RealityEngine in Visual Simulation

Technical Overview

Table of Contents

Section 2: Introduction

2.1 Product Overview

2.2 A New Image Generator Approach

2.2.1 The Next Generation of Image Generators
2.2.2 IRIS Performer and Reality Engine

2.3 Applications

3.1 Architectural Overview

3.1.1 The Geometry Engine
3.1.2 The Raster Manager
3.1.3 Display Subsystem
3.1.4 VideoSplitter/2

3.2 Chassis Configuration

3.2.1 Deskside Chassis
3.2.2 SkyWriter Rack Chassis
3.2.3 POWER Series Rack Rack Chassis

4.1 System Configuration

4.2 Graphics Board Level Options

5.1 Overall System Performance

5.2 Texture

5.2.1 Components
5.2.2 Texture Memory Configuration

5.3 Types and Methods

5.3.1 Non MIPmapped Texture Functions
5.3.2 MIPmapped Texture Functions
5.3.3 Texture Performance

5.4 Anti-aliasing

5.5 Hidden Surface Removal

5.6 Polygon Capabilities

5.6.1 Color
5.6.2 Smooth Shading
5.6.3 Color Blending
5.6.4 Lighting
5.6.5 Atmospheric Effects
5.6.6 Polygon Performance

5.7 Video and Display Output

5.7.1 Programmable Video Timing
5.7.2 Standard Formats
5.7.3 Composite Output
5.7.4 Genlock
5.7.5 Multichannel Video Output

6.1 The HI-CIG Concept

6.2 Computational Capabilities

6.3 Real-time Operating System

6.3.1 REACT
6.3.2 Deterministic Response

6.4 Development Environment

7.1 Advantages

7.2 The Main Elements

7.2.1 The Rapid Rendering Library
7.2.2 The Image Generation Library

7.3 Key Functions

7.3.1 Database Structure and Traversal
7.3.2 Scene Culling
7.3.3 Level-of-Detail Management
7.3.4 System Load Management
7.3.5 Database Query
7.3.6 Environmental Control
7.3.7 Visual Effects

7.4 The Sample Application

8.1 The Silicon Graphics Product Range

8.2 Database Modeling

8.3 Other Application Areas

Credits

The traditional approach to image generation requirements is to deisgn a system that conforms to set specification and performance criteria, with little or no deviation from this original design. Such an approach has the advantage that the system is a known quantity and typically performs in a very predictable manner. The disadvantage is that the system is not open in its approach, providing limited scope for evolution or modification and little opportunity for the application developer to provide added value.

The ideal solution would be a system that provides the basic functions, features, and guaranteed deterministic performance that is a baseline requirement of image generators, as well as providing the flexibility to add to and enhance the system in a way that provides up-to-date capabilities long after purchase.

RealityEngine meets these criteria in a system that is designed from the outset to meet the performance and functional needs of the low-cost image generator. Subsampled anti-aliasing, extensive real-time texture mapping, a highly configurable multi-channel environment, steady frame rates, and performance criteria tuned for complex scene generation are just some of these. In addition, a new simulation software environment, IRIS Performer, is now an integral part of the RealityEngine total solution. IRIS Performer provides the application developer with a suite of highly tailored tools to assemble a visual simulation application rapidly. Using standard multiprocessor RISC processors and a real-time executive, it provides a highly deterministic and predictable environment for the simulation. It is, however, open in nature and can be customized and extended.

2.1 Product Overview

RealityEngine follows the tradition of a long line of Silicon Graphics products; it is binary compatible and upgradeable from previous systems. Designed to address the low-cost image generation market, it offers the following key features:

• High-performance, quality anti-aliasing, up to 16 subsamples per pixel

• Extensive texture capability

  4MB of on-line texture memory standard

  virtual texture page access provided with 50M texel per second download rate and system software control

• Unique, texture image quality and features:

  Trilinear MIPmapping

  Detail Texture

  Sharp Texture

  Projected Texture

  3D Texture

  Multiple channels - up to four high-resolution (1280x1024) outputs per system

  Z-buffer (up to 32-bit) used for all hidden surface removal. Z depth calculations performed with anti-aliasing and transparency

  Up to 12 bits per component RGBA color capability

  1, 2, 3 and 4 component textures - 4, 8 and 12 bits per texture component

  Photomap texture capability with maximum size of 1024x1024 texels

  Fade level of detail

  Steerable, independent spotlights with user-definable lobe shape

  Projected shadows onto 3D terrain

  Lightpoint support

  Animation sequences using texture and geometry

  Atmospheric effects

  Built-in host capability

  Mission functions (height above terrain, collision detection, laser ranging, etc.)

  User-definable video formats

  Load management functions

  64 subpixel (on an 8x8 grid) resolution used throughout

  Simulation specific development environment

  
  

  Key performance and capacity attributes:

  7000 anti-aliased textured polygons per pipeline at 30Hz, 1280x1024 pixel resolution (average depth complexity of 4)

  Up to 320 Million anti-aliased, trilinear MIPmap textured, Z-buffered pixels per second fill rate per graphics pipeline

  Up to 5.2 million displayable pixels per system (2.6 million pixels anti-aliased plus 2.6 million non anti-aliased, or 3.9 million subsample anti-aliased pixels total)

  83 millisecond transport delay at 30Hz update with 60Hz refresh rate

  Up to six output channels per pipeline

  
  

2.2.1 The Next Generation of Image Generators

Market requirements are changing rapidly. While low-cost, high-performance image generators are required for new, emerging simulation applications, new systems must also evolve with the times. It is becoming increasingly important that image generators be able to be tuned to meet unique and unforeseen requirements. Upgradeability and handling of key special effects are increasingly important - in addition to the traditional criteria of image quality, performance, and determinism.

RealityEngine meets the new requirements with hardware-tuned performance and image quality and a software development environment designed to provide the deterministic response and feature capabilities of the image generation market of today and the future.

2.2.2 IRIS Performer and Reality Engine

IRIS Performer is an application development environment, provided as part of RealityEngine, designed to help developers construct real-time visual simulation applications quickly and easily. The advantages of this approach are:

• high performance on an open architecture system

• rapid specific application development

• rich feature functionality with unique and growing capabilities

• enhanced portability to successive hardware enhancements

  
  

RealityEngine is not only designed to address low-end and mid-range visual simulation applications for development and training, but due to the inherently flexible nature of the system, it extends simulation into the realm of visualization, entertainment, and virtual reality applications.

Some examples of applications for which RealityEngine addresses visual system requirements are:

• Flight Simulation.

