JG82855GMESL7VN Datasheet, PDF (142/213 Pages) Intel Corporation – Intel® 855GM/855GME Chipset Graphics and Memory Controller Hub (GMCH)

Functional Description
R
6.4.2.1
6.4.2.2
6.4.2.3
6.4.2.4
• Bilinear, Trilinear, and Anisotropic MIP map filtering
• Gouraud shading and Flat shading
• Alpha-blending
• Per-Vertex and per- pixel fog
• Z/W buffering
These features are independently controlled via a set of 3D instructions. The 3D pipeline
subsystem performs the 3D rendering acceleration. The main blocks of the pipeline are the Setup
Engine, Scan Converter, Texture Pipeline, and Raster Pipeline. A typical programming sequence
would be to send instructions to set the state of the pipeline followed by rendering instructions
containing 3D primitive vertex data.
Bi-Cubic Filtering (Intel^® 855GME GMCH)
Bi-Cubic filtering is an alternate method to Bi-Linear filtering. The filter (blend factor) is
determined by the relative distance between the pixel center and the nearest 4 texel (2X2). This
method provides a significant level of filtering and looks very crisp on a display. This method
also creates a smooth motion of texture as it traverses across the display.
Video Mixer Rendering (Intel^® 855GME GMCH)
VMR refers to the ability to blend any data format/source with other displayable content. It allows
3D, video/DVD, 2D bitmap and closed caption to be mixed together. VMR works mainly as a
front-end processor, thereby reducing dependence on video ports and overlays
Setup Engine
The GMCH 3D setup engine takes the input data associated with each vertex of a 3D primitive
and computes the various parameters required for scan conversion. In formatting this data, the
GMCH maintains sub-pixel accuracy. The per-vertex data is converted into gradients that can be
used to interpolate the data at any pixel within a polygon (colors, alpha, Z or W depth, fog, and
texture coordinates). The pixels covered by a polygon are identified and per-pixel texture
addresses are calculated.
Viewport Transform and Perspective Divide
A 3D-geometry pipeline typically involves transformation of vertices from model space to
clipping space followed by clip test and clipping. Lighting can be performed during the
transformation or at any other point in the pipeline. After clipping, the next stage involves
perspective divide followed by transformation to the viewport or screen space. The GMCH can
support viewport transform and perspective divide portion of the 3D geometry pipeline in
hardware.
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Datasheet