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Basic Steering of Game Agents

Featuring Guest professorsStephen Sheneman

&Michael Wilkens

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Topics Covered

• Kinematics• Facing and Alignment• Seek and Flee• Arrive• Pursuit• Evade• Wander• Path following

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Kinematics

• Velocity• Vectors• Max speeds• Acceleration• Game world

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Facing

• Help create illusion of intelligence• The character looks at its target• Changes its orientation so that it is facing its

target• http://www.youtube.com/watch?

v=i1SFm62Etyc

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Align

• The character changes its orientation to that of its target

• Have to do special calculations because orientation wraps back around to 0

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Seek

• Vectors• Target character• Velocity• Max speeds• Kinematics controlling to look like normal

behavior vector handling and velocity handling basics

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Flee

• Opposite of seek• Desired velocity

aims for opposite vector

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Arrive

• Using seek but with code changes to slow down once target gap is closing

• Opposite of arrive is leave but really it is just flee. Velocity remains the same

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Pursue

• Similar to Seek• Uses predictions• Pursue that degree!

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Evade

• Handle prediction but moving away• Evade is an amped up Flee

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Wander

• Move from random target to random target• Focus on jitter• Facing in the right direction• Turn speed

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Wandering

• The character moves forward, but changes direction so it appears to meander

• Alternatively, have a target on a circle, change the position of it randomly, and have the character seek that

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Path Following

• Take a predefined path, and set its predicted points and have the character seek to those points as it goes along– Advantage– Disadvantage: character may take undesired short

cuts

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Path following

• Patrolling “look out! here comes the pat!”• Line segments vs. splines• Coherence geometric algorithms• Performance of steering is generally O(1) with

path following getting into O(n)• http://www.youtube.com/watch?v=BTZqaAG-

Xjo

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Thanks for watching!

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