  Low-cost visuals for part task, procedures, and focused skills training. Visuals for airframe design and development rigs. Fixed and rotary wing mission simulation, low altitude terrain and high-altitude maneuvers training. Visual systems for commercial aircraft training simulators. Among the system features, RealityEngine provides lighting, atmospheric effects, and photomapped texture capabilities.

• Marine Simulation.

  Ship's bridge multichannel visuals for procedures training, maneuverability training, and pilot training. Port evaluation and research, human factors and ship-based design studies. Periscope simulation and remotely piloted undersea vehicle training. Maritime based helicopter training. Harbor management systems simulation. Z-buffer based RealityEngine enables full interaction of ships and other objects with a moving, variable sea state.

• Armored Vehicle training.

  Armored vehicle and gunnery training systems for team combat and individual skills training. RealityEngine provides special effects such as smoke, muzzle flash, and dynamic terrain capabilities.

• Distributed Simulation Environments.

  Simulation environments where a number of simulators operate in a networked environment for team training and scenario evaluation. The multiprocessing computational capabilities of RealityEngine provide the ability to control and simulate the high-performance networking, peripheral and I/O systems required.

• Driving Simulation.

  Simulators for future vehicle research, design, and development of vehicle electronic systems, human factors research, handling, power train, and evaluations. Driver training for a range of ground vehicles, safety training, and accident inquiries. RealityEngine provides extensive photomap texture image capability as well as fast system response. Database feedback functions enable collision detection and feedback of tire-ground contact parameters. Host functions provide vehicle simulation capability.

• Virtual Reality.

  3D visualization of simulated and synthetic scenarios requiring dynamic interaction and rapid response. Immersive simulation environments such as helmet-mounted sensor fusion applications. RealityEngine provides the special effects capabilities and levels of realism required of this type of application. RealityEngine's highly-flexible line rate outputs and I/O capabilities permit connection to a wide variety of peripheral devices.

• Space.

  Procedures training and maneuvers evaluation. Feasibility and human factors studies. Vehicle and system layout, design and testing. Docking and maneuvers training. Lighting and special effects capabilities on the RealityEngine enable critical motion and position cues, such as shadow casting and reflection simulation.

  
  

The architecture of the RealityEngine is designed to provide a flexible and extensible approach to image generation. Data in the graphics pipeline is processed in stages, from the initial IRIS Graphics Library calls in the CPU across the MPLink bus through the pipeline to the final analog or digital video output. The process begins in the CPU, where the application sends data to the graphics subsystem across the bus to the graphics pipeline. This is implemented in an immediate mode fashion and thus there is no necessary correlation between the data sent down in one viewable frame to the next. This has considerable advantages when dealing with rapidly changing data, and displaying changing geometry. One example of this would be dynamic terrain.

Extensive use is made of custom VLSI ASICs for maximum performance and capability within the pipeline. Depending upon the number of Raster Manager (RM) boards, there can be up to 180 custom processors in the pipeline. Most of these processors run in parallel using a Multiple Instruction Multiple Data (MIMD) model. Nine unique ASIC designs are used in the various stages of the pipeline.

FIGURE 1 Reality Engine System Architecture Showing Single and Dual Pipeline Configurations

3.1.1 The Geometry Engine

The first stage of the pipeline is the Geometry Subsystem, which resides on the Geometry Engine (GE) board. The two parts of this stage handle the transfer of data from the bus to the pipeline and the processing of the geometric data as it enters the pipeline. At each stage of the pipeline, optimum performance depends upon maximum utilization of available processing power with as little waiting as possible. Extensive use of FIFOs insures that no stage of the pipeline keeps any other stage waiting.

3.1.2 The Raster Manager

The Raster Subsystem resides on the Raster Manager (RM) board and contains the great bulk of the custom VLSI processors and graphics system memory. The data received by the RM must be scan-converted into pixel data, then processed into the frame buffer before control is handed off to the Display Subsystem. Image memory is interleaved among the parallel processors such that adjacent pixels (or subpixels) are always being processed by different processors.

The Raster Manager contains the frame buffer memory, texture memory and all the processing hardware responsible for color allocation, subpixel anti-aliasing, fogging, lighting, and hidden surface removal.

3.1.3 Display Subsystem

The Display Subsystem takes the digital frame buffer and processes the pixels through digital-to-analog converters (DACs) to generate an analog pixel stream which may then be sent across coaxial cable to display devices as component video. Advanced hardware in the display subsystem supports programmable pixel timings to allow the system to drive displays with resolutions, refresh rates, and interlace/non-interlace characteristics different from those of the standard RealityEngine display monitor. The programmable pixel clock has a table of available video formats (such as 1280x1024@60Hz Non-interlaced or VGA [640x497@60Hz NI], NTSC, PAL, and HDTV). A high-resolution 21" multisync monitor with a display capability up to 1600x1200 @ 60Hz NI is standard.

3.1.4 VideoSplitter/2

Video splitting technology is offered as an option with RealityEngine. This greatly increases the flexibility and output capability of the RealityEngine system. Known as VideoSplitter/2, this next-generation product is a board that resides in the VME chassis and uses one slot. It is capable of driving as many as six outputs, or channels, from a graphics pipeline. These channels can be output at two different line rates: two channels at one rate and four at the other. The VideoSplitter/2 has a bandwidth of 2.6 million pixels, which means that it is capable of driving two high-resolution displays (1280x1024) either from two RM cards, or four RM cards (subsample anti-aliased). Since VideoSplitter/2 is tightly integrated into the display generation system, it does not incur an extra frame transport delay, as was the case with video splitting technology on previous architectures. VideoSplitter/2 is entirely software controlled.

RealityEngine is available in four chassis configurations and a number of board level configurations to address an extensive range of flexible channel options. The three chassis configurations focus on compact size, graphics, and computational requirements respectively.

3.2.1 Deskside Chassis

This unit can either support one MIPS R4000 RISC CPU in the IRIS Crimson chassis or as many as four multiprocessor MIPS R3000 CPUs in the POWER Series chassis. Each type of deskside unit supports one RealityEngine graphics pipeline. The pipeline can be configured with up to two Raster Manager boards [or four for Crimson and 2 CPU POWER Series versions]. It can support one VideoSplitter/2 board, enabling an output range of up to two high-resolution outputs (1280x1024) (one only with subsample anti-aliasing) to six low-resolution outputs (700x600), (four (640x512) with subsample anti-aliasing).

