QG82945GSE S LB2R Intel, QG82945GSE S LB2R Datasheet - Page 369

• Manufacturer Part Number: QG82945GSE S LB2R
• Description: GRAPHICS AND MEM CNTRL HUB; No. of Pins: 998; Package / Case: FCBGA; Interface Type: PCI, SATA, USB
• Manufacturer: Intel

Functional Description
10.4.1.6.11 Alpha Blending (Frame Buffer)
10.4.1.6.12 Microsoft DirectX* and SGI OpenGL* Logic Ops
10.4.1.6.13 Color Buffer Formats: 8, 16, or 32 Bits per Pixel (Destination Alpha)
10.4.1.6.14 Depth Buffer
Datasheet
objects). There are two ways to implement the fogging technique: per-vertex (linear)
fogging and per-pixel (non-linear) fogging. The per-vertex method interpolates the fog
value at the vertices of a polygon to determine the fog factor at each pixel within the
polygon. This method provides realistic fogging as long as the polygons are small. With
large polygons (such as a ground plane depicting an airport runway), the per-vertex
technique results in unnatural fogging.
The (G)MCH supports both types of fog operations, vertex and per pixel or table fog. If
fog is disabled, the incoming color intensities are passed unchanged to the destination
blend unit.
Alpha Blending adds the material property of transparency or opacity to an object.
Alpha blending combines a source pixel color (RSGSBS) and alpha (AS) component
with a destination pixel color (RDGDBD) and alpha (AD) component. For example, this
is so that a glass surface on top (source) of a red surface (destination) would allow
much of the red base color to show through.
Blending allows the source and destination color values to be multiplied by
programmable factors and then combined via a programmable blend function. The
combined and independent selection of factors and blend functions for color and alpha
are supported.
Both APIs provide a mode to use bitwise ops in place of alpha blending. This is used for
rubber- banding, i.e., draw a rubber band outline over the scene using an XOR
operation. Drawing it again restores the original image without having to do a
potentially expensive redraw.
The raster engine will support 8-, 16-, and 32-bit color buffer formats. The 8-bit format
is used to support planar YUV420 format, which used only in Motion Compensation and
Arithmetic Stretch format. The bit format of Color and Z will be allowed to mix.
The (G)MCH supports both double and triple buffering, where one buffer is the primary
buffer used for display and one or two are the back buffer(s) used for rendering.
The frame buffer of the (G)MCH contains at least two hardware buffers: the Front
Buffer (display buffer) and the Back Buffer (rendering buffer). While the back buffer
may actually coincide with (or be part of) the visible display surface, a separate (screen
or window-sized) back buffer is used to permit double-buffered drawing. That is, the
image being drawn is not visible until the scene is complete and the back buffer made
visible (via an instruction) or copied to the front buffer (via a 2D BLT operation).
Rendering to one and displaying from the other remove the possibility of image tearing.
This also speeds up the display process over a single buffer. Additionally, triple back
buffering is also supported. The instruction set of the (G)MCH provides a variety of
controls for the buffers (e.g., initializing, flip, clear, etc.).
The raster engine will be able to read and write from this buffer and use the data in per
fragment operations that determine whether resultant color and depth value of the
pixel for the fragment are to be updated or not.
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