Force Fields

Force fields affect particles by attracting, repelling or accelerating them in some direction and can be used to model gravity, wind and other natural effects. You can add force fields using the object browser.

Note

Alternatively, directly place a force field in the scene by right-clicking on the scene view while holding Ctrl.

Types

Attraction field

Attraction fields are spherical force fields that pull particles towards their center. You can also make them repel particles by setting a negative Strength value.

Acceleration field

Acceleration field accelerate particles in specified direction. They also allow you to subdivide the force area with a grid, where each grid cell has a different force direction and strength, which is useful for organic looking particle motion.

Vector field

Vector field are loaded from file. Particles follow the vectors that are specified by the field.

Noise field

Noise fields generate a random turbulent force field. You can define the properties of the noise generation like the frequency and the number of noise octaves. This type of force field is perfect for creating organic and unpredictable patterns.

Drag field

Drag fields slow down particles mimicking the effects of drag. You can specify how much the particles’ velocity and size impact their behavior in the drag field.

Properties

The following properties can be adjusted in the property window to change the behavior of a force field.

General

Property	Description
Infinite	Whether the force field has an infinite area of effect.
Exclusion list	List of particle types not affected by the force field. Add and remove particle types via the context menu (right-click).

Physics

Property	Description
Strength	How strongly particles are affected by the force field. Negative values reverse the force direction. Attraction fields then repel particles, for example.
[Acceleration field] Strength variance	How much the force strength varies between cells of the grid.
[Acceleration field] Direction	Direction of the area force. For 3D effects, the direction is composed of roll, yaw and pitch.
[Acceleration field] Direction variance	How much the force direction varies between cells of the grid.
[Acceleration field] Grid	Number of cells used for the randomization grid. Each grid cell has a slightly different, randomly selected force direction and strength, which is influenced by the variance parameters for direction and strength. Click to randomize the strength and direction values of the grid cells.
[Vector field] Resource	File that supplies the vectors for the vector field.
[Vector field] Filter	How velocity values are interpolated between the cells of the vector field.
[Vector field] Tightness	How directly particles follow the vectors in the force field. If set to 0, the field applies forces to the particles over time. If set to 1, particles follow the vectors in the force field directly.
[Noise field] Octaves	How many layers of noise are blended together to produce the final velocity vector.
[Noise field] Frequency	Base frequency of the noise generation. Higher values produce more turbulent noise fields.
[Noise field] Persistence	How much the amplitude changes after each noise octave.
[Noise field] Lacunarity	How much the frequency changes after each noise octave
[Noise field] Animated	Whether the noise field is animated.
[Noise field] Time scale	How fast the noise field changes.
[Noise field] Time base	Time offset of the noise animation.
[Drag field] Velocity influence	How strongly the drag force is influenced by the particle velocity.
[Drag field] Size influence	How strongly the drag force is influenced by the particle size.