OpenSkies Architecture

OpenSkies is a simulation system designed with a modular architecture. This means that any of its components can be replaced with custom versions to achieve the desired functionality. This is only one of the key technologies in the OpenSkies architecture, however.

• Modular architecture
  - Modular architecture is implemented using dynamically loaded libraries (DLLs), code modules that are loaded at runtime. There is a well defined interface between the main executable and each of the DLLs. As long as a new DLL follows this interface, it can be swapped for an existing module and it will be loaded at runtime to provide custom code to the simulation. DLLs can be used to create a new vehicle 3D model, new sounds, new terrain, etc.

  The following diagram is a visual representation of the OpenSkies architecture:

• Realistic Terrain and Environment
  - OpenSkies provides an accurate virtual representation of the real world including terrain and landmarks extracted from real geological and cartographic databases. Cultural features and details such as urban areas, forests, and roads are represented graphically in 3D. Using OpenSkies environment tools, you can also create your own custom worlds to suit your specific needs. Want to fly over the Grand Canyon? Grab the publicly available data from the US Geological Survey's web site, run it through our loader, and voila, the Grand Canyon is imported into OpenSkies, complete with accurate roads and terrain types. OpenSkies can even import your favorite SCASM format airports! As you fly over the different terrain, you can call up the moving map display to show your current location plotted on a scanned map as well. You can define weather cells and cloud layers to further tailor your simulation experience.
• Multi-User Networking
  - Networking is an essential part of OpenSkies as well. As a truly distributed simulation system, each of the connected PCs runs a separate piece of the simulation. This system takes advantage of the latest advance in military simulation networking, the High Level Architecture (HLA). This standard networking system was developed to foster interoperability between simulations. Using the HLA standard, a flight simulator can participate with different types of simulators, such as attacking ground vehicles or even landing on aircraft carriers. This interoperability leads to unprecedented capabilities for constructing simulations from custom pieces.
• Scenario Editing and Recording
  - OpenSkies also includes a scenario scripting capability suitable for designing and executing specific missions. Mission recording and playback is also included to allow post-exercise evaluation and review.
• SEDRIS
  - SEDRIS is a data interchange mechanism designed to facilitate the interchange of synthetic environments between simulators. For example, say a tank simulator needs to participate in a simulation with an aircraft simulator. For a fair fight, these simulators need to agree on a common representation of the playing field. If there is no "ground truth", then the terrain and objects may end up in slightly different places for each simulator. This leads to problems when the tank driver thinks he is hiding inside a building, but the aircraft pilot sees the building in a slightly different location which may not be providing the concealment that the tank driver assumes. If the aircraft pilot can see the tank when the tank driver thinks he in inside a building, there will be a problem. SEDRIS addresses this problem by providing a lossless data interchange mechanism defining a data model with standard access methods (API). Using this API, different simulations can use a common environment database and extract the data into whatever format they need. The tank simulation can extract the data into its own proprietary format and the aircraft simulator can do the same. Because SEDRIS is a lossless interchange mechanism, the data will remain accurate for both simulator formats. Since both simulators extracted the data from the same "ground truth" database, the buildings and objects will be represented consistently in both simulators, allowing a fair fight. OpenSkies supports the SEDRIS API to make our environments available to other applications. By supporting this standard interchange mechanism, we are further opening the doors of expandability.
• Object and Vehicle Creation
  - The OpenSkies software is designed to be as open as possible, and can be modified by users with varying levels of programming ability. With no programming experience, general users will still be able to create fully functional land, sea, and air vehicles by using their favorite VRML authoring tool and OpenSkies' pre-built vehicle models. The advanced programmer can write additional code modules and easily create custom objects for OpenSkies using the full functionality of OpenGL and C/C++.

  We used this system to develop simulations of a T-34 Mentor single engine aircraft and a TH-57 Bell Ranger helicopter. We developed these modules under government contract for use in training US Naval aviators and provide the OpenSkies aircraft modules to the public to enjoy and use in developing other simulations. The collection of modules that comprise these aircraft include graphical models written in OpenGL, parameterized flight models, panel models using real photography, and force feedback based on the flight model rather than canned special effects.

  To populate the environment, OpenSkies supports the creation of custom dynamically loaded libraries (DLLs) that describe behavior and appearance of all sim objects. This gives the user the power to create anything from a spinning windmill to an artificial intelligence entity flying in a holding pattern. The possibilities are endless when the graphics are based on OpenGL and the behavior code is specified in C++. Non-programming users can easily add custom simulation modules developed by others in the community and posted to the OpenSkies site, supporting a growing base of content.