Force Over Lifetime module
Particles can be accelerated by forces (such as wind or attraction) that are specified in this module.
Using the Force over Lifetime module
This module is part of the Particle SystemA component that simulates fluid entities such as liquids, clouds and flames by generating and animating large numbers of small 2D images in the scene. More info
See in Glossary component. When you create a new Particle System GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary, or add a Particle System component to an exiting GameObject, Unity adds the Force over Lifetime module to the Particle System. By default, Unity disables this module. To create a new Particle System and enable this module:
- Click GameObject > Effects > Particle System.
- In the InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
See in Glossary, find the Particle System component. - In the Particle System component, find the Force over Lifetime module fold-out.
- To the left of the fold-out header, enable the checkbox.
API
Since this module is part of the Particle System component, you access it through the ParticleSystem class. For information on how to access it and change values at runtime, see the Force over Lifetime module API documentation.
Properties
For some properties in this section, you can use different modes to set their value. For information on the modes you can use, see Varying properties over time.
| Property | Function |
|---|---|
| X, Y, Z | Force applied to each particle in the X, Y and Z axes. |
| Space | Selects whether the force is applied in local or world space. |
| Randomize | When using the Two Constants or Two Curves modes, this causes a new force direction to be chosen on each frame within the defined ranges. This causes more turbulent, erratic movement. |
Details
Fluids are often affected by forces as they move. For example, smoke will accelerate slightly as it rises from a fire, carried up by the hot air around it. Subtle effects can be achieved by using curves to control the force over the particles’ lifetimes. Using the previous example, smoke will initially accelerate upward but as the rising air gradually cools, the force will diminish. Thick smoke from a fire might initially accelerate, then slow down as it spreads and perhaps even start to fall to earth if it persists for a long time.