Intel D15343-003 manual Raster Engine, Multiple Texture Composition, Cubic Environment Mapping

Intel® 82854 Graphics Memory Controller Hub (GMCH)

Maps. Trilinear MIP Mapping is used minimize the visibility of LOD transitions across the polygon.

•Anisotropic MIP Nearest (Anisotropic filtering): This filter can be used when textured object pixels map back to significantly non-square regions of the texture (e.g., when the texture is scaled in one screen direction than the other screen direction).

Both DirectX and OpenGL (Rev.1.1) allow support for all these filtering modes.

6.4.2.13Multiple Texture Composition

The GMCH also performs multiple texture composition. This allows the combination of two or greater MIP maps to produce a new one with new LODs and texture attributes in a single or iterated pass. The setup engine supports up to four texture map coordinates in as single pass. The GMCH allows up to two Bilinear MIP Maps or a single Trilinear MIP Map to be composited in a single pass. Greater than two Bilinear MIP Maps or more than one Trilinear MIP Map would require multiple passes. The actual blending or composition of the MIP Maps is done in the raster engine. The texture engine provides the required texels including blending information.

Flexible vertex format support allows multi-texturing because it makes it possible to pass more than one texture in the vertex structure.

6.4.2.14Cubic Environment Mapping

Environment maps allow applications to render scenes with complex lighting and reflections while significantly decreasing CPU load. There are several methods to generate environment maps such as spherical, circular and cubic. The GMCH supports cubic reflection mapping over spherical and circular since it is the best choice to provide real-time environment mapping for complex lighting and reflections.

Cubic Mapping supports a texture map for each of the 6 cube faces. These can be generated by pointing a camera with a 90-degree field-of-view in the appropriate direction. Per-vertex vectors (normal, reflection or refraction) are interpolated across the polygon and the intersection of these vectors with the cube texture faces are calculated. Texel values are then read from the intersection point on the appropriate face and filtered accordingly.

6.4.2.15Bump Mapping

The GMCH only supports embossed and dot product bump mapping, not environment bump mapping.

6.4.3Raster Engine

The Raster engine is where the color data such as fogging, specular RGB, texture map blending, etc. is processed. The final color of the pixel is calculated and the RGB value is combined with the corresponding components resulting from the Texture engine. These textured pixels are modified by the specular and fog parameters. These specular highlighted, fogged, textured pixels are color blended with the existing values in the frame buffer. In parallel, stencil, alpha, and depth buffer tests are conducted which will determine whether the Frame and Depth buffers will be updated with the new pixel values.

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