Ready, Set, GO
The MultiGen GO runtime solution

Written by Tom Dowgiallo
MultiGen Inc.

November 1997

MultiGen GO™ is a runtime image generator (IG) application for Silicon Graphics workstations that delivers the best value in the marketplace for its combination of price and performance. GO provides an extensive visual simulation feature set, including a large area database manager that allows continuous flight over vast areas through database paging. Ready to use without further development effort, GO reduces development time and cost, while delivering high-quality, interactive, real-time display.

Powerful, feature-rich, and ready-to-go, MultiGen GO provides a turnkey runtime solution for flight and ground warfare simulation. In addition, because GO is so cost-effective, it is ideal for many special-purpose uses, such as previewing simulations before porting to the target simulator, trying out scenarios in a laboratory environment, conducting flight-test and missile-launch rehearsals, rapid prototyping, validating onboard components, and viewing mission playbacks.

With the addition of GO to the growing MultiGen product lineup, we are meeting customer needs for an integrated solution for realtime 3D modeling and display.

The integrated solution

With MultiGen's integrated solution, you get everything you need from a single source to model and display interactive visual simulations. Elements of the complete MultiGen solution include

ò OpenFlight, the industry standard real-time 3D scene description database defined and supported by MultiGen, Inc.

ò OpenFlight APIs, providing a quick and easy means of accessing, extending, and customizing OpenFlight databases

ò MultiGen 3D modeling software, a comprehensive set of general-purpose synthetic environment 3D modeling tools that enhance productivity and promote innovation in visual simulation

ò MultiGen GO, a high-performance, ready-to-use image generator application

ò MultiGen Solution Center, offering indepth, customized training, consulting, and development expertise to make realtime 3D development easier

By incorporating the GO runtime solution with our industry-standard modeling tools, MultiGen provides the assurance of compatibility. Our products are designed and tested to work together cohesively. In addition, MultiGen stands behind the total solution. Customers can depend on quick, responsive support from the recognized authority in visual simulation.

Easy to set up and get going

MultiGen GO is a ready-to-use runtime IG application. It processes OpenFlight databases created and edited with MultiGen 3D modeling tools for realtime display. It executes on a variety SGI workstations, from O2 to Onyx2 InfiniteReality systems and is compatible with the IRIX 6.2 (or higher) operating system. GO is table-driven by a host simulation application that may run on the same computer as GO, using shared memory, or on a separate computer, communicating through reflective memory (VMIVME-5550 board) or ethernet.

GO is an Iris Performer application that uses either IRIS GL or OPEN GL and IRIX system calls. GO gives immediate access to the full feature set of the Performer visual simulation tool kit. No special programming is required. As a result, developers are more productive, more quickly. And because effort stays focused on creating the simulation, not on programming a proprietary image generator application or coding hardware hooks, development costs are significantly reduced. Simply load the MultiGen GO CD the SGI workstation, and you are ready to go.

For integrated simulator operation, the host computer sets parameters and flags in the interface table, and GO uses them to drive the IG. For stand-alone operation, a sample host program is provided to drive GO features through keyboard and mouse control.

Ownship simulation

The main viewing point of the visual database is the "ownship," which is the view out of the window of the aircraft or other vehicle as it moves around the database. GO controls the view produced from the ownship position.

Position prediction. Position prediction is one way MultiGen GO maintains high performance. GO predicts ownship position by extrapolating based on information about velocity and acceleration. This capability compensates for data transport delay that results in latency between the calculation and communication of position by the host and display by the IG. GO also predicts ownship position when data is not available from the host due to asynchronous communication between the host and the IG. Data is smoothed, creating a continuous simulation experience.

Collision detection. GO detects collisions by continuously checking three lines for intersection with database objects, using either default lines or lines passed dynamically from the host.

Terrain height detection. GO continuously calculates the height of terrain under the ownship, which is essential for a realistic simulation of landing.

Landing gear control. GO controls the state of three landing gear and provides feedback to the host to simulate the jolt and motion of landing and the ground texture below the wheels.

Light controls. Two independent light sources can be used to simulate landing lights, taxi lights, or spot lights attached to the ownship.

Ownship model. Though the ownship normally isn't modeled in the visual database, it can be an important part of the scene. GO can display a model of the ownship as it would appear out of the window, obstructing other parts of the scene, or as it would appear viewed from a helmet mounted display with a 180-degree field of view.

Sensor simulation

In addition to the ownship view, GO allows two other independently controlled view points, such as co-pilot or navigator viewpoints or sensor visualizations. Sensors can be positioned and moved freely through the database, just like the ownship, or they can be attached to the ownship. GO supports a variety of sensor simulations, including infrared sensors, low-light TV, and night vision goggles.

GO provides extensive control over the imagery produced to create realistic sensor effects. Sensor views can be enhanced with the following special effects:

Gray scale bar. A graduated gray scale bar can be displayed in the sensor view.

Automatic contrast enhancement. When enabled, this feature filters the gray scale sensor view so that the darkest shades become black and the lightest become white.

Image fade. This feature fades the image on the sensor display to black.

White hot/black hot. By default, the hottest objects are displayed as white, while colder objects are displayed in darker shades of gray to black. However, this continuum of display can be inverted so that the hottest objects are black and coldest are white.

