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.. _projectile-intervals:

Projectile Intervals
====================

Projectile intervals are used to move a NodePath through the trajectory of a
projectile under the influence of gravity.



.. code-block:: python
    
    myInterval = ProjectileInterval(<Node Path>,
      startPos = Point3(X,Y,Z), endPos = Point3(X,Y,Z),
      duration = <Time in seconds>, startVel = Point3(X,Y,Z),
      endZ = Point3(X,Y,Z), gravityMult = <multiplier>, name = <Name>)



All parameters don't have to be specified. Here are a combination of
parameters that will allow you to create a projectile interval. (If startPos
is not provided, it will be obtained from the node's position at the time that
the interval is first started. Note that in this case you must provide a
duration.)

-  startPos, endPos, duration - go from startPos to endPos in duration seconds
-  startPos, startVel, duration - given a starting velocity, go for a specific
   time period
-  startPos, startVel, endZ - given a starting velocity, go until you hit a
   given Z plane


In addition you may alter gravity by providing a multiplier in 'gravityMult'.
'2' will make gravity twice as strong, '.5' half as strong.'-1' will reverse
gravity.

Here's a little snippet of code that will demonstrate projectile intervals:



.. code-block:: python
    
    camera.setPos(0,-45,0)
    
    # load the ball model
    self.ball = loader.loadModel("smiley")
    self.ball.reparentTo(render)
    self.ball.setPos(-15,0,0)
    
    # setup the projectile interval
    self.trajectory = ProjectileInterval(self.ball,
                                         startPos = Point3(-15,0,0),
                                         endPos = Point3(15,0, 0), duration = 1)
    self.trajectory.loop()