Speed Test
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Particle View Click Speed Test in an event or add Speed Test to the particle system and then select it.

Speed Test lets the particle system check particle speed, acceleration, or the rate of circular travel, and branch accordingly. The test provides a number of variants that let you test speed or acceleration on specific axes, or simply whether the particle is accelerating or decelerating.


The user interface appears in the parameters panel, on the right side of the Particle View dialog.

The first interface element is a drop-down list that lets you choose the type of measurement to test:

Test True if Particle Value

Lets you specify whether the test passes particles on to the next event if the speed test succeeds or fails. Available for all tests except True When Accelerates/Decelerates. Default=Is Greater Than Test Value.

By default, Speed Test returns True if the value tested for exceeds the Test Value quantity, but you can choose Is Less Than Test Value as well. For example, if you use the Velocity Magnitude test type and set Test Value=200 and Variation=0, and choose Is Less Than Test Value, then particles will move to the next event only when they travel faster than 200 units per second. Any particles traveling 200 units per second or slower stay in the current event unless they later exceed that speed or another test returns True.

Test Value

The specific speed or acceleration to test for. The unit of measurement depends on the type of test; see above. Default=300.0.


The amount by which value tested for can vary randomly. Default=0.0.

To obtain the actual test value for each particle, the system multiplies the Variation value by a random number between -1.0 and 1.0, and then adds the result to the Test Value setting. For example, if Test Value=300 and Variation=10, then tested value for each particle would be between 290 and 310.

Sync By

Choose the time frame to use when animating Test Value and Variation. For further information, see Animation Offset Keying group.

  • Absolute TimeAny keys set for parameters are applied at the actual frames for which they're set.
  • Particle AgeAny keys set for parameters are applied at the corresponding frames of each particle's existence.
  • Event DurationAny keys set for parameters are applied to each particle starting when it first enters the event.

Uniqueness group

The Uniqueness setting enables randomization of the test value variation.


Specifies a randomization value.


Calculates a new seed using a randomization formula.