Force fields
Invisible fields that push, pull, swirl, or roughen nearby particles, with per-emitter routing so each field affects only what you want.
Open in the interactive manual →The interactive version has full-text search, a table of contents, and light/dark themes.
A force field influences particles within its radius: to swirl a cloud, suck it inward, blow it sideways, or rough it up. Add one with Create ▸ Force Field, then tune it in the Force Field section of Properties.
Field types
| Type | Effect |
|---|---|
| Vortex | Particles swirl around the field's axis. |
| Gravity well | Pulls particles inward toward the center. |
| Wind | Pushes particles in one direction. |
| Turbulence | Adds chaotic curl-noise jitter. |
| Pointer | The visitor's own cursor or finger. Moving or dragging pulls particles toward it and blows them along the direction of travel at the same time; a click or tap sends a ripple expanding outward from that spot. |
| Camera | The visitor themselves. Particles are shoved aside as the camera moves through them and settle again the moment it stops, so dust parts around someone walking through it. |
Aim a Wind or Vortex field by rotating the node: both use its local +Y axis. In the editor a field draws as a translucent sphere of influence (with an arrow for Wind/Vortex) so you can see its reach.
The Pointer field
This is the one field a visitor drives. It never steals the click, so orbiting, links and tap actions all keep working exactly as they did.
A cursor is a ray and a force needs a point, so you choose the depth it lands at with Cursor depth: Facing the viewer puts it on a plane through this node that always faces the camera (reachable anywhere on screen), and Flat, at this node's height puts it on a horizontal slice, drawn as a ring, for effects on a floor or a table. Either way the node's position is what sets that depth, so it is still worth placing.
- Magnet and Drag wind both multiply Strength. Set either to 0 to use only the other: magnet alone is a cloud that follows the cursor, wind alone is a wake that only appears while you move.
- Settle is how fast particles shed the speed this field gave them. Lower for a loose, floaty trail; higher for a tight cloud stuck to the cursor. At 0 nothing ever settles, so a long visit ends with everything either collapsed on the cursor or blown out of frame.
- Ripple push, Ripple speed and Ripple width shape the tap. Ripple push 0 turns taps off entirely. A ripple always finishes expanding even after the finger lifts, and retires once it reaches the field's Radius.
The Camera field
The other field a visitor drives, and the only one that needs no input device at all: it works for someone carried through a scene on a phone joystick, where there is no cursor to move. Particles are pushed away from where the camera is, plus a share of the way it is travelling, scaled by how fast it's going.
- Sweep splits that push. At 0 particles are shoved straight outward from the camera; at 1 they're swept along its direction of travel. The default (0.35) is the mix that reads as getting out of the way rather than exploding on approach. The two halves always sum to one, so turning Sweep up doesn't also turn the whole field up.
- A parked camera exerts nothing. Stop moving and the field stops entirely, which is both what looks right and why it costs nothing while a visitor stands and reads. A field that kept pushing would slowly empty a room of its own dust.
- The node still decides where the effect applies: its Radius is measured from the node as usual, so a field placed in one room leaves every other room's particles alone while the visitor flies past.
It's the cheap way to make a room feel occupied: one dust emitter, one Camera field, and the motes part as anyone walks through them.
Field controls
- Field active: uncheck to switch the force off while keeping the node where it is. This is the control that turns a field on and off; the outliner eye only hides its gizmo, and particles keep feeling a hidden field.
- Radius: the sphere of influence.
- Strength: how hard it pushes. Negative strength inverts the field: gravity repels, wind reverses.
- Falloff: Constant, Linear, or Inverse-square across the radius.
- Frequency: turbulence only; the scale of the noise.
Affinity routing
By default a field affects every emitter in the scene. But each emitter has a Force-field affinity control (it appears once a field exists): uncheck "Affected by all fields" and tick only the fields you want this emitter to feel. So one vortex can spin your sparks while leaving the smoke alone.
Affinity is also the lever that keeps fields cheap, and scene weight prices it that way. A field draws nothing, but every active field is another pass over every particle of every emitter it reaches, every frame, so the cost lives in that pairing rather than in the field itself. Routing one emitter to one field is charged as one field; leaving everything on "all fields" in a scene with a dozen fields is charged as a dozen. A field switched off with Field active costs nothing, and Pointer and Camera fields are charged at half, since both stop entirely while the visitor is standing still.