Intergraph RealiZm Graphics V25, Hardware User'S Manual

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The following table summarizes the video plane sets for the Z13, Z25, and V25 accelerators.
Video Plane Sets 100 Bits/Pixel 128 Bits/Pixel
Image (red, green, blue), front buffer 24 24
Image (red, green, blue), back buffer 24 24
Overlay, front buffer 4 8
Overlay, back buffer 4 8
Image, VLT selection, front buffer 4 4
Image, VLT selection, back buffer 4 4
Z buffer 24 32
Mask (pixel access control) 2 4
Image, buffer selection control 1 1
Overlay, buffer selection control 1 1
Alpha 0 8
Stencil 6 8
Fast Clear Front Buffer 1 1
Fast Clear Back Buffer 1 1
True-Color Image Buffer
The true-color image buffer is 24 bits and double-buffered. It contains the red, green, and
blue components of the image with 8 bits per component to provide 16.7 million colors.
There are two copies, or buffers, of image data: a front buffer and a back buffer. Two buffers
enhance smooth animation, since applications may update the back buffer while displaying the
front buffer.
High-Resolution Z Buffer
The Z buffer holds 24 bits of depth information (Z10) or up to 32 bits of depth information
(Z13, Z25, and V25). Depth represents a distance from the observer’s eye to an object in a
scene. A large Z buffer enables representation of a large number of unique depth values,
which provides a more accurate rendering of scenes with large depth separation between
objects.
Stencil Buffer (Z13, Z25, and V25)
The stencil buffer holds up to 8-bits of stencil information. This buffer is a general-purpose
resource for OpenGL applications. In a typical case, stenciling inhibits writes to portions of
an application’s window, but allows writes to other portions. The Frame Buffer accelerates
building the values in the stencil buffer, and also accelerates the action of inhibiting or
allowing writes on a per-pixel basis.