TYPE: POP
TITLE: Group POP

The Group POP generates groups of particles according to various criteria.
These groups can then be used to apply POPs selectively to specific
particles.

Note that to choose particles based on a particular criteria, the Enable 
toggle box for that option must be checked on.

Parameters:
    Activation       - Turns the POP on and off		/activate
Create
    Source Group     - Subset of points to act on
    Group Name       - Name of new group to contain chosen points
    Preserve Group   - Add particles to group instead of clearing group first
Create: Rule
    Overview         - Choose based on rule
    Predefined Rules - Use some predefined rules 
    Rule             - If this rule evaluates to 1, choose point
Create: Bound
    Overview         - Choose based on point being in bounding volume 
    Bounding Type    - Type of bounding volume to use
    Center           - Center of bounding volume	/tx /ty /tz
    Size             - Size of bounding volume		/sizex /sizey /sizez
    SOP              - Sop containing geometry to use as bounding volume
    Ignore Transform Object - Transform geometry to transform object space
    Density Minimum  - For metaball volume, will not choose this point
                       if the density is below minimum		/densitymin
Create: Gen
    Overview         - Choose based on generator
    Generators       - Particles created by these generators will be chosen
Create: Rand
    Overview         - Place particles randomly into n groups
    # of Groups      - Number of groups to create. The groups names will 
                       be based on the group parameter. 	/multi
    Group Index      - Override the group the particle will be placed
                       into.					/multiindex
Create: Inst
    Overview         - Choose based on the instance attribute
    Instances        - Instance values to put into group
Combine
    Overview         - Combines groups based on boolean operators and
                       combination methods.
    First field      - Group to operate on.
    Button           - Negates third field.
    Third field      - Name of combined group.
    Menu             - Operation to perform. etc.
Select
    Select group(s) in detail - Select the named groups in the detail
    Select Group              - groups to select

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