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.. _path-follow:

Path Follow
===========

'Path Follow' is a behavior where an AICharacter moves from one path to the
other without stopping at any path. It can be used for a patrolling type of
behavior.

{{#ev:youtube\|hIDyzUJgu2w}}

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

In PandAI, path follow is defined as :


.. code-block:: python
    
    aiBehaviors.pathFollow(float priority)
    aiBehaviors.addToPath(Vec3 position)
    
    aiBehaviors.startFollow() // Required to start the follow

Position is a point in
3D space which falls on the path which the AI Character needs to traverse.

(Note: that you need to add multiple positions to create a path say for
example Vec3(-10,10,0) Vec3(0,0,0) Vec3(10,10,0) Vec3(-10,10,0) will generate
a rectangular path in the XY plane)

Note: the addToPath works backwards. So, your last call to addToPath will be
your first position your AICharacter will go to.

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

The full working code in Pand3D 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 *
    
    class World(DirectObject):
    
        def __init__(self):
            base.disableMouse()
            base.cam.setPosHpr(0,0,55,0,-90,0)
            
            self.loadModels()
            self.setAI()
           
        def loadModels(self):
            # Seeker
            ralphStartPos = Vec3(-10, 0, 0)
            self.seeker = Actor("models/ralph",
                                     {"run":"models/ralph-run"})
            self.seeker.reparentTo(render)
            self.seeker.setScale(0.5)
            self.seeker.setPos(ralphStartPos)
            # Target1
            self.target1 = loader.loadModel("models/arrow")
            self.target1.setColor(1,0,0)
            self.target1.setPos(10,-10,0)
            self.target1.setScale(1)
            self.target1.reparentTo(render)
            # Target2
            self.target2 = loader.loadModel("models/arrow")
            self.target2.setColor(0,1,0)
            self.target2.setPos(10,10,0)
            self.target2.setScale(1)
            self.target2.reparentTo(render)
            # Target3
            self.target3 = loader.loadModel("models/arrow")
            self.target3.setColor(0,0,1)
            self.target3.setPos(-10,10,0)
            self.target3.setScale(1)
            self.target3.reparentTo(render)
            # Target4
            self.target4 = loader.loadModel("models/arrow")
            self.target4.setColor(1,0,1)
            self.target4.setPos(-10,-10,0)
            self.target4.setScale(1)
            self.target4.reparentTo(render)
            
            self.seeker.loop("run")
          
        def setAI(self):
            #Creating AI World
            self.AIworld = AIWorld(render)
     
            self.AIchar = AICharacter("seeker",self.seeker, 60, 0.05, 5)
            self.AIworld.addAiChar(self.AIchar)
            self.AIbehaviors = self.AIchar.getAiBehaviors()
            
            #Path follow (note the order is reveresed)
            self.AIbehaviors.pathFollow()
            self.AIbehaviors.addToPath(self.target4.getPos())
            self.AIbehaviors.addToPath(self.target3.getPos())
            self.AIbehaviors.addToPath(self.target2.getPos())
            self.AIbehaviors.addToPath(self.target1.getPos())
    
            self.AIbehaviors.startFollow()
    
            #AI World update
            taskMgr.add(self.AIUpdate,"AIUpdate")
            
        #to update the AIWorld    
        def AIUpdate(self,task):
            self.AIworld.update()            
            return Task.cont
     
    w = World()
    run()

To get the full working
demo, please visit :

https://sites.google.com/site/etcpandai/documentation/steering-behaviors/path-follow/PandAIPathFollowTutorial.zip?attredirects=0&d;=1