• derived nodes inherit all messages from their base classes
  
• see reset method for default settings
  
• this node can cause unpredictable behavior if the nodes being moved to the floor are also set as floor
  
• the object can be oriented to the slope of the floor by setting the upright mode to false
  

constructor gravity

method reset

1 set height to zero
2 set speed to 1.0 feet/second
3 set upright to true

method message

1 set the angle of the object to the surface or upright
2 toggle the upright mode
3 set the fly mode to enable or disable gravity
4 toggle the fly mode
5 set the speed in feet/second
6 set the height above the surface

method app

1 if not in fly mode then check for ground

method checkGround

1 set up intersection segment
2 get self matix
3 get parent matrix
4 if an intersection with an object is found

4.1 Get the intersection transformation matrix.
4.2 if not upright then adjust the angle to the surface normal
4.3 Set the new transformation and return.