Soft bodies
Squishy, jiggly objects that deform on impact and spring back — and hold their volume while they do it.
A soft body takes a solid mesh and lets it wobble, dent, and bounce like jelly, rubber, or a stress ball. Unlike cloth, which is a thin surface, a soft body has insides: it tries to keep its shape and its volume even as it gets squashed.
What makes it squishy
The Soft Body Sim node turns an incoming mesh into a deformable body and runs it on the GPU. Two things keep it feeling solid:
Shape springs along the mesh edges resist stretching and tearing, so the surface holds together.
Volume / pressure keeps the interior from collapsing — squash one side and the rest bulges out, like air trapped in a balloon. Turn pressure up for an inflated, bouncy feel; turn it down for a denser, doughier one.
Wire a mesh into the node, drop it into your simulation, and press play. The mesh deforms when it hits the floor or a collider, then settles back toward its original shape.
Start with a mesh that has a reasonable, even amount of detail. Very sparse meshes have little to deform; extremely dense ones cost more to cook every frame. A medium-resolution sphere or character is a good first test.
Putting it in a scene
Soft bodies live in the same simulation world as everything else. Feed your soft body, any simulation.rigid_body objects, and your colliders into the simulation, and they all interact in one solve — a soft ball will bounce off a static floor and get knocked around by falling rigid blocks.
Add gravity, ground, and obstacles the usual way (see Forces & collisions). Forces like wind or attractors from a simulation.force_field push on a soft body just like anything else.
| Parameter | Type | Default |
|---|---|---|
input | CollectionOf(Geometry) | — |
pin_group | String | "" |
iterations | Number | 10 |
stretch_compliance | Number | 0 |
volume_compliance | Number | 0 |
shape_stiffness | Number | 0.100 |
damping | Number | 0.010 |
strength | Number | 1 |
Tuning the feel
A few controls shape the whole personality of the body:
Stiffness — high values snap firmly back to the rest shape (rubber); low values stay floppy and slow to recover (memory foam).
Pressure / volume — how hard the interior resists being squashed. This is the dial that separates a beach ball from a bean bag.
Damping — how quickly the jiggle dies down. Low damping keeps it wobbling for a long time; high damping settles it fast.
Iterations / substeps (on the simulation) — raise these if a fast or heavy body looks rubbery, passes through colliders, or jitters. They cost more to cook, so only push them as far as you need.
If a soft body explodes, sinks through the floor, or quivers in place, it usually means the motion is too fast for the solver to keep up. Increase substeps first, then iterations, and check that your collider is actually a solid surface and not a thin shell.
Soft bodies vs the alternatives
Want a thin flapping surface (a flag, a cape)? That's Cloth.
Want a body that keeps a fixed shape and only rotates and slides? That's a rigid body — see Rigid bodies.
Want strands (hair, rope, grass)? See Hair.
Soft bodies sit in the middle: they keep their volume but still deform.