Section 3     POWERVision(tm) (VGX/VGXT) Graphics Subsystem
The IRIS PowerVision(tm) graphics subsystem is an extremely powerful graphics
subsystem whose performance and features are second only to the IRIS
RealityEngine(tm) in the computer graphics industry. It offers a general purpose
graphics architecture that supports tremendous performance for 3D geometric and 2D
image processing.  This level of graphics processing power is derived from the
incorporation of advanced parallel processing techniques and as many as 85 custom
VLSI ASICs designed by Silicon Graphics.

The basic PowerVision architecture manifests itself in the VGX series of computer
svstems, while the same basic architecture is used for the texture accelerated VGXT
svstems and the Simulation-oriented SkyWriter(tm) Host Integrated Computer Image

PowerVision Graphics includes:

o  24-bit color, double buffered

o  8-bit alpha (transparency), double buffered

o  24-bit Z-buffer

o  8 stencil bitplanes

o  4 Overlay (8 planes, double buffered [optional]) and 8 Window planes

o  1280 x 1024 standard screen resolution

o  Programmable video timing up to HDTV (1920 x 1024 @ 30Hz Interlaced)

o  Support for live video input and output options

o  Optional genlock capability

o  Stereoscopic viewing support/Stereo-ready monitor

Advanced graphics features include hardware support for:

o  Subpixel positioning

o  Advanced lighting models:
    Multiple colored light sources (up to 8)
    Ambient, diffuse, and specular lighting models
    Phong lighting

o  Real-Time Texture Mapping

o  Real-Time Anti-aliasing of all Primitives (polycons, lines, points)

o  Spotlights
    Local and infinite light source positioning
    Two-sided lighting

o  High-speed graphics DMA with pan and zoom capabilities

o  Atmospheric effects

o  Sphere rendering

o  Pixel-blending capabilities for transparency effects