Elan Graphics
| Company type | Computer graphics architecture |
|---|---|
| Industry | Computer graphics |
| Founded | 1991 |
| Founder | Silicon Graphics |
| Products | Graphics architecture for workstations |
Elan Graphics represents a computer graphics architecture introduced by Silicon Graphics in 1991, positioned as a premium graphics solution for mid-1990s workstations within the Express Graphics series. It delivered real-time 2D and 3D rendering performance comparable to that of high-end personal computers a decade later, with the exception that texture mapping was handled via software rather than hardware.
The Silicon Graphics Indigo Elan platform incorporates four GE7 Geometry Engine processors, collectively providing 128 MFLOPS, alongside a single RE3 Raster Engine capable of rendering 180,000 Z-buffered, lit, and Gouraud-shaded triangles each second. Its framebuffer supports a 56-bit pixel depth, allocating 12 bits per pixel (dithered RGB 4/4/4) for double-buffered, depth-buffered RGB configurations. Additionally, it can function in true 24-bit color mode without employing double-buffering or Z-buffering. Hardware stencil buffering is achieved by reserving 4 bits from the Z-buffer, forming a combined buffer with 20-bit Z and 4-bit stencil capabilities.
Elan Graphics consists of five main components: the HQ2 Command Engine, GE7 Geometry Subsystem, RE3 Raster Engine, VM2 framebuffer, and VC1 Display Subsystem. It supports display resolutions up to 1280 x 1024 pixels with 24-bit color depth and is compatible with unencoded NTSC and PAL analog TV signals. The architecture is implemented across five daughterboards that interface with the primary workstation motherboard.
This design was eventually replaced by SGI's Extreme Graphics on Indigo2 workstations and subsequently succeeded by the IMPACT architecture introduced in 1995.
Features
- Subpixel accuracy in positioning
- Sophisticated lighting techniques including:
- Up to eight distinct colored light sources
- Ambient, diffuse, and specular illumination
- Phong shading model
- Spotlight effects
- Both local and infinite light source placements
- Two-sided lighting support
- Anti-aliased rendering of lines and points
- Comprehensive scene-wide anti-aliasing
- Atmospheric visual effects
- Rendering of spheres
- Pixel blending for transparency simulation
- Soft shadow generation and depth-of-field effects
- Texture mapping
- Support for multimode window environments
- X11 graphics primitives and pixel transfer operations
- Handling of Non-Uniform Rational B-Spline (NURBS) surfaces