Datasheet

Functional Description
R
186 Datasheet
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.
5.4.3.1 Texture Map Blending
Multiple Textures can be blended together in an iterative process and applied to a primitive. The
GMCH allows up to four distinct or shared texture coordinates and texture maps to be specified
onto the same polygon. Also, the GMCH supports a texture coordinate set to access multiple
texture maps. State variables in multiple textures are bound to texture coordinates, texture map or
texture blending.
5.4.3.2 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, the specular RGB color is added to the RGB values from the
output of the map blending.
5.4.3.3 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 (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 two vertices attribute values thereby creating the correct flat shading terms. This
condition is set up by the appropriate state variables issued prior to rendering the primitive.
• Gouraud shading is performed by smoothly interpolating the vertex intrinsic color
components (Red, Green, Blue). Specular (RGB), Fog, and Alpha to the pixel, where each
vertex color has a different value. All the attributes can be selected independently to one of
the shading modes by setting the appropriate value state variables.