In a State compound, a trigger is something that causes an effect to happen when its value is reached, such as when the particle reaches a certain size (trigger), it disappears (effect), like blowing bubble gum and having it pop when it gets too big.
When this compound’s value is reached, the effect that is defined with another compound is executed. This effect compound can be plugged into the same State compound or it can be plugged into another State compound to which you transition when the trigger value is reached.
Particle effects can be triggered using many different criteria, such as a particle’s age, every nth particle or frame, a particle’s position (in XYZ), a particle’s speed, a particle’s collision with an obstacle, and so on.
Most of the compounds that can be used as triggers are found in the Conditionals group on the Particles tab. However, you can also use any other node or compound that you create, as long as it can be plugged into a State compound’s Trigger port (it needs to be a Boolean value).
To set a trigger
1. Create a particle emission—see Creating ICE Particle Emissions for information.
2. Set up a base state system as described in Creating a State System.
3. In the ICE tree’s preset manager, click the Task tab and select Particles.
4. Drag a compound you want to use as a trigger and plug its Result output into the Trigger port of a State compound.
Most compounds that can be used as triggers are found in the Conditionals group on the Particles tab. See Types of Triggers for a list of possibilities.
5. In the trigger compound’s property editor, set the value that you want to use as the trigger.
For example, if you’re using the Test Particle Reached Age Limit as the trigger compound, you need to have a Set Particle Age Limit compound plugged into the Emit compound. Then in the Set Particle Age Limit property editor, you must specify the age limit, which is the trigger value. If you define 3 as the particle’s age limit, the effect compound that you have defined is executed when the particle reaches the age of 3.
6. If you want to change states upon reaching the trigger value, select the state ID of the state to which the particles will transition by selecting it from the Change State on Trigger list. See Setting the Particle’s State ID for information.
You can define a new behavior/effect in this new state. The particle stays in this new state until it is forced to change to another state using the Change State on Trigger option in that State compound.
7. Set up the effect you want to happen when the trigger value is reached, as described in Defining the Effect.
You can select a trigger compound from the Conditionals group on the Particles tab. You can also use any other trigger node or compound as long as it can be plugged into a State compound’s Trigger port (it needs to be a Boolean value).
This is the basic list of trigger compounds in the Conditionals group:
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Every Nth Frame |
Uses specific intervals of frames as a trigger for an effect. For example, you could spawn particles at every 30th frame. |
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Every Nth Particle |
Uses specific particle intervals as a trigger for an effect. For example, you could set a new size for every 10th particle that is born. |
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Test Bounding Box |
Uses a minimum/maximum number of particles in X/Y/Z direction within the particle’s bounding box as a trigger for an effect. |
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Test Collision with Surface |
Uses the particle’s collision with an obstacle as a trigger for an effect. See About ICE Particle Collisions for more information. |
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Test Current Frame |
Use a specific frame in the timeline as a trigger for an effect. |
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Test Current Time |
Use a specific time (in seconds) in the timeline as a trigger for an effect. |
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Test Distance to Goal |
Uses the distance to an object defined as a goal for particles as a trigger for an effect. See ICE Particle Goals for more information. |
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Test Distance to Neighbors |
Uses the distance from one particle to its neighboring particle as a trigger for an effect. |
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Test Distance to Surface |
Uses the distance to an object as a trigger for an effect. You can set a cutoff distance too. |
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Test Inside Geometry |
When particles are inside a geometry volume, it triggers the effect. You must plug in an object’s Get Data node into the compound’s geometry port. |
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Test Inside Null |
When the particles are within the shape of a null, it triggers the effect. The null must be a 3D geometry shape for this to work — change the Primary Display Icon of the null in its property editor. |
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Test Is Spawned Particle |
Uses the fact that the particles are spawned as a trigger for an effect. See Spawning ICE Particles for more information. |
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Test Num Particles |
Uses a certain number of particles emitted in a point cloud as a trigger for an effect. |
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Test Particle Age |
Uses the particle’s age value as a trigger for an effect. For example, if you specify 3 as the Value, the effect is triggered when the particle has lived for 3 seconds. This value cannot exceed what is set for the particle in its Set Particle Age Limit compound. See ICE Particle Lifespan for information. |
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Test Particle Position |
Uses the particle’s position in global XYZ as a trigger for an effect. For example, you could have a particle disappear when it reaches a certain global Y position. |
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Test Particle Reached Age Limit |
Uses the particle’s age limit value as a trigger for an effect. Make sure that you have the Set Particle Age Limit compound plugged into the Emit compound so that the state knows what the particle’s age limit is. See ICE Particle Lifespan for information. |
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Test Particle Size |
Uses the particle’s Size value as a trigger for an effect. See ICE Particle Size for information. |
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Test Particle Velocity |
Uses the particle’s velocity as a trigger for an effect. For example, you could have a particle change color when it reaches a certain velocity value. See ICE Particle Speed for information. |
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Test Random Probability |
Uses a probability factor with a time variance as a trigger for an effect. |
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Test Should Drip |
Uses certain conditions that determine when a sliding particle should drip off an object as a trigger for an effect. See ICE Particles Sliding on Obstacles for more information. |
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Test Should Unstick |
Uses certain conditions that determine when a stuck particle should unstick from (fall off) an object as a trigger for an effect. See ICE Particles Sticking to Obstacles for more information. |
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Test Time in State |
Uses the amount of time in seconds that the particle has been in the current state as a trigger for an effect. This is used in conjunction with the Start Timer compound. See Setting Particle Timers for information. |
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Test Timer |
Uses a certain amount of time passing as a trigger for an effect. You use this in conjunction with the Start Timer compound. See Setting Particle Timers for information. |
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Test Visibility from Camera |
Uses the particle’s distance from the camera as a trigger for an effect. Only particles that are within visibility distance for the camera can trigger an effect. You must plug in a camera’s name output into this compound. |
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Test Weight Map Value |
Uses the values on an object's weight map as a trigger for an effect. |
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