Elan Graphics is a
computer graphics architecture for
Silicon Graphics computer workstations. Elan Graphics was developed in 1991 and was available as a high-end graphics option on workstations released during the mid-1990s as part of the
Express Graphics
Express or EXPRESS may refer to:
Arts, entertainment, and media Films
* '' Express: Aisle to Glory'', a 1998 comedy short film featuring Kal Penn
* '' The Express: The Ernie Davis Story'', a 2008 film starring Dennis Quaid
Music
* ''Express'' ...
architectures family. Elan Graphics gives the workstation real-time 2D and
3D graphics
3D computer graphics, or “3D graphics,” sometimes called CGI, 3D-CGI or three-dimensional computer graphics are graphics that use a three-dimensional representation of geometric data (often Cartesian) that is stored in the computer for the ...
rendering capability similar to that of even high-end
PCs made over ten years after Elan's introduction, with the exception of
texture mapping, which had to be performed in software.
The Silicon Graphics Indigo Elan option Graphics systems consist of four GE7
Geometry Engine
Geometric manipulation of modelling primitives, such as that performed by a geometry pipeline, is the first stage in computer graphics systems which perform image generation based on geometric models. While geometry pipelines were originally implem ...
s capable of a combined 128
MFLOPS
In computing, floating point operations per second (FLOPS, flops or flop/s) is a measure of computer performance, useful in fields of scientific computations that require floating-point calculations. For such cases, it is a more accurate meas ...
and one RE3
Raster Engine
Raster may refer to:
* Raster graphics, graphical techniques using arrays of pixel values
* Raster graphics editor, a computer program
* Raster scan, the pattern of image readout, transmission, storage, and reconstruction in television and comput ...
. Together, they are capable of rendering 180K Z-buffered, lit,
Gouraud-shaded
Gouraud shading, named after Henri Gouraud, is an interpolation method used in computer graphics to produce continuous shading of surfaces represented by polygon meshes. In practice, Gouraud shading is most often used to achieve continuous li ...
triangles per second. The framebuffer has 56 bits per pixel, causing 12-bits per pixel (dithered RGB 4/4/4) to be used for a double-buffered, depth buffered, RGB layout. When double-buffering isn't required, it is possible to run in full 24-bit color. Similarly, when Z-buffering is not required, a double-buffered 24-bit RGB framebuffer configuration is possible. The Elan Graphics system also implemented hardware
stencil buffering by allocating 4 bits from the Z-buffer to produce a combined 20-bit Z, 4-bit stencil buffer.
Elan Graphics consists of five graphics subsystems: the HQ2 Command Engine, GE7 Geometry Subsystem, RE3 Raster Engine, VM2
framebuffer and VC1 Display Subsystem. Elan Graphics can produce resolutions up to 1280 x 1024 pixels with 24-bit color and can also process unencoded
NTSC and
PAL analog
television signals. The Elan Graphics system is made up of five
daughterboards that plug into the main workstation
motherboard
A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expand ...
.
The Elan Graphics architecture was superseded by SGI's
Extreme Graphics architecture on
Indigo2
The O2 is a large entertainment district on the Greenwich peninsula in South East London, England, including an indoor arena, a music club, a Cineworld cinema, an exhibition space, piazzas, bars, and restaurants. It was built largely within ...
models and eventually by the
IMPACT graphics architecture in 1995.
Features
* Subpixel positioning
* Advanced lighting models:
* Multiple colored light sources (up to 8)
* Ambient, diffuse, and specular lighting models
*
Phong lighting
* Spotlights
* Local and infinite light source positioning
* Two-sided lighting
* Anti-aliased lines and points
* Full scene anti-aliasing
* Atmospheric effects
* Sphere rendering
* Pixel-blending capabilities for transparency effects
* Soft shadows and depth-of-field
*
Texture-mapping
* Multimode windowing environment
* X11 drawing primitives and pixel move operations
* Non-Uniform Rational B-Spline (
NURBS) surfaces
References
External links
ElanTR - Elan Graphics Technical Report
{{Silicon Graphics
Graphics chips
SGI graphics