Intel® 945G/945GZ/945GC/ 945P/945PL Express Chipset Family ...

10.5.4 Texture Engine
Functional Description
The GMCH allows an image, pattern, or video to be placed on the surface of a 3D polygon. The
texture processor receives the texture coordinate information from the setup engine and the
texture blend information from the scan converter. The texture processor performs texture color
or ChromaKey matching, texture filtering (anisotropic, trilinear, and bilinear interpolation), and
YUV-to-RGB conversions.
10.5.4.1 Perspective Correct Texture Support
A textured polygon is generated by mapping a 2D texture pattern onto each pixel of the polygon.
A texture map is like wallpaper pasted onto the polygon. Since polygons are rendered in
perspective, it is important that texture be mapped in perspective as well. Without perspective
correction, texture is distorted when an object recedes into the distance.
10.5.4.2 Texture Formats and Storage
The GMCH supports up to 32 bits of color for textures.
10.5.4.3 Texture Decompression
DirectX supports texture compression to reduce the bandwidth required to deliver textures. As the
textures’ average size gets larger with higher color depth and multiple textures become the norm,
it becomes increasingly important to provide a mechanism for compressing textures. Texture
decompression formats supported include DXT1, DXT2, DXT3, DXT4, DXT5, and FXT1.
10.5.4.4 Texture ChromaKey
ChromaKey describes a method of removing a specific color or range of colors from a texture
map before it is applied to an object. For “nearest” texture filter modes, removing a color simply
makes those portions of the object transparent (the previous contents of the back buffer show
through). For “ linear “ texture filtering modes, the texture filter is modified if only the nonnearest
neighbor texels match the key (range).
10.5.4.5 Anti-Aliasing
Aliasing is one of the artifacts that degrade image quality. In its simplest manifestation, aliasing
causes the jagged staircase effects on sloped lines and polygon edges. Another artifact is the
moiré patterns that occur as a result of a very small number of pixels available on screen to
contain the data of a high-resolution texture map. More subtle effects are observed in animation,
where very small primitives blink in and out of view.
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