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Hierarchical Path Finding • Break the terrain for path finding to several ones hierarchically • Room-to to-room • 3D layered terrain • Terrain LOD • Pros • Speedup the search • Solve the problem of layered path finding Path Finding Challenges • Moving goal • Do you need to find path each frame • Moving obstacles • Prediction Scheme • Complexity of the terrain • Hierarchical path finding • “Good” path 31 32 Introduction to FSM (1/2) • Finite State Machine (FSM) is the most commonly used game AI technology today. • Simple • Efficient • Easily extensible • Powerful enough to handle a wide variety of situations • Theory (simplified) • A set of states, S • An input vocabulary, I • Transition function, T(s, i) • Map a state and an input to another state Introduction FSM (2/2) • Practical use • State • Behavior • Transition • Across states • Conditions • It’s s all about driving behavior • Flow-chart diagram • UML State chart • Arrow • Transition • Rectangle • State 33 34 An Example of FSM As a Diagram Gather Treasure Monster in sight No monster Flee FSM for Games • Character AI • “Decision-Action” model • Behavior • Mental state • Transition • Players’ action • The other characters’ actions • Some features in the game world Monster dead Fight Cornered 35 36 6
Implement FSM • Code-based FSM • Simple Code One Up • Straightforward • Most common • Macro-assisted assisted FSM Language • Data-Driven Driven FSM • FSM Script Language Coding an FSM – Code Example 1 void RunLogic(int *state) { switch(*state) { case 0: // Wander Wander(); if (SeeEnemy( SeeEnemy()) *state = 1; if (Dead()) *state = 2; break; case 1: // Attack Attack(); *state = 0; if (Dead()) *state = 2; break; case 2: // Dead SlowlyRot(); break; } } 37 38 Coding an FSM – Code Example 2 void RunLogic(FSM *fsm) { // Do action based on the state and determine next input input = 0; switch(fsm->GetStateID GetStateID()) { case 0: // Wander Wander(); if (SeeEnemy( SeeEnemy()) input = SEE_ENEMY; if (Dead()) input = DEAD; break; case 1: // Attack Attack(); input = WANDER; if (Dead()) input = DEAD; break; case 2: // Dead SlowlyRot(); break; } // DO state transition based on computed input fsm->StateTransition(input StateTransition(input); } 39 FSM Language Use Macros • Coding a state machine directly causes lack of structure • Going complex when FSM at their largest • Use macros • Beneficial properties • Structure • Readability • Debugging • Simplicity 40 FSM Language Use Macros – An Example #define BeginStateMachine … #define State(a) … … bool MyStateMachine::States(StateMachineEvent event, int state) { BeginStateMachine State(0) OnUpdate Wander(); if (SeeEnemy( SeeEnemy()) SetState(1); if (Dead()) SetState(2); State(1) OnUpdate Attack(); SetState(0); if (Dead()) SetState(2); State(2); OnUpdate RotSlowly(); EndStateMachine Data-Driven Driven FSM • Scripting language • Text-based script file • Transformed into • C++ • Integrated into source code • Bytecode • Interpreted by the game • Authoring • Compiler • AI editing tool • Game • FSM script engine • FSM interface } 42 41 7
Page 1 and 2: Contents • Search • Path findin
Page 3 and 4: Heuristic Search (2/2) • When we
Page 5: A* Algorithm (4/4) • State • Lo
Page 9 and 10: Event-driven Processing Model • D
Page 11 and 12: Locomotion • Character physically
Page 13 and 14: Steering Behaviors for Groups of Ch

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