1. CIS 487/587 Bruce R. Maxim UM-Dearborn
Group Behavior
CIS 487/587
Bruce R. Maxim
UM-Dearborn
12/4/2018

2. Flocking
Emergent behavior that appears complex and purposeful, but is really derived from simple rules followed blindly by the agents
Composed out of three group behaviors
Cohesion (steering toward neighbors’ center of mass)
Separation (creates force that steers away from neighbors)
Alignment (keeps agent heading in the same direction as neighbors)
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3. Combining Steering Behavior
In an FPS you might want a bot that combines path following, separation, and wall avoidance
In an RTS you might want a group of bots to flock together while wandering, avoiding obstacles, and evading enemies
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4. Slides based on the Code from Advanced 3D Game Programming by Kenneth Finney
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5. Group Behavior Rules
Members of a group should not bump into one another (collision avoidance)
Each group member should try to maintain its position relative to the center of the group (swarm centering)
Each member of the group should attempt to match its velocity with the average velocity of the other members (velocity matching)
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6. AIDropPoints
Execute the fps.starter demo and open the World Creator Interface
On lower right side, drill down and click on MissionObjects/System/SimGroup
Call the object AIDropPoints and switch to the World Editor Inspector (F3)
Make AIDropPoints an instant group using the Alt key and left mouse button
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7. Swarm Switch to the World Creator (F4)
On lower right side, drill down and click on MissionObjects/System/SimGroup
Call the object Swarm and switch to the World Editor Inspector (F3)
Make Swarm an instant group using the Alt key and left mouse button
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8. SpawnSphere - 1
Exit the Mission Editor (F11) and enter camera fly mode (F8)
Find a good location for an swarm and place it 20 feet off the terrain
Switch back to the Mission Editor (F11) and enter World Creator (F4)
Drill down to Shapes/Misc on lower right and click on SpawnSphereMarker
Place at least two more in the world
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9. SpawnSphere - 2 Switch to World Editor Inspector (F3)
Select all 3 SpawnSpheres in upper left (Ctrl and left mouse click)
Click on expand all
Changes the radius field to 10 and press Apply button
Save the mission and exit to the desktop
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10. Code Modifications
Add this line to the server\script\game.cs function onServerCreated and disable the aiGuard code
exec(“./swarm.cs”);
// exec(“./aiGuard.cs”);
At the end of the same game.cs file add this line to start the bot placement process
Schedule(3000, 0, “CreateBots”);
Save game.cs and copy the file swarm.cs to the server\script folder
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11. Test Swarm Run the test application again. Open the console and type
InitSwarm( );
To add some more bots to the swarm type
SpawnASwarm( );
Close the console window and watch them go
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12. Chasing Swarm
Replace the SwarmBotDB::DoScan function in the file swarm.cs
Add the code for functions AIPlayer::FindLeader AIPLayer::GetClosestHuman
Save the file and get ready to test the new behavior
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13. Test Chasing Swarm Run the test application again.
Open the console and type
InitSwarm( );
To add some more bots to the swarm type
SpawnASwarm( );
Close the console window and watch them go
See how close (or far away) to get swarm to chase the player avatar
12/4/2018