FIGURE 2 Reality Deskside Chassis

Crimson Chassis

Computer Processor
MIPS R4000SC

CPU Performance
85 MIPS
16 MFLOPS
70 SPEC

Memory
16 to 256MB

Max Formatted Disk Capacity
7.2GB internal, 74.4GB external

Max Output Ranges with VideoSplitter/2 and 4 RMs
From 2 high-resolution (1280x1024) displays to 6 low-resolution (700x600) displays

Computer Processors
1 to 4 MIPS R3000

CPU Performance
30 to 143 MIPS
5.1 to 42 MFLOPS
25 to 106 SPEC

Memory
16 to 256MB

Max Formatted Disk Capacity
7.2GB internal, 74.4GB external

Max Output Ranges with VideoSplitter/2 and 4 RMs
From 2 high-resolution (1280x1024) displays to 6 low-resolution (700x600) displays

Note: Four raster Manager configurations only available in two-processor and Crimson versions of deskside chassis.

3.2.2 SkyWriter Chassis

The SkyWriter rack is ideal where large numbers of multiple channels are required. It is capable of driving 5.2 million displayable pixels from a single system (2.6 million pixels with subsample anti-aliasing and 2.6 million pixels without), or a total of up to 3.9 million textured pixels with subsample anti-aliasing. Thus, the SkyWriter chassis can be configured to drive up to three high-resolution (1280x1024) , or up to 10 low-resolution (640x512) subsample anti-aliased outputs. The system can support a maximum of 12 outputs in total. SkyWriter supports two graphics subsystem pipelines.

FIGURE 4 SkyWriter Rack Chassis Configuration

Computer Processors
1 to 4 MIPS R3000

CPU Performance
50 to 143 MIPS
20 to 42 MFLOPS
47 to 106 SPEC

Memory
16 to 256MB

Max Formatted Disk Capacity
31.2GB internal, 81.6GB external

Max Output Ranges with VideoSplitter/2 and 4 RMs
Up to three subsample anti-aliased, high resolution (1280x1024) outputs or 10 low resolution (640x512) anti-aliased displays. Alternatively up to four high resolution displays (2 with anti-aliasing and two without), or up to 12 low resolution displays (6 with anti-aliasing).

Note: The SkyWriter chassis can be extended to have up to 6 RM boards, 4 CPUs and two VideoSplitter/2 boards in total.

3.2.3 POWER Series Rack Chassis

The POWER Series Rack is ideal in applications where there is a heavy computational requirement in the simulation. Supporting up to eight CPUs in parallel, this system can provide extensive host functionality, in conjunction with the image generation. This configuration is capable of driving up to two high-resolution channels (1280x1024), three medium-resolution (1024x768), or six low-resolution channels (700x600), all subsample anti-aliased.

FIGURE 5 POWER Series Rack Chassis Configuration

Computer Processors
1 to 8 MIPS R3000

CPU Performance
30 to 286 MIPS
5.1 to 70 MFLOPS
25 to 166 SPEC

Memory
8 to 256MB

Max Formatted Disk Capacity
31.2GB internal, 115.2GB external

Max Output Ranges with VideoSplitter/2 and 4 RMs
Up to 2 high resolution (1280x1024) subsample anti-aliased display output, 3 medium (1024x768) or up to 6 low resolution (700x600) anti-aliased outputs.

Note: The POWER Series Rack Chassis supports a single RealityEngine subsystem.

When configuring a system, it is important to consider system requirements and capabilities. RealityEngine is configurable at a number of different levels, resulting in economical image generation solutions that are tuned to specific requirements.

• System

  Multiple systems can be simply networked together to provide multiple display capability using Ethernet or shared memory configurations.

• Pipeline

  SkyWriter provides two complete graphics subsystems, or pipelines from a single system.

• Video Channels

  The VideoSplitter/2 provides multiple display outputs, or channels to individual monitors or display devices from a single pipeline graphics subsystem.

• Raster Manager

  These boards provide additional anti-aliased pixel fill rate throughput and frame buffer memory.

• CPU

  The computational subsystem is extensible up to 8 CPUs, allowing extensive scene management and real-time integral host capabilities.

RealityEngine is a highly reconfigurable graphics environment. The base system includes one Raster Manager (RM) board and supports up to 1280x1024 of frame buffer area into which graphics may be rendered. The addition of subsequent RM boards adds capacity (through additional pixel processors) as well as resolution.

TABLE 1 RealityEngine, Permissible Channel, and CPU Configuration

[(*) The original document says 1-2; this is true if more than 2 processors are present, but it is 1-4 if no more than 2 processors are present. The original document also says 1-2 for Crimson, but this is a mistake; it is made clear on pp. 9 that Crimson can have 1-4 RMs]

In conjunction with the VideoSplitter/2, RealityEngine can be configured to support one to twelve output channels from a single system. Each chassis supports one pipeline, except SkyWriter which supports two. Each chassis subsystem can support one video splitter board, except SkyWriter which can be configured with two. Each VideoSplitter/2 board can drive up to six outputs with two different video line rates.

A graphics pipeline can be potentially configured with 3, 4 or 6 graphics boards depending on system configuration constraints. There are three types of board: GE = Geometry Engine, RM = Raster Manager, DG = Display Generator. The optional video splitter (VS) provides up to six channel outputs per pipeline. There are three primary configurations: one, two and four RM. The four RM system has two variants, the first with a single 1280x1024 resolution output and the second being two 1280x1024 resolution outputs. The main difference is that the former supports extremely high pixel quality and throughput.

FIGURE 6 Configurations For a Single Pipeline

The SkyWriter chassis supports the two RM configurations on both pipelines and the four RM configuration on the first pipeline (pipe 0) only. This means that a SkyWriter chassis is capable of generating up to 3 high-resolution outputs with subsample anti-aliasing at 1280x1024 resoltuion.

The number of Raster Manager boards also determines the bit depth of each pixel and thus the quality and performance with which the pixel is drawn. The pixel depth determines the depth of Z-buffer, the number of subsamples available for anti-aliasing and the number of bits per component available for color rendering.

Section 5: Features and Performance

5.1 Overall System Performance

Because RealityEngine has been tuned to address the needs of the visual simulation image generation market, many of the features and capabilities are directly aimed at image generation. The primary areas of focus for performance tuning of the RealityEngine are:

• Textured polygon throughput

  In excess of 210K textured anti-aliased polygons per second throughput capacity through the Geometry Engine section of the pipeline, enabling scenes of extreme complexity at high frame rates.

• Textured fill rates

  Up to 320 million pixels per second for anti-aliased, trilinear, MIPmapped, Z-buffered, lit, smooth, shaded polygons.

