Setting Up Particle Collisions
When you set obstacles for particle clouds, a collision event is created for each particle type associated with that cloud. You can then determine how each particle type associated with the particle emission reacts to the obstacle. For example, the particles bounce by default, but they can also have other behaviors.
Collisions are just one of many different types of particle events that you can set up for a particle type. For more information on particle events, see Creating a Particle Event.
In addition to refining the collision event, you can further define how each particle type of the cloud reacts to the obstacle (see below), and you can set the accuracy of the particles’ collisions with the obstacle (see Setting the Accuracy of the Collision).
To create a collision with particles
1. Do either of the following:
- To set up an obstacle for a particle cloud, select the particle cloud and choose Modify > Environment > Set Obstacle.
or
- To set up an obstacle for a specific particle type, select the particle type in the explorer and choose Modify > Environment > Set Obstacle or create a Collision event as described in Upon Obstacle Collision.
2. Pick one or more objects in the scene that will act as obstacles for the emitted particles, hair, cloth object, or soft body object. Right-click to end the picking session.
3. The Obstacle property editor appears in which you can set the obstacle’s properties. See Setting Up Obstacles for more information.
Determining How Each Particle Type Reacts to the Obstacle
After you’ve created an obstacle for particles, you need to set up how each particle type defined for the cloud reacts to the obstacle.
1. Open the Particle Type property editor for each of the particle types that the obstacle affects (each particle type associated with the cloud).
2. Click the Envir. tab and modify the Obstacles properties on this page.
To set the elasticity and friction
• Set the values for Elasticity and Friction. The values set here are multiplied with the values that you have set for the Physical Parameters in the Obstacle property editor (see Setting the Collision’s Physical Behavior). The particle type values are a “scaling factor” for the obstacle’s values.
If you set the Collision action for the particle event to Bounce or Bounce & Emit (see Creating a Particle Event), the values set here have an impact.
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These parameters can be animated using standard animation controls (Birth/Abs/Age) and jittered with Variance values. For more information, see Animating Particle Type Parameters and Adding Variation to Particles. |
To keep this relationship simple, it’s usually best to set the values for the obstacle first, then tweak the parameters here. This way you can maintain the obstacle’s parameters as a constant.
• Elasticity controls the amount of influence that gravity has on the particles as they bounce off obstacles. A low value makes the particles fall quickly without much bounce while a high value makes the particles bounce more.
• Friction is the amount of influence that surface friction has on the particles as they collide with the obstacle. A high value makes them stick to the obstacle while a low value makes them slide off.
To consider the size of the particles for collisions
• Select Use Size for Collision to consider the size of the particle when it collides with the obstacle. This creates more of an offset between the particles and the obstacle, depending on the size of the particle.
Setting the Accuracy of the Collision
On the Collisions page in the ParticlesOp, FluidOp, and ExplosionOp property editors, you can set the number of Iterations and Interframes, which specify the number of times that the particle’s position is calculated per interval or per frame, respectively.
Depending on the collision, you can set the values higher for situations in which particles collide with multiple obstacles in the same step and there is undesirable behavior. Basically, the higher the parameter values here, the more accurate the results, but the longer the calculation times.
If you’re using the Explosion simulator, you can also select Check Particles, which detects collisions between particles and obstacles and calculates how the particles will respond. If this option is off, only collisions with structures are detected.
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