301467-005 Datasheet, PDF (240/426 Pages) Intel Corporation – Express Chipset

Functional Description
R
12.6.3.9
Cubic Environment Mapping
Environment maps allow applications to render scenes with complex lighting and reflections
while significantly decreasing processor 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 requires 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 is calculated. Texel values are then read from the intersection
point on the appropriate face and filtered accordingly.
12.6.4
12.6.4.1
12.6.4.2
12.6.4.3
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 RGBA 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.
Texture Map Blending
Multiple Textures can be blended together in an iterative process and applied to a primitive. The
GMCH allows up to four texture coordinates and texture maps to be specified onto the same
polygon. Also, the GMCH supports using a texture coordinate set to access multiple texture maps.
State variables in multiple texture are bound to texture coordinates, texture map or texture
blending.
Combining Intrinsic and Specular Color Components
The GMCH allows an independently specified and interpolated “specular RGB” attribute to be
added to the post-texture blended pixel color. This feature provides a full RGB specular highlight
to be applied to a textured surface, permitting a high-quality reflective colored lighting effect not
available in devices which apply texture after the lighting components have been combined. If
specular-add state variable is disabled, only the resultant colors from the map blending are used.
If this state variable is enabled, RGB values from the output of the map blending are added to
values for RS, GS, BS on a component by component basis.
Color Shading Modes
The Raster Engine supports the flat and Gouraud shading modes. These shading modes are
programmed by the appropriate state variables issued through the command stream.
Flat shading is performed by smoothly interpolating the vertex intrinsic color components (Red,
Green, Blue), Specular Highlights(R,G,B), Fog, and Alpha to the pixel, where each vertex color
has the same value. The setup engine substitutes one of the vertex’s attribute values for the other
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Datasheet