• Anti-aliasing performance and capabilities

  Incurring no performance penalty for anti-aliasing, RealityEngine is able to generate high-quality imagery at high-performance.

• Pipeline elasticity

  FIFOs located before and after the Geometry Engine ensure that maximum concurrence is maintained throughout the pipeline. Thus, when the rendering subsystem is busy, the geometry subsystem is still able to operate in parallel. This results in a balanced load on the system and maximum throughput.

• Pixel output capabilities

  A 2.6 Mpixel bandwidth bus at the back end of the display subsystem enables up to two high-resolution (1280x1024) outputs driven from each pipeline. The display subsystem can be configured to generate custom line rate outputs.

• Texture memory access

  50MBytes per second texture download times from host into texture memory enable rapid paging of on-line textures, in turn enabling virtual memory capability for real-time loading of photorealistic texture maps.

  
  

5.2 Texture

RealityEngine has been designed from the start to be able to display complex, texture mapped scenes at high (30-60Hz) frame rates. Maintaining compatibility with the earlier PowerVision and SkyWriter systems was an important design goal; dramatically improved performance and image quality was primary.

Textures may be derived from actual photographs or generated synthetically. They may contain full or partial transparency at any point and support full RGBA true color. The following sections detail the various methodologies utilized to achieve this high-quality, realistic imagery.

5.2.1 Components

RealityEngine supports three levels of total texture depth: 16-, 32- and 48-bit. These are used to store texture information as full-color with transparency (RGBA), full-color (RGB), intensity with transparency (IA), or just intensity (I). Each of these types of texture is available with twelve, eight, or four bits per component.

TABLE 2 Texture Component Options

The 16-bit and 48-bit modes are new functions in the RealityEngine architecture.

The 16-bit mode provides high levels of image quality using full-color, RGBA textures, but with reduced memory usage. Thus textures can be simply constructed by scanning images into the system from color photographs, for example, and then simply applying them to polygons in the database scenario. RealityEngine automatically converts the images to 16-bit textures. No special processing is required to achieve this photorealistic capability, just a good camera, a scanner and RealityEngine.

The 48-bit mode is included to provide 12-bit per component capability for RGBA texture maps. This is some of the highest image quality available on any image generator. The advantage of 12 bits per component is that under low light conditions, banding can sometimes appear on some systems due to the bits in the texture becoming "oversampled". There are just not enough levels to handle the subtle light changes. 12 bits per component increases the number of light levels for each component from 256 to 4096, greatly enhancing image quality under these conditions.

5.2.2 Texture Memory Configuration

RealityEngine provides an extensive 4MBytes of standard, on-line texture memory, stored as two banks of 2MBytes. This is approximately an order of magnitude greater than any prior Silicon Graphics architecture. With the 16 RGBA full-color storage mode, this enables the display of database scenarios with a very high content of photorealistic texture imagery. Different texture types and modes can be mixed together within the memory storage space. Efficient texture storage algorithms ensure that textures are stored sequentially within the memory area, in turn ensuring that all the texture memory is used.

Minimum texture size is 2x2, and maximum is 1024x1024. The system is thus able to store two RGBA full-color 1024x1024 textures. An example may be that a typical simulation scenario may need to use a large number of 128x128 full-color textures. In this scenario, RealityEngine can support 95 MIPmapped, full RGBA and 380 intensity-only 128x128 MIPmapped textures.

Intensity textures on RealityEngine can reference an 8-bit lookup table of 8 bit per component RGBA values to produce full colored and translucent imagery from intensity textures. This further saves memory space and increases the overall texture capacity of the system.

Table 3 explains some of the more commonly used sizes and capacities.

TABLE 3 Texture Map Capacities

RealityEngine supports a new function called 3D Texture. This function enables whole volumes to be stored in texture memory. The volumetric texels can have the same bit depths and functions as 2D texels. Volume textures can also be MIPmapped, creating a series of volumes, each of which has 1/8th the volume of the one above. Some example capacities are described in Table 4:

TABLE 4 3D Texture System Capacity

5.3 Types and Methods

The texture filtering methods on RealityEngine are extensive, providing the highest image quality. The system supports two modes of filtering:

• Non-MIPmapped

• MIPmapped

5.3.1 Non MIPmapped Texture Functions

There are advantages and disadvantages to functions in both categories. The primary advantages of the non-MIPmapped textures are that they use 1/3rd less memory. There are three mapping functions available: bilinear interpolated, point sampled, and bicubic interpolated.

Bilinear interpolation mode looks at the S and T coordinates, finds the nearest four texels, and blends them together to generate the final color value to be applied to the pixel being drawn.

Point sampling offers no real performance advantage over any of the higher quality modes; it is supported to provide backward compatibility with pre-RealityEngine architectures. When point sampling, the system takes the iterated texture coordinates for the current pixel being drawn and samples the specified texture to find the nearest texel to the current pixel's S and T coordinates.

Bicubic interpolation performs a weighted, two-dimensional blend of 16 texels in a 4x4 kernel around the texel sample location specified by the pixel's S and T coordinates. It is used in special circumstances to generate image of unparalleled quality without the use of MIPmapping.

5.3.2 MIPmapped Texture Functions

The primary texture mode of RealityEngine is Trilinear MIPmapping. MIPmapping is a technique that involves the generation of pre-filtered lower resolutions of each texture defined to enable system selection of the texture closest in size to the target polygon. This is the default and fastest texture mode on the system and, while the RealityEngine supports all the modes used on previous systems (point sampled, linear and bilinear), they are intended for backwards compatibility only. There is no performance advantage in using these other modes.

Trilinear Interpolation is one of the highest quality texture functions available and is found on some of the more recent high-end image generators. Trilinear interpolation performs two bilinear interpolations in the two MIPmap levels bordering the size of the polygon being textured, then blends the results of those interpolations for a total of nine blends per pixel textured. This produces images that are very stable under all circumstances yet look very sharp when close. There is no perceptible transition as the textures move relative to the eyepoint.

A further function that is available on the system is Quad-linear 3D MIPmapped texture mode. This is effectively Trilinear interpolation of 3D texture, automatically generating a series of 3D volumes, each 1/8th smaller than the one above. The system interpolates between the eight adjacent pixels in the MIPmap two adjacent volume levels and then blends between the two results, thus achieving a four-way interpolation.

