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.. _evade:

Evade
=====

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

{{#ev:youtube\|JchuRRHqPUQ}}

In PandAI, 'Evade' is defined as :



.. code-block:: python
    
    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 :



.. code-block:: python
    
    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