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.. _obstacle-avoidance:

Obstacle Avoidance
==================

'Obstacle Avoidance' is a behavior where an AI Character steers away from
obstacles in its path.

{{#ev:youtube\|xZnuWRiKL6I}}

--------------

In PandAI, obstacle avoidance is defined as :


.. code-block:: python
    
    aiBehaviors.obstacleAvoidance(float feeler_length)

Feeler length is the
range at which the obstacle can be detected by the AI Character

(Note : This does not correspond to actual length in render. The algorithm
computes the feeler’s length based on AI Character’s speed and size and also
the Obstacle size and the feeler length which is input to it simply a
multiplier)

--------------

For the algorithm to work, the obstacles need to be added to the world like
this : 

.. code-block:: python
    
    aiWorld.addObstacle(NodePath  obstacle)

Also you can
remove an obstacle at any time needed by using


.. code-block:: python
    
    aiWorld.removeObstacle(NodePath obstacle)



--------------

The full working code in Panda3D is :


.. 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.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)
            # Obstacle 1
            self.obstacle1 = loader.loadModel("models/arrow")
            self.obstacle1.setColor(0,0,1)
            self.obstacle1.setPos(2,0,0)
            self.obstacle1.setScale(1)
            self.obstacle1.reparentTo(render)
            # Obstacle 2
            self.obstacle2 = loader.loadModel("models/arrow")
            self.obstacle2.setColor(0,0,1)
            self.obstacle2.setPos(5,5,0)
            self.obstacle2.setScale(1)
            self.obstacle2.reparentTo(render)        
            
            self.pursuer.loop("run")
          
        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)
            
            # Obstacle avoidance
            self.AIbehaviors.obstacleAvoidance(1.0)
            self.AIworld.addObstacle(self.obstacle1)
            self.AIworld.addObstacle(self.obstacle2)
    
            #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/obstacle-avoidance/PandAIObstacleAvoidanceExample.zip?attredirects=0&d;=1