A number of additional advanced texturing techniques are provided on RealityEngine. Many of these can only be found on high-end image generators, these are as follows:

• DetailTexture

  This function is a very powerful feature, increasing the effectiveness of speed, motion, and position cues by providing extra detail automatically where it is needed. DetailTexture blends in a second level of texture on the original as the eyepoint approaches the surface, and multiple pixels cover an area subtended by a single texel. This extra detail level is in fact a completely separate texture map, and is automatically and smoothly blended with the 'host' texture, gradually increasing the detail where the texels are oversampled. Thus, for example, on a road, one texture would be used to depict the road at a distance, with lines, skid marks, and so on, and close to the detail texture would be used to depict the gravel and fine detail.

• Sharp Texture

  Texture is a useful function for depicting detail with the use of very few surfaces, such as for writing on signs; however, when the eyepoint gets very close to such areas, the appearance can become somewhat fuzzy and indistinct. Again, this is because the texels are being "oversampled" and a single texel covers more than one pixel. Under these circumstances, SharpTexture can add a substantial increase in definition to the overall scene without the use of additional texture memory.

• 3D Texture

  This advanced and highly flexible feature can be used to address a series of complex special effects. Texel values are defined in a 3D coordinate system. Textures are then extracted from this volume by defining a 3D plane that intersects this volume. The resulting texture, which is applied to the surface, is the intersection between the volume and the plane. The orientation of the plane is completely user-definable. Sequential reads are blended with each other extremely rapidly. All normal texture attributes function with 3D texture, including full-color RGBA texture filtering functions and volumetric MIPmap capability.

FIGURE 7 Accessing a Texture from a 3D Texture Map

Thus, the displayable result from a 3D texture is not a volume of pixels but a single 2D texture map, extracted from a slice through a volume of texels and applied to a surface. However, it is possible to build up a volume of data by repeatedly slicing through the 3D texture and applying that to a series of "laminate" surfaces that represent the volume. This could be used to simulate clouds or smoke, for example.

Some examples of ways that 3D texture might be used are:

• Texture animations, such as moving people.

• Dynamically changing billboard textures, for instance, a tree billboard could actually change appearance as its angle to the eyepoint changes, even though it remains perpendicular to the viewer.

• Smoke, cloud and dust cloud simulation.

• Multiple levels of detail for textured surfaces. This would enable a large number of images to be blended sequentially under user or simulation control.

  
  

Projected Texture

A new capability on RealityEngine enables non-orthographic texture mapping. This means that a full RGBA texture map can now be obliquely projected onto arbitrary surfaces in a 3D environment. When projecting texture onto texture, this involves a straightforward multipass technique. This is a powerful function enabling a whole series of unique special effects:

• Multiple steerable lights, which are defined by a texture that represents a cross section through the light cone. Radial and axial attenuation are also supported.

• Aircraft shadow projection onto 3D objects such as terrain and buildings.

• Wind effects, such as helicopter rotor wash and wind/wave surface effects for maritime simulations.

• Support of true 3D shadows.

• Dynamic ship's wake projected onto moving waves.

• Projected reflections such as sun glint effects in space applications.

Modulation and Decals

Each texture can be treated in two ways when being applied to a polygon. When operating as a decal, the color of the texture replaces whatever color is already inherant to the polygon. When performing modulation, the texture color is blended with the color and properties of the surface.

Texture Transparency and Contouring

Textures may have full or partial transparency set at any texel location. This means that if the entire outer edge of a uniquely shaped texture (such as a tree) is set transparent, the texture may be placed upon a rectangular polygon, yet appear to have the outline of a tree.

Perspective Correction

Per pixel computations are performed in the Raster Subsystem to correct textures and fog for perspective distortions to insure that no artifacts are introduced into the rendering process. These computations do not impact the system performance.

5.3.3 Texture Performance

The texture fill rates on RealityEngine have been tuned to provide high levels of scene depth complexity at fast frame rates and high image quality.

The texture fill rate for RealityEngine is from 80 to 320MPixels per second for writing of Trilinear MIPmap textured, subsample, anti-aliased, full-color (RGBA), Gouraud shaded, lit, Z-buffered surfaces into the frame buffer.

5.4 Anti-aliasing

Anti-aliasing is a fundamental feature of any true image generation system. Artifacts caused by aliasing cause distraction in a simulation environment, minimizing the level of realism of the system and, potentially, causing negative training.

RealityEngine was designed from the outset to provide high-quality, high-performance subsample anti-aliasing that is easy to use and tunable for different system configurations. Most importantly, anti-aliasing is provided on RealityEngine at no performance penalty. Moreover, anti-aliasing with RealityEngine requires no sorting of data and operates in conjunction with the Z-buffer for hidden surface removal. This is unique at this level of system.

Anti-aliasing is accomplished by retaining subpixel information for all vertices as they are transformed and processed through the pipeline. Each vertex is computed with a subpixel accuracy in an 8x8 subpixel grid. Thus, there are 64 subpixel locations for each pixel rendered. When deciding on how to color a pixel, the system samples the subpixel grid with a certain number of samples per pixel, then determines the pixel coverage based on the number of samples hit.

FIGURE 8 Example Subsample and Subpixel Layout for a Pixel

The following anti-aliasing functions are available on RealityEngine:

• Point Sampled

  When performing point sampling, the system determines for each sample location within the pixel whether that sample is covered by the rendered polygon, vector, or point.

• Area Sampled

  In area sampling, however, the system measures the percentage of the pixel covered by the primitive and translates that into the nearest covered point samples. In both cases, the color and Z values are maintained for each sample, and performance should be the same. Area sampling is suitable for long, thin polygons avoiding breakup.

  
  

5.5 Hidden Surface Removal

Hidden surface removal is performed by a high resolution Z-buffer on RealityEngine. The use of a Z-buffer obviates the need for database sorting and the use of unwieldy binary separating planes. Both of these alternative methods increase the modeling effort and time required to generate a database; they also restrict the overall flexibility of the resulting simulation. The Z-buffer is particularly powerful when a large number of moving models with articulated parts interact with each other, such as an armored vehicle training scenario. A Z-buffer-based system allows free movement of models without any need for concern about occultation. Another area where the Z-buffer is unique is when complex moving geometries intersect with each other, such as the hull of a ship and moving waves, for example.

RealityEngine handles Z-buffering and anti-aliasing simultaneously by storing Z-buffer values for each subsample. This ensures correctly anti-aliased polygon intersections. Resolution of the Z-buffer is configurable up to 32-bit, providing high Z-buffer accuracy for distant objects. RealityEngine supports correct occulting when combining translucency and Z-buffering through the use of alpha coverage masks. RealityEngine also handles polygons and textures through the IRIS Performer environment.

