You can divide particles into groups. The Group POP lets you sort its input particles into groups based on an various criteria. The Proximity POP creates a group for each particle containing other particles that are nearby. Other operators may create groups as a side effect as they work. For example, the Kill POP lets you create a new group with the killed particles.
Groups are very useful because almost every node gives the option to apply the node’s effects only to one or more groups in the input stream, instead of every particle in the stream. So, you can identify groups of particles based on certain properties, and then only apply some nodes to those groups, and not other particles.
For example, if you only want a node to affect particle older than one second, you could create a Group POP, set the group name to
old_enough, and set the rule to
$AGE > 1. Then, downstream from the group node, you can set the Source group parameter of another node to
old_enough to have it only act on the particles in that group (that is, particles older than one second).
How to create particle groups
|Create a group based on an expression|
|Create a group from the particles inside a boundary shape|
|Create a group for each particle containing its closest neighbors|
|Divide particles into multiple groups|
|Group particles based on the node that created them|
|Group particles based on their instanced geometry|
How to combine and filter particle groups
The controls on the Group POP's Combine tab let you create a group that is a combination of existing groups.
Create a Group node and connect the particle stream to its input.
In the parameter editor, click the Combine tab.
Enter the name of the new group to create in the left-hand field on the first row.
Enter the name of the group from which to take particles in the right-hand field (or click the box beside the equal sign so the exclamation point is visible if you want to start with particles not in the right-hand group).
Once you set up the top row, additional rows become available to further combine and/or filter the contents of the new group.
For the additional rows, on the right-hand side, enter the name of another group of particles you want to combine with or filter from the new group.
Use the menu on the left side to choose how to combine/filter the groups.
Use the menu to choose how to combine this group with the new group.
Click the box beside the equal sign so the exclamation point is visible if you want to do the logical opposite of the operation in the menu.
Almost all particle operators include a Source group parameter that lets you limit the effect of a node to only the members of a given group in the input stream. So once you've grouped the particles, you can apply different nodes selectively to the particles in the groups.