TYPE: POP
TITLE: Stream POP

The Stream POP is used to birth particles where streams of other
particles intersect. Birthing is done when the density of colliding 
particles is greater than or equal to some specified threshold.
Spatial partitions are created and the threshold specifies how many 
particles need to be present in one of these partitions before
birthing occurs. Local variables are usable in parameters denoted with a *.

Parameters: 
    Activation                  - Turns the POP on and off	/activate
Source
    Birth Position              - Where in the partition new particles are
                                  to be birthed
				/birthpositionx /birthpositiony /birthpositionz
    Division Size               - Size of each uniform partition	/sizex /sizey /sizez
    Offset of Grid              - Subtracted from each uniform partition
                                  to move away from its default anchor	
						/offsetx /offsety /offsetz
    Enable Stream <n>           - Stream <n> will be used
    Group <n>                   - Group to use for stream <n>
    Threshold <n>               - Number of stream <n> particles required
                                  in partition to birth		/threshold<n>
    Kill original particle <n>  - Kills original particle in that stream
Birth
    *Birth Probability          - How many particles to birth in each
                                  partition		/probmin /probmax
    Birth Group                 - Group to contain birthed points
    Preserve Group              - Add particles to group instead of clearing group first
    *Life Expectancy            - How long the particle will live in seconds	/life
    *Life Variance              - Variance of life expectancy in seconds	/lifevar
Attributes
    Initial Velocity            - How to set initial velocity
                                  (inherited velocity = avg. velocity of
                                  particles in partition)
    *Inherit Velocity           - How much of inherited velocity to use	/inherit
    *Velocity                   - Used to set or add to velocity	/velx /vely /velz
    *Variance                   - Variance of set or added velocity	/varx /vary /varz
    Ellipsoid Distribution      - Distribute the velocities in a spheroid
                                  of size determined by Variance, rather than
                                  a cube.
    *Origin Index               - Index as used in origin	/originindex

Local Variables
    DENSITY               - total number of particles from enabled streams
                            contained in the partition.
    THRESH                - sum of all enabled stream thresholds
    TIMEINC               - frame time increment
    TX TY TZ              - birth position

See Also: Location, Source, Split