5.6 Polygon Capabilities

5.6.1 Color

Colors may be specified in several different ways. For compatibility, a color index mode is supported where an integer index value points into a fixed size table. More common is the use of fully specified Red, Green, and Blue (RGB) values for each color as it is set. Each component of the RGB color may be defined with 8-bits for 24-bit "true color", or for low light intensity applications, 12-bits per component for 36-bit color and a wider dynamic range.

5.6.2 Smooth Shading

There is no penalty for performing smooth shading on objects rendered with RealityEngine. The Gouraud shading algorithm is utilized to smoothly shade the surface of each polygon using the current lighting model.

When performing Gouraud shading, the Image Engines interpolate between full RGB color values for a given pixel within a polygon to enable smooth pixel to pixel color transitions. Advanced lighting models enable time-of-day or local light sources. This provides for clean, non-faceted rendering of complex objects in real-time, and may be combined with transparency and texture for even more advanced rendering effects.

5.6.3 Color Blending

When multiple occulting surfaces have partial transparency, the Image Engines also perform color blending between each set of surfaces, depending upon the alpha values associated with each vertex, or even pixel (when texture mapping with alpha). These alpha values represent a degree of translucency from 0 to 1 and enable the simulation of windows, cockpit canopies, smoke, clouds, and other effects.

5.6.4 Lighting

Light sources may be colored to allow for effects such as time-of-day lighting, where the color of the light as well as the intensity changes over time. Light sources can be programmed with the following parameters:

• Specular, for highlights and directional effects

• Diffuse, for broader directional effects

• Ambient, for environmental, non-directional effects

• Emission, for self-luminous surfaces, vectors, or points

• Color

• Attenuation with distance

• Local or infinite lights

  
  

Surface Properties

In addition to the four components above, a shininess component may be set for the current lighting model, to handle different surface properties. This component may be changed from object to object to allow for a variety of different surface types in the environment. This property, in addition to the light characteristics and the surface color, may be combined with texture mapping and transparency to provide the highest level of realism.

5.6.5 Atmospheric Effects

A programmable fog/haze function in RealityEngine allows users to set arbitrary fog color, which may then be blended in a depth-dependent fashion with the color of each pixel to be affected by the fog. This can be applied to the whole scene or controlled independently for differeent objects in the scene; for instance, light points may be less attenuated than surfaces in fog. This is sometimes known as per pixel fog. On RealityEngine, it is fully corrcted for perspective distortion.

The fog is computed by means of a programmable function that the user can control by loading the requisite parameters into the system fog table. Alternatively, there are a number of standard exponential functions that can be used.

5.6.6 Polygon Performance

The main focus of RealityEngine for polygon performance is for polygons that are of high image quality, that is, textured, anti-aliased, lit, smooth, shaded, and so forth. This is important for image generation applications, since the majority of the imagery that is being processed by the graphics subsystem is generally of a complex nature.

RealityEngine has been designed to address these requirements in two respects. The first is that the system can transform in excess of 210K textured, anti-aliased, Gouraud shaded, lit, Z-buffered polygons per second. This approaches an order of magnitude faster than previous Silicon Graphics systems. The second is that the graphics subsystem has been designed with considerable elasticity. Two high-capacity FIFO buffers are provided, one between the CPU subsystem and the Geometry Engine and one between the Geometry Engine and the Raster Managers. These effectively allow the pipeline to exhibit considerable parallelism, enabling balanced throughput in the graphics pipeline.

RealityEngine has an innovative and flexible display subsystem capable of scanning the digital frame buffer out to video at varying resolutions and pixel timings. High-speed digital-to-analog converters (DACs) combined with custom circuitry enable software programmability of video output formats without requiring any hardware or PROM changes.

5.7.1 Programmable Video Timing

RealityEngine incorporates advanced circuitry for generating a programmable pixel clock. The pixel clock controls the rate at which the frame buffer is scanned out to a video signal. The standard system runs at a resolution of 1280x1024 pixels, which are output at 60Hz non-interlaced.

5.7.2 Standard Formats

To provide users with as much built-in flexibility as possible, RealityEngine systems are delivered with a broad range of software-selectable video formats, from NTSC to standard 1280x1024 high-resolution, to HDTV.

5.7.3 Composite Output

In addition to the programmable pixel clock, which provides for RGB output at a wide variety of video timings, RealityEngine has standard hardware for the generation of a composite video output from the standard system, to enable users to connect video recorders directly to the system.

5.7.4 Genlock

To assure that RealityEngine graphics subsystems may provide video output that is synchronized with other video sources or pipelines, a standard Genlock capability is provided. Genlock assures that multiple video sources all start scanning out their frames at the same time to get frame-synchronized multi-channel output.

5.7.5 Multichannel Video Output

The optional VideoSplitter/2 board may be utilized for each graphics pipeline to provide for up to six independent channels from a single graphics pipeline. The board takes the digital, ordered pixel output coming off the pixel bus from the XMAP processors of a graphics pipeline and allows the user to specify up to six separate rectangular areas to be sent out of the frame buffer to independent component outputs. The board supports two different, simultaneous video timings, with one timing supporting two outputs and the other supporting four.

Since the VideoSplitter/2 takes the output from the Display Subsystem, it can handle up to 2.6 million pixels in total. This means that a single pipeline can generate, using VideoSplitter/2, two 1280x1024 60Hz displays simultaneously.

The benefits of including host and image generation capabilities in a single system include reduced integration, fast response, and simplified support. RealityEngine provides extensive host capabilities with an advanced, symmetric multiprocessing (SMP) computational subsystem. This subsystem combines parallel CPUs, memory, secondary storage, and I/O to provide the ability to calculate real-time vehicle dynamics, communicate with external communications boards and devices, and access databases in addition to being able to generate visual imagery.

Depending on chassis configuration, RealityEngine can support from one to eight CPUs in a parallel processing environment. Three RISC processor types are available: R3000 (33MHz), R4000 in single processor configurations, and R3000 (40MHz) in multiprocessor configurations. Table 5 summarizes the CPU configurations and performance available.

TABLE 5 RealityEngine: CPU configurations and Performance

Simulation applications often lend themselves naturally to multiprocessing. Typically, multiple simulations operate concurrently (as in flight dynamics, engine model, and landing model), and results from these calculations are required simultaneously for determination of the update of vehicle position. RealityEngine multiprocessing can be implemented at many levels, including the job, process, and procedure levels. Multiprocessing tools and parallel compilers assist in the development of real-time multiprocessing applications.

6.3.1 REACT

Silicon Graphics' IRIX operating system is based upon a POSIX-compliant version of UNIX System V3. It has, however, required special modifications to support multiple processors, a concept not covered by standard UNIX. These special functions at the heart of IRIX have been combined under the banner of REACT, the RealityEngine Time Access Technology kernel.

