, a default value of 0xFF, which
is the maximum is used. If the NoAlphaBuffer bit is set in the
TextureDataFormat register then 0xFF is used even if the format has an
alpha buffer.
Содержание TVP4020 PERMEDIA 2
Страница 1: ...Texas Instruments TVP4020 PERMEDIA 2 Programmer s Reference Manual Issue 4 ...
Страница 47: ...Memory I O and Organization TVP4020 Programmers Reference Manual 38 Texture address TextureBaseAddress T W S ...
Страница 284: ...TVP4020 Programmers Reference Manual A Gouraud Shaded Triangle 275 ...
Страница 292: ...TVP4020 Programmers Reference Manual Register Tables 283 ...
Страница 314: ...TVP4020 Programmers Reference Manual Index 305 ...
Страница 315: ...Index TVP4020 Programmers Reference Manual 306 Index ...
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