TYPE: POP
TITLE: Interact POP

The Interact POP is used to add inter-particle forces. This allows 
particles to be attracted and/or repulsed by other particles. To help 
visualize the effect of this operator, turn on the template flag to 
view the acceleration guides.

This POP modifies the following attributes: accel.

Parameters:
    Activation                   - Turns the POP on and off		/activate
    Source Group                 - Subset of points to act on
Influence
    Particle Radius              - The radius of the particle. The applied
                                   force will be constant in this region.
    Scale                        - Multiplier for computed radius	/pscale
    Radius                       - Radius to use for particle radius	/pradius
    Effect Radius                - The extent of the effect from the particle's
                                   surface. The applied force takes the shape
                                   of a half cosine in this region.
    Scale                        - Multiplier for computed radius	/escale
    Radius                       - Radius to use for the effect radius	/eradius
Behavior
    Overlap Behavior             - What happens when the centers of two 
                                   particles overlap
    Influence Type               - How the effect radius is used
	Particle Intersects Effect - Particle exerts force when another
                                    particle enters the shell of influence
	Effect Intersects Effect  - Particle exerts force when another
                                    particle's shell of influence enters its
                                    own shell of influence
    Charge Behavior              - Determines which charge will affect force
    Rolloff Exponent             - Exponent to apply to the roll-off function.
                                   Smaller values increase the effect at any
                                   given distance with the radius     /exponent
    Force Multiplier             - Multipliers for each component of the force
					/multiplierx /multipliery /multiplierz
Defaults
    Ignore Charge                - Ignore the particle charge
    Override Charge              - Override the particle charge
    Charge                       - Charge to use for override		/charge
    Ignore Mass                  - Ignore particle mass
    Override Mass                - Override particle mass
    Mass                         - Mass to use for override		/mass

Local Variables 
    Overview - The standard local variables are usable in this POP.  Please
               refer to the Houdini manual for more details.