REACT offers a set of system calls that enable real-time operation of systems running IRIX. Because real-time functionality is key to the operation of simulators, REACT acts as the core of the system's host capability. REACT provides deterministic response to interrupts and deterministic dispatch latency.

Some of the key features of REACT include:

• Standard UNIX with deterministic response

• Fast total interrupt response: < 200 microseconds

• Shared-memory symmetric multiprocessing with full user control over system resources

• Highly productive software development environment

• High-performance networking

  
  

6.3.2 Deterministic Response

UNIX was originally designed to distribute CPU time and other system resources equally among users of a time-sharing system. As a result, predicting precisely when any event will occur in a generic UNIX system is impossible. IRIX with REACT includes the following extensions to generic UNIX which, together, result in a fully deterministic system suitable for real-time applications:

• Interruptable Kernel

• Precise process Priority Control

• Non-degrading Priority

• Locking Memory Pages

• Processor Isolation

  
  

One of the benefits of a deterministic system that supports a full UNIX-based operating system is a rich development environment that enables rapid generation of tuned simulation applications on the target system, not on a dissimilar, remote machine. This reduces the cost of the installation and ensures that the application is developed in the context of the final operating environment. Some of the tools available in this environment are:

• Wide range of compilers

• Multiprocessing tools

• IRIS Graphics Library (GL), an extensive 3D graphics library

• Image Processing Library

• Graphically based profiling and debugging tools

• CASEVision WorkShop, a CASE development environment

• IRIS Performer, a simulation-specific development and run-time environment

  
  

As low-cost simulation applications evolve, two key elements are becoming increasingly apparent:

• There is a demand for deterministic, high image quality and performance at low cost

• The image generation system should be flexible, evolvable, and capable of handling special effects

The combination of RealityEngine and IRIS Performer presents a unique opportunity to provide both of these elements for the first time in the low-cost visuals market. The goal is to provide developers with software tools that enable them to create high-performance simulation applications quickly and easily on Silicon Graphics systems. IRIS Performer reduces the time required by developers to create a new generation of innovative, low-cost, real-time, deterministic simulation systems.

IRIS Performer offers functionality in a number of key areas:

• High Performance

  IRIS Performer maximizes image generation throughput, using multiple processor task partitioning, efficient database traversal, and highly optimized polygon rendering.

• Rapid Development

  IRIS Performer provides an easy-to-use interface that reduces user application development time and reduces the need to possess intimate knowledge of the hardware platform. This permits developers to focus attention on the specific issues that make their simulations unique.

• Rich Functionality

  IRIS Performer implements advanced image generation features required in sophisticated out-the-window simulation applications. These features include frame synchronization, system load management, atmospheric effects, raster light points, and spatial inquiries.

• Enhanced Portability

  Using IRIS Performer, applications are developed around a fully supported, simulation-specific user interface that will evolve over time and enable simple upgrades of simulation systems to future hardware architectures.

• The Open Architecture Image Generator

  IRIS Performer is not a closed book. It is fully extensible and provides an environment that makes the addition of new functions and effects a simple exercise. This enables the image generator system to be adapted readily to a variety of applications as well as being capable of being evolved to meet future requirements.

  
  

IRIS Performer is a toolkit that provides libraries for obtaining optimal graphics performance and for creating visual simulation applications. It consists of two libraries: the Rapid Rendering Library and the Image Generation Library.

7.2.1 The Rapid Rendering Library

This is a low level library that provides high speed rendering functions, state control, and other machine oriented functions.

The Rapid Rendering Library consists of a number of facilities required in most simulation and real-time graphics applications:

• High-speed rendering functions (GeoData)

• State managed rendering (GeoState)

• State management and mode control

• Display list rendering

• Extensive set of math routines

• Intersections

• Color tables

• Asynchronous file I/O

• Memory allocation

• High speed clock

  
  

7.2.2 The Image Generation Library

This higher-level library, built on top of the Rapid Rendering Library, provides an environment for creating, updating, and rendering a scene database at fixed frame rates. It is a rapid prototyping environment that utilizes the Rapid Rendering Library functions to create a multiprocessing, automated database rendering system. The primary functions are:

• Hierarchical scene graph

• Multiprocessing (parallel simulation, cull and draw processes)

• Overload and frame management

• Level-of-detail model management

• Rapid culling to the viewing frustrum

• Intersection testing

• Dynamic coordinate systems

The following subsections describe the most important IRIS Performer functions.

7.3.1 Database Structure and Traversal

Traversal processing for complex hierarchical databases is the major function of the Image Generation Library. It is the series of steps required to transform a database and viewpoint definition into a Rapid Rendering Library display list suitable for rendering.

The traversal processor constructs a special display list in the form supported by the Rapid Rendering Library. Once the display list is created, it is made available to the drawing functions of the Rapid Rendering Library for processing through the IRIS Geometry Pipeline.

7.3.2 Scene Culling

Many Simulated environments define a database that is much larger than the maximum possible visual extent. Scenes are culled to eliminate geometry not included in the observer's field of view.

7.3.3 Level-of-Detail Management

Part of the real-time database traversal processing is the selection of proper level-of-detail for multiple-representation models. Such models exist as a series of progressively more elaborate models representing increasingly finer model details. The traversal task selects the appropriate model or model pair for rendering based on a number of factors, which include:

• object range

• simulation field-of-view

• display surface size and resolution

• design eye-point to display surface range

  
  

7.3.4 System Load Management

Typically, simulation databases have uneven polygon density, which requires control functions that maintain a steady frame rate. The Image Generation library is designed to use a series of methods to anticipate and smooth the effects of the dynamic nature of system load in order to maintain a constant image update rate. The image generation library uses the concept of stress as a measure of system load. Stress measures the portion of simulation frame time required to process a scene, through both the traversal and rendering stages. This is then used to determine the levels of detail required to maintain the desired frame rate in the scene.

7.3.5 Database Query

The Image Generation Library supports host inquiries regarding the active database during real-time simulation activities. These inquiries are spatial searches that:

• detect collisions

• determine height above terrain

• calculate ranges to nearest obstruction

• verify object intervisibility

  
  

7.3.6 Environmental Control

The earth/sky model provides the backdrop upon which the application may draw a visual scene. It may be used in place of a "clear screen" function and has several user selectable features:

• earth/sky color, texture, and selection

• horizon model

• fog and haze depth

7.3.7 Visual Effects

Weather effects provide effective visual simulation of a number of natural phenomena that have been tuned for both performance and image quality. The weather effects provided by the image generation library consist of fog, haze, cloud layers, and atmospheric layer transitions.

