Flock
What is flocking? Flocking is an emergent behavior and is the resultant of the following forces:
cohesion – finds average position of neighbors and tries to move to that position separation – object keeps a certain distance between itself and its neighbor alignment – finds average direction in which all neighbors are moving and tries to move in that direction
Each NPC has a “visibility cone” and this is used to compute it’s neighbors. The neighbors contribute towards the forces mentioned above.
Tuners:
The angle and length of each NPC’s “visibility cone”.
Weight of cohesion, separation, and alignment (how much each sub-behavior of flock affects the overall flocking behavior).
Note
Flocking behavior is NOT a standalone behavior. It needs to be combined with other steering behaviors such as seek, pursue, flee, evade etc. to function.
https://www.youtube.com/watch?v=dkfnlqH06IY
Using PandAI’s flocking system:
// To create the flock flockObject = Flock(unsigned int flock_id, double vcone_angle, double vcone_radius, unsigned int cohesion_wt, unsigned int separation_wt, unsigned int alignment_wt) “flock_id” is a value identifying the flock.
“vcone_angle” is the visibility angle of the character (represented by a cone around it)
“vcone_radius” is the length of the visibility cone.
“cohesion_wt”, “separation_wt” and “alignment_wt” is the amount of separation force that contributes to the overall flocking behavior.
Some standard values to start you off with:
Type vcone_angle vcone_radius separation_wt cohesion_wt alignment_wt
Normal Pack 270 10 2 4 1
Loose Pack 180 10 2 4 5
Tight Pack 45 5 2 4 5
You could try experimenting with your own values to customize your flock.
To add your AI Character to the above created flock
flockObject.addAiChar(aiChar) # aiChar is an AICharacter object. After all the AI Characters are added to the flock, add the flock to the world.
aiWorld.addFlock(flockObject) # aiWorld is an AIWorld object. Specify the flock behavior priority. As mentioned earlier, flock behavior works with other steering behaviors.
# aiBehaviors is an AIBehaviors object. aiBehaviors.flock(float priority) # Turns the flock behavior off. aiWorld.flockOff(unsigned int flock_id) # Turns the flock behavior on. aiWorld.flockOn(unsigned int flock_id) # Removes the flock behavior. # Note: This does NOT remove the AI characters of the flock. aiWorld.removeFlock(unsigned int flock_id) # Returns a handle to the flock object. aiWorld.getFlock(unsigned int flock_id) The full working code in Panda3D :
import direct.directbase.DirectStart from panda3d.core import * from direct.showbase.DirectObject import DirectObject from direct.task import Task from direct.actor.Actor import Actor #for Pandai from panda3d.ai import * #for Onscreen GUI from direct.gui.OnscreenText import OnscreenText # Globals speed = 0.75 # Function to put instructions on the screen. font = loader.loadFont("cmss12") def addInstructions(pos, msg): return OnscreenText(text=msg, style=1, fg=(1, 1, 1, 1), font=font, pos=(-1.3, pos), align=TextNode.ALeft, scale=.05) class World(DirectObject): def __init__(self): base.disableMouse() base.cam.setPosHpr(0, 0, 85, 0, -90, 0) self.loadModels() self.setAI() self.setMovement() def loadModels(self): # Seeker self.flockers = [] for i in range(10): ralphStartPos = Vec3(-10+i, 0, 0) self.flockers.append(Actor("models/ralph", {"run": "models/ralph-run"})) self.flockers[i].reparentTo(render) self.flockers[i].setScale(0.5) self.flockers[i].setPos(ralphStartPos) self.flockers[i].loop("run") # Target self.target = loader.loadModel("models/arrow") self.target.setColor(1,0,0) self.target.setPos(0,20,0) self.target.setScale(1) self.target.reparentTo(render) def setAI(self): #Creating AI World self.AIworld = AIWorld(render) #Flock functions self.MyFlock = Flock(1, 270, 10, 2, 4, 0.2) self.AIworld.addFlock(self.MyFlock) self.AIworld.flockOn(1) self.AIchar = [] self.AIbehaviors = [] for i in range(10): char = AICharacter("flockers" + str(i), self.flockers[i], 100, 0.05, 5) self.AIchar.append(char) self.AIworld.addAiChar(char) self.AIbehaviors.append(char.getAiBehaviors()) self.MyFlock.addAiChar(char) self.AIbehaviors[i].flock(0.5) self.AIbehaviors[i].pursue(self.target, 0.5) #AI World update taskMgr.add(self.AIUpdate, "AIUpdate") #to update the AIWorld def AIUpdate(self, task): self.AIworld.update() return Task.cont # All the movement functions for the Target def setMovement(self): self.keyMap = {"left": 0, "right": 0, "up": 0, "down": 0} self.accept("arrow_left", self.setKey, ["left", 1]) self.accept("arrow_right", self.setKey, ["right", 1]) self.accept("arrow_up", self.setKey, ["up", 1]) self.accept("arrow_down", self.setKey, ["down", 1]) self.accept("arrow_left-up", self.setKey, ["left", 0]) self.accept("arrow_right-up", self.setKey, ["right", 0]) self.accept("arrow_up-up", self.setKey, ["up", 0]) self.accept("arrow_down-up", self.setKey, ["down", 0]) #movement task taskMgr.add(self.Mover, "Mover") addInstructions(0.9, "Use the Arrow keys to move the Red Target") def setKey(self, key, value): self.keyMap[key] = value def Mover(self,task): startPos = self.target.getPos() if self.keyMap["left"] != 0: self.target.setPos(startPos + Point3(-speed, 0, 0)) if self.keyMap["right"] != 0: self.target.setPos(startPos + Point3(speed, 0, 0)) if self.keyMap["up"] != 0: self.target.setPos(startPos + Point3(0, speed, 0)) if self.keyMap["down"] != 0: self.target.setPos(startPos + Point3(0, -speed, 0)) return Task.cont w = World() base.run() To get the full working demo, please visit: