Surface Force
Pull particles onto an object's surface, or a set distance off it, from inside or out: they hold there, ride it as it moves, and slide along it.
Pull particles to an object's surface, or a set distance off it, from inside or out, over a response time: they hold there, going with it as it moves, and slide along it as they would.
- Add it
- EventAdd OperatorForcesSurface Force
- Sends on
- Nothing: it has no wire.
- Influence
- Yes: it does as much as a value says, particle by particle (0 none, 1 all of it).
When to use it
- Clinging: ants, sparks or water drops crawling over a moving character.
- A shell: particles hovering a little off a surface, as a glow or a force field (Offset above 0).
- Wrapping: particles flowing over and round an object rather than bouncing off it.
Unlike Goal, it's a force: particles slide along the surface as their other forces push them, bump into things, and don't each have a set place.
Settings
As the flow editor’s sidebar shows them. Changing any of them marks the bake old; those marked Keyframable can also change through a bake.
About how long it takes them to settle: no less smoothly, but no further than they must.
One of the flow’s number values, to weigh it by, particle by particle. Empty for all of it, on all of them. See Influence.
Each step, particles are pulled toward the nearest point of the surface (or Offset out from it), like a spring that never overshoots, over about the Response time. They come with the surface as it moves and deforms. Along the surface, they go as their other forces take them.
Particles on the back of the faces go through to the front, so the faces' direction matters: recalculate normals (ShiftN in Edit Mode) if they cling to the inside.
Reach fades it out to nothing this far from the surface (0: everywhere), so only particles that come near are caught. Most caps how much it changes their velocity in a second (0: no cap), so fast particles can tear free.
Works with
- Turbulence or Flock to move them over the surface.
- Drag to keep them from sliding too freely.
- Influence: weighed by a value, it pulls each particle that share as hard.
Problems you may see
event: operator: 'object' has no surface
Errors stop a bake; warnings don’t. Every message is on the Messages page.
Related
Goal
Send each particle to its own target on an object or on another event's particles, arriving on time and smoothly: to form text, a logo or a mesh, hold it, then let go.
Particle Physics
Make particles solid balls that bump into each other, roll, pile up and come to rest: sand, grains, gravel, beads and ball pits.