CTDB 3D Viewer EditorRichard Pater [email protected] Hsieh [email protected] Barry SilvermanAbstract Compact terrain database (CTDB) is a complex terrain database format widely used by the military in training simulations. Currently, many CTDB viewers are made specifically to render the terrain and object models 3 dimensionally in high resolution. These programs focus on editing capabilities that either change the way the terrain is presented in 3D or convert the loaded database to a different output format. Unfortunately, these programs do not provide a simple interface for adding markups, additional attributes for a terrain feature that a simulation system may wish to use, to the terrain features. In addition, these viewers tend to be overly complicated, unwieldy, and expensive. The software we are building will be a user-friendly 3D viewer of the CTDB format. Our software will implement a simple and intuitive GUI to make 3D viewing and exploring extremely easy for a user. Beyond what CTDB viewers currently provide, our software will support editing and will interface with other related software. Editing will involve modifying existing attributes or adding new markups to objects in the environment.Related Work The CTDB format has been widely used by the military in virtual training exercises. This extensive database contains the physical and abstract features of terrain including buildings, roads, rivers, and terrain skin as well as attributes such as soil type or bathymetry (depth of water). The military uses this database format to realistically map and simulate buildings, roads, political boundaries, and other terrain features. CTDB viewers are programs that translate the database into full-scale, accurate representations of the environment, most commonly in 3D.There are a few commercial CTDB viewers that are on the market today, and they are usually acquired by purchasing a license. TerraTools, created by TerraSim, Inc., is a modeling program that creates a 3D environment from a CTDB or other terrain database format using OpenGL.This is similar in some ways to our software, but obtaining one license for the TerraTools package costs $23,000. A price this high makes the software prohibitively expensive for use in the types of applications for which our system will be designed. Terrain Experts, Inc. (TERREX) also has a CTDB viewer program called TerraViz which models the environment extracted from a CTDB in 3D. This program, however, has extremely limited editing capabilities and is primarily a simple viewer. They charge a more reasonable amount for this software, $1,500 per license, but it does not have the editing capabilities that our system has. A major limitation to these commercial programs is that they do not contain programming that allows the type of editing that our system provides. Our software has the capability to add attributes or markups that can be used as descriptions, properties, or values. Importantly, markups can be used to form relationships between agents and the virtual environment in a simulation. A psychologist, JJ Gibson proposed that features in the environment (terrain, types of buildings, water, etc.) consist of affordances (possibilities for action) which provide necessaryclues toward perception. According to “Affordance Theory for Improving the Rapid Generation, Composability, and Reusability of Synthetic Agents and Objects,” a virtual world based on affordances interacts with agents, leading to perception, sensation, and action. An example of this theory in use in a real system is the computer game, The Sims. The Sims allows simulated characters (sims, the agents in the theory) to perceive the virtual world and act out according to affordances in the environment. For example, a television set affords watching or playing videos. Sims have certain tanks such as energy, hunger, and entertainment as well as others. When the entertainment tank is low, a sim will seek objects in the environment that can fill this tank, such as the television set. By walking toward the television set and turning it on, a transaction takes place. The television will fill the entertainment tank but the sim’s energy tank will decrease. The markups that our system adds to the CTDB will be used in a way similar to the markups used in The Sims, but they will be used primarily by PMFServ agents, at least at first. PMFServ is a program that uses PMFs, or Performance Moderator Functions, to realistically simulate agents in an interactive environment. An agent has a large number of PMFs to regulate different aspects of behavior. Example PMFs include stress, personality, perception, social processes, and cognition. At the moment, PMFServ has no way to grab markups out of a CTDB or add markups to a CTDB that it needs. Our project is a free alternative to existing CTDB viewers on the market. The fact that our software is freeware gives it a distinctive edge over expensive existing commercial products.Our editor is also able to add markups to the CTDB database, which can be used in different ways. They can be used to describe physical location, name, or ownership as well as to describe affordances that will be useful for interactions between simulated agents and the virtual worlddescribed by the CTDB. They are also useful in defining legal agent movement within the world by providing information such as whether or not an agent can walk on or through a particular location. Another property of markups is that they can aid navigation by providing endpoints for decision based movements. For example, a hungry agent might walk down a road and into a restaurant because the markup of the restaurant tells the agent that he can acquire food there.Through the XML-RPC interface that can be used by PMFServ, our viewer/editor can be used to populate the simulated world in PMFServ with objects and affordances leading to more complex and accurate simulated behaviors for the agents. Technical Approach The system that we built works by importing a CTDB tile and using the information contained within the database to draw a 3D representation of the terrain. CTDBs store terrain features as collections of vertices given in geocentric locations. Different types of features also contain additional attributes specific to those features. Buildings, for example, contain a collection of roof elevations that correspond to the vertices of the