2009

Rate group
These settings let you choose the basis on which the operator changes material
ID assignments, and specify the rate of change.
Per Second Sets the number of times per second that the assigned material
ID is incremented. If this value is the same as the rate at which particles enter
the event, then one ID is assigned per particle. If it's lower, then multiple
particles are given the same ID, or if it's higher, then the software increments
the assigned ID faster than 1 per particle.
For instance, if particles enter the event at intervals of 1/60 of a second, and
Per Second=30, then each pair of particles will be assigned the same ID. Or if
particles enter the event at intervals of 1/15 of a second, and Per Second=30,
then the ID is incremented (or changed randomly) twice per particle.
Per Particle Sets the number of particles that must appear before material ID
assignment changes. For example, If you set Per Particle=3, the material ID
changes every three particles.
If you set Per Particle to a number less than 1.0, the software then moves
through the sub-material list more rapidly than one (or more) particle per ID.
That is, the software divides this value into 1.0, and adds the result to the
current material ID to obtain the next one. For example, with eight
sub-materials, if you set Per Particle=0.33, and use the Cycle option, the
following series of IDs will result: 1, 4, 7, 2, 5, 8, 3, 6, 1, ... In general, this
option is useful only with the Cycle option.
Loop When on, and the last ID has been assigned, the software loops back
around to the first ID and continues the cycle. When off, the software assigns
the last cycle ID to all subsequent particles. Available only with the Cycle
assignment method. Default=on.
For example, say you want the first eight particles that enter the event to use
different materials, and all subsequent particles to use a ninth material. To do
so, you would create a nine-sub-material Multi/Sub-Object material and assign
it to the Material Static operator. Turn on Assign Material ID, choose the Cycle
assignment method, and set # Sub-Materials=9. For Rate, use the default settings
of Per Particle and 1.0. Lastly, turn off Loop.
Uniqueness group
The Uniqueness setting varies the sequence of assigned IDs with the Random
option.
Seed Specifies a randomization value.
2922 | Chapter 14 Space Warps and Particle Systems