TYPE: POP
TITLE: Proximity POP

The Proximity POP can be used keep track of the other particles in 
the proximity of the given particles.

This POP modifies the following attributes: nearest, nearestdist
and numproximity.

Parameters:
    Activation             - Turns the POP on and off
    Source Group           - Subset of points to act on

    Add Nearest Neighbour Attribute   - id of nearest particle
    Add Nearest Distance Attribute    - distance to nearest particle
    Add Number in Proximity Attribute - number of particles within
                                        proximity radius.
    Create Proximity Particle Groups - create point groups of particles
                                       that fall within a given radius of
				       source particles
    Create Groups For      - particles to use to create proximity groups
    Group Name Root        - root name of groups to be created. The group
                             names will be made by appending the ID
                             or point number of the source particle.
    Include Self in Proximity Groups - specifies whether or not to include
                                       the source particle in the proximity
				       group.
    Proximity Radius       - radius within which other particles
                             are considered in proximity       /proximityradius
    Use Point Numbers Instead of IDs - point numbers are used to fill the
                                       nearest attribute and create the
				       proximity group names.

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