The Image Generation Library treats light points, which represent point light sources, with special attention to visual simulation needs. Color, intensity, shape, directionality, and pattern can be defined to control their appearance. Lights can be steady, flashing, rotating, and strobing.

The sample simulation application provides a flexible, out-the-window simulation application that demonstrates IRIS Performer's power and flexibility. This sample application is layered above the Image Generation Library and serves as an example of its programming model and interfaces. It consists of source code implementing IRIS Performer and a generic database.

RealityEngine is a series of products that represent the high end of a very broad product range of computer systems from Silicon Graphics. With systems that range from desktop personal computers to high-performance 3D workstations to supercomputer computational servers. The Silicon Graphics product line offers solutions to the whole range of simulation applications in addition to image generation capabilities. A key advantage is that all Silicon Graphics systems are binary compatible, which means that applications can be developed on one platform and easily moved to another. This increases overall flexibility and reduces development time.

One of the areas that is key to the entire image generation process is database modeling. It became apparent to visual systems suppliers some time ago that an interactive 3D capability for database modeling vastly improved the quality of the database, reduced database construction time and provided the end customer with the ability to maintain and evolve the databases on the simulator.

Silicon Graphics systems provide not only the interactive 3D capability at low cost, but also the ability to edit complex textured scenes in real time. As database requirements escalate and low-cost visual systems capable of handling large quantities of texture information become available, the emphasis of much of the database modeling will be in the modeling of texture. It is important not only to be able to view textures themselves but to view the whole scene in real time. RealityEngine provides this capability by combining image generation and database modeling capability in one system.

Other applications that the Silicon Graphics product range is frequently used for are:

• Instrument prototyping and simulation

• Mission planning, rehearsal and simulation

• Host computational systems

• Instructor Operating Stations

• Air Traffic Control

• C3I applications

• Computer Based Training (CBT)

There is a wealth of third party software applications for Silicon Graphics systems available in these areas, enabling rapid and cost effective turnkey solutions to simulation problems.

• A flexible image generation system for low-cost flight, ground, space, maritime, and virtual reality applications

  
  

• 1 to 4 high-resolution (1280x1024) channels per system

• Up to 12 independent channels per system with individual eyepoints

• Up to 5.2 million, textured, displayable pixels output from a system

• Up to 320 million anti-aliased, trilinear, MIPmap textured Z-buffered pixels per second fill rate per graphics pipeline

• User-definable display line rates

• Separate composite video output standard

  
  

• Up to 32 bit Z-buffer fully integrated with anti-aliasing

• Coplanar surfaces

• Texture decal support

  
  

• Over 7000 polygons per pipeline at 30Hz [ie. in excess of 210K/sec]

• Polygons textured, anti-aliased, and Z-buffered

  
  

• Photomap texture

• 4MBytes texture capacity standard

• Programmable texture map sizes from 2x2 to 1024x1024 texels

• Trilinear MIPmap texture capability

• 3D texture

• DetailTexture

• SharpTexture

• Up to 380 high-resolution (128x128) MIPmapped textures

• 4 to 48 bits per texel

• Lighting and smooth shading blended with texture

• Dynamic texture projection

• Environment mapped texture

  
  

• Up to 16 subsample anti-aliasing

• 8 or 12 bits per color component

• Lighting, shading, reflection, Z-buffering, anti-aliasing, and translucency all combinable on same surface

  
  

• Database traversal, culling, and rendering

• Fade level-of-detail

• Overload management

• Frame rate control

  
  

• Height above terrain

• Collision detection

• Range finding

• Line of sight

  
  

• Environment mapping

• Steerable landing lights

• Shadow casting

• Texture animation

• Articulation and geometry animation

• Horizon glow

• Support for extended special effects

• Directional shading and lighting

• 8 Configurable light sources, material properties control

• Full color interpolation on surfaces

• Lighting functions definable: ambience, diffusion, specularity, shininess, emissivity, position, and color

  
  

• Over 100 simultaneous moving models (6 DOF)

• All models Z-buffered and anti-aliased at subpixel level

  
  

• Fog, haze, clouds

• Tunable fog functions

• Time of day

  
  

• 83ms at 30Hz update and 60Hz refresh

  
  

• Standard 21 inch multisync monitor

• Digital video capability

• Selectable display from VGA to HDTV

• Genlock

• Independent NTSC or PAL video output standard

• Custom line rates

  
  

• Up to 4096 levels of translucency

• Alpha to coverage function allows translucency, Z-buffering, and anti-aliasing simultaneously

  
  

• IRIS Performer simulation development library enables flexible and rapid application development

• Image Processing library

• Debug and performance tuning tools

• Multiprocessing tools

  
  

• Raster based light point support

• Brightness and size vary with distance

• Independent light point fogging

• 3:1 trade off with polygons

• Directional lights

• Strobes, beacons, flashing, and rotating lights

  
  

• Up to 8 multiprocessing RISC CPUs

• 30 to 286 MIPS and 5 to 70 MFLOPS

• REACT real-time system kernel

• Interrupt latency of <200 microseconds

• 4 to 6 VME slots

• High-speed disk and peripheral I/O support

• Up to 256MBytes of system memory

• ADA language

• Secure O/S. Trusted IRIX (Security level B1) available

  
  

• Multiple color maps enable support for different sensor types

• Custom outputs configurable to suit display

  
  

• Optional digital audio board

• Programmable audio library

For more information please call
US: 1 800 800 SGI 1 (7441)
UK: 0 800 440 440
Australia: 008 802 677

Corporate Office
2011 N. Shoreline Boulevard
Mountain View, CA 94043

Copyright 1992, Silicon Graphics, Inc. All rights reserved.

Silicon Graphics, the Silicon Graphics logo, and IRIS are registered trademarks, and RealityEngine, IRIS Performer, Geometry Engine, VideoSplitter/2, SkyWriter, POWER Series, REACT, IRIS Graphics Library, Crimson, IRIX, GL, CaseVision, Rapid Rendering Library, Image Generation Library and Geometry Pipeline are trademarks of Silicon Graphics, Inc.

MIPS is a registered trademark, and MIPS R3000 and R4000 are trademarks of MIPS Computer Systems. UNIX is a registered trademark of AT&T Bell Laboratories. All other registered and unregistered trademarks are the properties of their respective holders.

Specifications are subject to change without notice.

[typed up by hand from the original 31 page document, from 8th to 13th of May 1998, by Ian Mapleson]