<     > 

Defining the Effect

After you have selected a trigger for a state, you must define the type of effect that you want to occur. An effect is something that happens (the particles behavior changes) when a trigger’s value is reached.

An effect compound can be plugged into an Execute on Trigger port of the same State compound as the trigger compound, or it can be plugged into another State compound to which you transition when the trigger value is reached. Sometimes you may want to switch to another state because you want to develop a larger or more modular effect, and having several State compounds makes working with the compounds more flexible and easier to manage.

There are many different types of effects that you can create, from the classic bouncing particles off an obstacle to a simple change of particle color. Basically, any compound that can cause a change in particle behavior or properties can be used as an effect compound. See Types of Effects for more ideas.

An effect compound can be evaluated either once at the start of the state simulation, or it can be evaluated at every frame of the simulation, which is what you want for most effects.

To set up an effect

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. Select a trigger compound as described in Selecting the Trigger.

4. In the ICE tree’s preset manager, click the Task tab and select Particles.

From the groups on the Particles tab, drag a compound you want to use as an effect. The compounds that can be used as effects are found in many different groups on the Particles tab. See Types of Effects for a list of possibilities.

5. Plug the effect compound into the same State compound in which the Trigger compound is plugged, or in a new State compound to which you transition when the trigger value is reached.

Do either of the following:

• Plug the effect compound’s Execute output into an Execute on Trigger port on the same State compound in which the Trigger compound is plugged. This port executes whatever compound is plugged into it only once when the trigger value is reached. The particles do not remain in this state.

You can define more than one effect to be executed at the same time: just plug its Execute output into another Execute port in the State compound.

or

• If you’re defining the effect in another state to which you’re transitioning, plug it into either of these ports in the target State compound:

- Execute Once on Enter State: executes the effect compound plugged in here at the first frame that the state is entered. This is useful for compounds such as Delete Particles or Unstick from Surface, where you want the action to be performed only once, not at every frame.

- Execute Every Frame: executes the effect compound plugged in here at every frame so that the particles continue to be evaluated throughout the simulation.

6. In the effect compound’s property editor, set the parameters to define the behavior of the particles. For example, if you’re using a gravity force as an effect, you need to define its strength.

Types of Effects

The effect compounds are found in the Motion Control, Surface Interaction, Goals, Spawning, Strands, or Deleting Particles groups on the Particles tab. However, you can use any compound that can cause a change to particles, such as compounds in the Forces or Setters groups. For example, an effect could be gravity (a force) pulling the particles down or having particles change their velocity (set particle velocity).

Here are some of the compounds most frequently used for state effects:

Autodesk Softimage v.7.5     <     >