The Material Static operator lets you give particles material IDs that remain constant throughout the event. It also lets you assign a material to each particle based on its material ID. The operator can assign the same material ID to all particles, or different IDs to successive particles on a cyclical or random basis. The most common usage of this latter capability is with a Multi/Sub-Object material, for applying a different material to each particle.
The user interface appears in the parameters panel, on the right side of the Particle View dialog.
The Material Static operator gives you a choice of three different methods for assigning Material IDs to particles:
The highest ID number assigned to particles using the Cycle or Random option.
In general, set this to the same number of sub-materials in the Multi/Sub-Object material. If you set it to a smaller number, the operator will use only that many sub-materials, starting with the first and counting upward.
These settings let you choose the basis on which the operator changes material ID assignments, and specify the rate of change.
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 Particle Flow 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.
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, Particle Flow then moves through the sub-material list more rapidly than one (or more) particle per ID. That is, Particle Flow 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.
When on, and the last ID has been assigned, Particle Flow loops back around to the first ID and continues the cycle. When off, Particle Flow 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.