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Panda3D Manual: Pursue

'Pursue' is a behavior where an AICharacter moves in the direction of a target NodePath until it reaches that entity, performing a change in direction of motion according to the entity's motion.

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In PandAI, 'Pursue' is defined as :

aiBehaviors.pursue(NodePath target, float priority)

priority is by default set to 1.0 and is used when using two or more steering behaviors on an AICharacter.


The velocity at which the AICharacter pursues is determined when you first create your AICharacter object using the AICharacter constructor.

  • Note : Pursue's direction is recalculated every frame to handle any change in the target's position.

The actual code working 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(0,0,55,0,-90,0)
 
        self.loadModels()
        self.setAI()
        self.setMovement()
 
    def loadModels(self):
        # Seeker
        ralphStartPos = Vec3(-10, 0, 0)
        self.pursuer = Actor("models/ralph",
                                 {"run":"models/ralph-run"})
        self.pursuer.reparentTo(render)
        self.pursuer.setScale(0.5)
        self.pursuer.setPos(ralphStartPos)
        # Target
        self.target = loader.loadModel("models/arrow")
        self.target.setColor(1,0,0)
        self.target.setPos(5,0,0)
        self.target.setScale(1)
        self.target.reparentTo(render)
 
    def setAI(self):
        #Creating AI World
        self.AIworld = AIWorld(render)
 
        self.AIchar = AICharacter("pursuer",self.pursuer, 100, 0.05, 5)
        self.AIworld.addAiChar(self.AIchar)
        self.AIbehaviors = self.AIchar.getAiBehaviors()
 
        self.AIbehaviors.pursue(self.target)
        self.pursuer.loop("run")
 
        #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()
run()

To get the full working demo, please visit :

https://sites.google.com/site/etcpandai/documentation/steering-behaviors/pursue/PandAIPursueExample.zip?attredirects=0&d=1