Forces & collisions
Push your simulation around with force fields, and give it something to bump into with colliders.
A simulation on its own just falls under gravity. Force fields shape how things move — wind, swirls, attraction, turbulence. Colliders give your particles, cloth, and bodies something solid to land on, slide along, and pile up against. Both feed the same solver, so they stack together naturally.
Force fields
The simulation.force_field node makes a force you can wire into a simulation. Pick a type:
Directional — a uniform push in one direction. Wind, or an extra gravity override.
Point — pull toward (or push away from) a single point. An attractor or repulsor.
Vortex — spin everything around an axis. Good for tornadoes, whirlpools, swirling sparks.
Turbulence — procedural noise that jitters and churns. Drift, smoke wisps, organic chaos.
Drag — slows things down based on how fast they're moving. Air resistance, thickening the "feel" of a fluid.
Each field has a falloff so its strength fades with distance: None, Linear, Quadratic, or Smooth. Add several fields and they combine — wind plus turbulence plus a point attractor all act at once.
| Parameter | Type | Default |
|---|---|---|
force_type | String | "Directional" |
direction_x | Number | 1 |
direction_y | Number | 0 |
direction_z | Number | 0 |
strength | Number | 50 |
position_x | Number | 0 |
position_y | Number | 0 |
position_z | Number | 0 |
radius | Number | 0 |
falloff | String | "None" |
noise_amplitude | Number | 0 |
noise_frequency | Number | 0.010 |
noise_speed | Number | 1 |
Drag is the one field that reacts to velocity rather than position. Reach for it when a sim feels too "floaty" or you want particles to settle instead of coasting forever.
You can use up to 16 force fields at once, with up to 8 of those being Drag fields. Gravity itself is just a built-in Directional force, so it counts as one of your fields under the hood.
Forces from a Volume
A Volume that holds a 3D vector per cell can drive a simulation too — wire a vector Volume into the simulation's input and it acts as a spatially-varying force, like a baked wind map or a curl-noise field. This is great for art-directed flow that changes from place to place. See Volumes for making Volumes.
Volume forces currently push particles, not 6-DOF rigid bodies. Per-Volume strength controls are coming; for now sensible defaults apply.
Colliders
A collider is something your simulation can't pass through. Add a Physics Collider node with a built-in shape — box, sphere, convex hull, or the mesh itself — and wire it into your simulation alongside the bodies. Cloth drapes over it, particles pile against it, rigid bodies bounce off it.
The simulation also has a built-in ground option so you don't need a separate floor collider for the common case.
Colliders use friction (how much things grip versus slide) so you can tune anything from ice to sandpaper.
Anti-tunnelling is always on, so fast-moving objects won't shoot straight through a thin collider. There's no setting to fuss with — it just works.
Distance Field colliders
For collision against arbitrary, complex shapes — not just the basic primitives — you can use a Distance Field as a collider. Wire a Distance Field Volume into the simulation's input and it becomes a static collision boundary that follows the exact contours of your shape.
The collider must be a true Distance Field — something that knows how far every point is from a surface — not a plain density or fog Volume, which has no surface to collide against. If you only have a density Volume, derive a Distance Field from it first (DNA can extract one from the volume's surface). See Distance fields & volumes.
Collision layers
Sometimes you don't want everything colliding with everything. Collision layers let you control which groups of objects interact. Put your character bodies on one layer and the debris on another, and you can have the debris collide with the world but pass right through the character — or any combination you like.
See also
Simulation — simulation overview
Particles · Cloth · Hair · Rigid bodies
Queries (sim-free) — raycasts and overlap checks against colliders
Distance fields & volumes — Distance Fields and Volumes
Fields & sampling — driving parameters from spatial fields