Hierarchical task network prototyping in Unity3D

Abstract

The Combined Arms Analysis Tool for the 21st Century, or COMBATXXI, is the primary analytical combat simulation model in use by the Marine Corps' Operations Analysis Division (OAD) and the Army's Training and Doctrine (TRADOC) Analysis Center for weapon system and force effectiveness analysis. The bottleneck in the COMBATXXI scenario production process is the behavior development process. Analytically useful scenarios demand complex and dynamic behaviors that react to the unique circumstances of the simulation's current state. Hierarchical Task Networks (HTN) are the state-of-the-art methodology in COMBATXXI used to describe dynamic behaviors. Although HTNs decrease the scenario development time, they are difficult to conceptualize, validate, and troubleshoot. The long iteration cycle is due, in part, to the complex development environment, the necessity of a large simulated infrastructure to test behaviors, and an inability to visually debug. Here we present a solution for prototyping HTNs by extending an existing commercial implementation of Behavior Trees within the Unity3D game engine prior to building the HTN in COMBATXXI. Existing HTNs were emulated within this prototyping environment to test transferability of the behaviors, and new HTNs were prototyped in Unity3d prior to being built in COMBATXXI as a proof of concept. Prototyping HTNs in a 3D development environment may prove useful by reducing the iteration time and improving the overall quality of the behaviors. The interactive nature of Unity3d reduces the iteration time, and the ability to rapidly test many different cases improves the quality of the behaviors.