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Panda3D Manual: Evade

'Evade' is an AI behavior where an AICharacter will move in the opposite direction to a target NodePath or position.

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In PandAI, 'Evade' is defined as :

aiBehaviors.evade(NodePath target, double panic_distance, double relax_distance, float priority)

where :

Panic Distance is the radius of detection.

Relax Distance is the distance from the panic distance radius after which the object should stop evading once evade has been initiated.

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 evades is determined when you first create your AICharacter object using the AICharacter constructor.

  • Note: 'Evade' recalculates the direction every frame and so is less efficient than Flee for a static object.

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(0,0,55,0,-90,0)
 
self.loadModels()
self.setAI()
self.setMovement()
 
def loadModels(self):
# Seeker
ralphStartPos = Vec3(-10, 0, 0)
self.evader = Actor("models/ralph",
{"run":"models/ralph-run"})
self.evader.reparentTo(render)
self.evader.setScale(0.5)
self.evader.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("evader",self.evader, 100, 0.05, 5)
self.AIworld.addAiChar(self.AIchar)
self.AIbehaviors = self.AIchar.getAiBehaviors()
 
self.AIbehaviors.evade(self.target, 5, 5)
self.evader.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/evade/PandAIEvadeExample.zip?attredirects=0&d=1