Focus. The focus effect blurs the sensor image, on a sliding scale from in-focus to completely out of focus.

Brightness and contrast. Brightness and contrast of the sensor image can be adjusted.

Image scale. The image being generated can be reduced in sized for sensor display.

Visibility control. Visibility in the scene can be controlled independently for the different sensor views.

Extensive feature set

MultiGen GO gives instant access to an extensive feature set with all the essentials for creating effective visual simulations. Especially well suited for flight simulation, GO's rich feature set includes the following wide range of environmental effects:

The GO feature set includes a comprehensive selection of environmental effects for realism.

GO automatically controls ambient and diffuse light, color of the sky, horizon glow, and the position of the sun or moon, based on the time-of-day supplied by the host. Alternatively, control of natural illumination can be turned over to the host.

Weather effects include clear sky, haze, patchy fog, fog, patchy cloud, and overcast. Transition layers from one weather effect to another are adjustable.

Stars are simulated in night scenes when the sky is clear. The star database holds up to 2,000 stars.

GO allows up to six storm cells simultaneously in the scene. Storm intensity, cloud size, heading, and vertical extent can be controlled. The IG automatically determines the ownship's range to all storm cells in the simulation. Simulated lightning strikes on the ownship are represented by a white flash over the scene.

Control of lightpoints

GO provides individual brightness and color controls for realistic lightpoints. Fixed lights and lightpoints on moving models brighten or fade accurately with distance and with environmental conditions, such as fog or haze and time of day. User-definable and controllable lights supported by GO include VASIs, rotating beacons, running rabbits, and strobes, as well as airfield runway, taxiway, and approach lights.

Lightpoint control is available on all channels for accurate out-the-window and sensor visualization. For example, lightpoints can be used to model infrared heatpoints.

A battery of special effects

The GO feature set includes special effects that can be inserted into the scene for realism and training value. These special effects include the following:

ò Bomb impact marker, that takes the form of large emissive shapes locating where weapons have hit.

ò Explosion, appearing as an orange-red expanding cloud.

ò Missile launch, providing a light flash on the side of the ownship from which a missile has been fired.

ò Ground missile launch, displayed as a flash and smoke cloud when a missile is fired from the ground.

ò Missile plume, simulating the trail of a missile in flight.

ò Tracer burst, simulating tracer bullets being fired from anti-aircraft artillery

ò Muzzle flash, that provides a flash at the end of gun barrels as they are fired

ò Fire, to simulate burning

ò Flare, that consists of the flare itself and a localized light source illuminating the terrain and other objects as the flare moves

ò Smoke, that appears as a column of smoke rising

Moving models

MultiGen GO accommodates up to 100 dynamic models and articulations in the scene. GO uses position-smoothing to minimize jerkiness in motion when the host is updating the positions of moving models slower than the frame rate of the IG. Other models may also be located relative to moving models or to the ownship, such as wing weapons.

Large area database management

MultiGen GO delivers high performance without sacrificing fidelity. For example, GO running on an Onyx2 four-processor workstation easily managed the display of image and special effects at real-time frame rates for a large-scale Air Force pilot-training exercise. Developed as a showcase demonstration for the Air Force's 50th anniversary, the simulation encompassed nearly a 1,000-square-mile area of Alaskan wilderness. The visual database included 1.3 million trees; detailed textures of snow, rock, and shadow patterns on mountain slopes; and models of the airfield runways, landing strips, and buildings. Atmospheric effects were rendered faithfully. Snow turned pink at sunset. Moonlight, fog, and daylight visibility effects were accurately simulated.

GO uses visual databases created and edited with MultiGen 3D modeling software. The GO Database Converter automatically compiles OpenFlight databases into a Fast File Format that is faster and more efficient to load for continuous database paging. The GO Large-Area Database Manager (LADBM) manages database paging to maintain a constant load on the CPU, resulting in consistent, optimum performance. The LADBM moves scene content in and out of memory dynamically, always keeping the ownship at the center of the active database. In this way, the size and extent of visual database is not constrained by system memory size.

GO compensates for gaps in the visual database, where source data is not available, by providing a world map and defaulting to generic sea or generic land, as appropriate.

The LADBM supports both flat and round earth models, eliminating the need for conversions, which can introduce errors. Dynamically relocatable origins prevent anomalies and ensure accuracy over long traversals.

Because of GO's efficient LADBM, you can

ò Create larger and larger visual simulation exercises without compromising accuracy of detail

ò Get maximum performance from your host system

ò Achieve disruption-free flight

MultiGen GO: a superior value

In power, range of features, and ease of use, MultiGen GO is the most cost-effective alternative on the market. A complete, turnkey runtime solution, it executes, as-is, on industry standard Silicon Graphics workstations, saving development effort and cost. It offers the essential feature set and high performance for effective realtime simulations. You don't have to choose between detail, world size, and performance. With cost-effective GO, you get an optimum balance of them all.

For more information

GO is a demonstration of MultiGen's continuing commitment to meeting the full range of needs--from modeling to display--in the visual simulation market place. To learn more about MultiGen GO or the other elements of the MultiGen integrated solution, please contact Chantelle Shaban at (Tel) 408-556-2616 or (Fax) 408-261-4101, or email chantelle@multigen.com.

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