Tactical AI in Real Time

1. Tactical AI in Real Time Supervisor: Aleks Jakulin Crew: Damir Arh, Matija Jekovec, Mitja Luštrek Gregor Leban, Martin Žnidaršič, Uroš Čibej Translation: A. Jakulin

2. Task • real-time strategy • objective: survive • based on physical simulation • computer assists the player (intelligence amplification instead of artificial intelligence) • teams of AI units • the player does not control individual unit’s behavior • units perform team-allocated duties

3. Program Structure1/2 • Two separate applications: • server • client • Client: • graphics • user interface • server connection

4. Server: communication with clients physics pathfinding Hierarchical AI Strategic layer Team Unit (soldier) Program Structure2/2

5. PhysicalModel 1/3 • Terrain: • 2D map • passable / impassable kvadratki • continuous space and time • map fully revealed to AI • enemies only seen if at least one of units has visual contact

6. PhysicalModel 2/3 • Unit properties: • movement: • poses: walking, sneaking, crawling • movement speed dependent on orientation and health • separate movement direction and orientation • 3 shooting modes • health-, speed- and orientation dependent • view angle depends on speed of movement(F-01)

7. PhysicalModel 3/3 • Collision detection: • unit collisions • bullet collisions • Raycasting: • map intersections • object intersections

8. Visibility Graph • `expand’ the walls for unit radius • visibility graph nodes are convex corners • mutually visible corners are connected • before pathfinding, insert start and goal points in the graph • search with A* (F-02), heuristics(F-03)

9. “Boids” • Basic rules: • a unit tries to move towards the center of the team • a unit tries to keep a minimum distance from walls and objects • try to match team speed • These Rules are too local!

10. Teams • Units in different teams are separate from one another(F-04) • Significance: • hierarchical pathfinding • minimize team exposure • maximize team cohesion • formations

11. Teams: Pathfinding • Player sets the goal point, team adjusts individual unit movement given the requirements(F-05) • Pathfinding requirements: • safety • accessibility • proximity to goal • team cohesion

12. Teams: Exposure • Seek proximity of walls and corners, where the ratio between the visible `covered’ terrain and `uncovered’ terrain is minimal. • Note: we ignore mobility

13. Teams: Cohesion • It is more desirable for units of a team to remain close and cover the terrain together. (F-06) • Note: in reality it’s the ease of signaling and directed firepower that matter.

14. Finite State Machine • Controls the units of a team • simple – well-known concept • readable – states are clearly separated • extensible – simple to add new states and transitions • adjustable – we choose to do whatever we please in a given state • We have state-dependent weights, adjusting the boids model.

15. Mitja Luštrek, Damir Arh, Matija Jekovec MDM FSM(F-07) move init advance idle attack Seek cover retreat prone

16. Maintaining Terrain Visibility • During movement, the team leader is looking left and right, if there is no wall. (F-08) • Other units are trying to cover 360 degrees around the team. • If there are enough units to cover everything, increase the coverage of `interesting’ areas. • Interestingness of the area depends on proximity to walls and dangerous areas, tagged by the player. (F-09) Danger area

17. Shooting Formation • When enemy is spotted, everyone moves to face the enemy, or everyone goes into retreat. • Units move to avoid shooting one another. • Units seek positions with better coverage of the enemies.

18. Seeking a Safe Position • If player gives no orders, team moves to a safe position. • Seek proximity of cover. • Seek good coverage. (F-10)

19. Gregor Leban, Uroš Čibej, Martin Žnidaršič GUM FSM (F-11) init normal cover assault

20. Determining Orientation • Compute four viewing orientations for each unit. • Orientations depend on openness of terrain and tagged danger areas. • Pick the most important orientation that is not yet covered.

21. Assault • When enemy is spotted, everyone faces it and assaults. • Every unit picks the closest enemy and fires. • Move if a friendly unit close near the firing direction. • The player may adjust the formation during combat. • High mobility during an attack.

22. Technical Details • Development environment: Visual C++ • Libraries: • Simple DirectMedia Layer (SDL) • Video for Windows (VFW) • winsock • 450 KB of code • over 17000 lines in 110 files

23. Conclusions • High computational load. • Many parameters. • Weight tuning is complex. • Machine learning hard to use. • Commercial games use simpler logic.