Action Time Frames

Most actions in Particle Flow operate on particles in either of two time frames: once, when the particle first enters the event, or on a continuous basis, potentially changing particle behavior at each integration step (that is, the whole time the particle is in the action’s event). Some actions can work only in one time frame, while others can work on an instantaneous or continuous basis, depending on their settings. The tables in this topic list each action with its time frame.


Operator Time Frame
Birth n/a
Birth Paint Once, except continuous when Lock At Painted Objects Position or Rotation is on
Birth Script n/a
Birth Texture Once
Delete n/a
Force Continuous
Group Once
Group Selection Depends on Selection Update setting
Initial State Once, except continuous when Lock To Icon TM Position or Speed is on
Keep Apart Continuous
Mapping Continuous
Mapping Object Depends on Type setting
Material Dynamic Continuous
Material Frequency Once
Material Static Once
Placement Paint Depends on Data Update setting
Position Icon Once, except continuous with Lock On Emitter
Position Object Once, except continuous with Lock On Emitter
Preset Flow n/a
Rotation Once, except continuous with Speed Space Follow
Scale Once, except continuous with Absolute and Relative options
Script Operator Depends on script
Shape Once, except continuous when Scale % or Variation % parameters are animated
Shape Facing Continuous
Shape Instance Once, except continuous with Animated Shape
Shape Mark Once, except continuous with Align To Surface Animation
Speed Once
Speed By Icon Continuous
Speed By Surface Depends on setting
Spin Once, except continuous with Speed Space Follow
Split Group Continuous
n/a=not applicable  


Most tests in Particle Flow function only as tests. At each integration step, they check each particle for the specified conditions, and then return the test result: True or False. So, as tests, they work on a continuous basis. For example, Age Test checks each particle's age at every integration step, because particles might not reach the specified age until remaining in the event for a while, and also because another action in the event might change or reset particle age.

The principal exceptions to this are the Split tests, which test each particle only when it first enters the event. That is, a Split test splits the particle stream only once for each particle that enters the event. Any particles that remain in the event are not subject again to being split off from the stream by the same test. Also, the Send Out test performs no test, but simply moves particles along to the next event.

Some tests also function as operators, in that they directly affect particle behavior. These are the ones listed here, and the specified time frame is related to the operator functionality, not the test.

Test Time Frame
Collision Spawn Continuous
Find Target Continuous
Go To Rotation Continuous
Script Test Depends on script
Spawn Continuous, except once with Once