JG82852GMSL7VP Datasheet, PDF (130/176 Pages) Intel Corporation – Intel® 852GM/852GMV Chipset Intel® 852GM/852GMV Chipset Hub (GMCH)

Functional Description
R
Linear MIP Linear (Trilinear MIP Mapping): This is used if many LODs are present. Two
appropriate LODs are selected and a weighted average of a 2x2 area of texels surrounding the
desired pixel in each MIP Map is generated (four texels per MIP Map). The Final texture value is
generated by linear interpolation between the two texels generated for each of the MIP 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 OGL (Rev.1.1) allow support for all these filtering modes.
5.4.2.13.
Multiple 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.
5.4.2.14.
Cubic 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.
5.4.2.15.
Bump Mapping
The GMCH only supports embossed and dot product bump mapping, not environment bump mapping.
5.4.3.
Raster 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 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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Intel^® 852GM/852GMV Chipset GMCH Datasheet