Physics

Gravity

StrengthDefault: 9.81

Magnitude of gravitational acceleration applied to the grains. A value of 9.81 approximates Earth's gravity when one scene unit represents one meter. A value of 0 disables gravity.

DirectionDefault: 0.0, 0.0, -1.0

Direction of gravitational acceleration. Strength controls its magnitude.

Friction

Particle FrictionDefault: 0.5

Resistance to sliding between grains in contact. Higher values increase grip between grains. A value of 0 allows frictionless sliding.

Dynamic ScaleDefault: 0.8

Friction while sliding as a proportion of static friction. Lower values let grains slide more easily once motion begins. A value of 1 gives equal sliding and static friction.

Friction VariationDefault: 0.0

Varies friction between grains, giving some more grip than others. Higher values increase the variation. The random pattern stays consistent when the amount changes.

Accurate FrictionDefault: On

Resolves friction throughout the constraint solve, helping grains resist unwanted sliding and maintain stable piles. Adds calculation time.

Drift ThresholdDefault: 0.0

Suppresses grain movement below this speed to reduce slow drift while still allowing grains to respond to forces and collisions. Higher values can suppress intended slow movement.

Stability

Mass ShockDefault: Off

Helps piles stay stable and reduces the “decompression” effect where they slowly loosen or spread after settling. Grains lower in the direction of gravity yield less during contact corrections, supporting those above without changing their actual mass. The effect is inactive when gravity is zero.

Shock StrengthDefault: 1.0

Start at 1.0 and increase gradually if the pile still settles too much. Higher values provide stronger support but can make impacts look less natural. Set to 0 to disable the effect. Reset and resimulate to compare changes.

Global DampingDefault: 0.0

Reduces all grain velocities each frame. The effect accumulates over time, so even small values can noticeably slow the simulation's motion.

Max Collision SpeedDefault: 0.0

Limits the velocity change caused by collision and constraint corrections per substep. Zero disables the limit. A lower nonzero limit can tame sudden bursts, but may prevent grains from fully clearing a collider.

Use modest changes and compare fresh runs. Damping suppresses motion everywhere; it is not a substitute for enough solver substeps. Mass Shock changes contact weighting, not the physical grain mass.

Rest

Freeze At RestDefault: Off

Holds settled grains in place to eliminate residual movement. Frozen grains can wake when disturbed by collisions or nearby active grains.

Rest ThresholdDefault: 0.05

Maximum movement per frame, as a fraction of Grain Radius, for a grain to be considered settled. Higher values allow grains to freeze sooner.

Start Asleep and Wake Radius are in the Activation panel. Freeze At Rest holds grains that settle during the simulation.

Plasticity

Shape Retention works with or without glue. Unglued material uses temporary bonds; glued material changes bond rest lengths. These material controls can be animated; see Animation & keyframes.

Shape RetentionDefault: 0.0

Controls how strongly the material retains deformation after being stretched or compressed. Higher values let it adopt new shapes more readily and reduce recovery toward its original shape. Works with or without glue.

Bond ReachDefault: 0.5

Distance over which loose grains can form temporary bonds for shape retention. Higher values allow bonds between more distant grains. Applies only to grains without glue bonds.

Bond BreakingDefault: 0.5

Controls how easily temporary shape-retention bonds break as grains separate. Higher values make bonds break with less stretching. Applies only to grains without glue bonds.

Advanced PlasticityDefault: Off

Enables separate controls for when deformation becomes permanent, how quickly it sets, how much it recovers, and how far it can change the material's shape.

FirmnessDefault: 0.56

Amount of stretching or compression required before deformation begins to set. Higher values allow more deformation before the material adopts a new shape.

Set SpeedDefault: 0.38

How quickly deformation sets after the Firmness threshold is exceeded. Higher values set deformation faster. At 0, new deformation stops setting while Bounce Back, Plastic Damping and existing bond support remain active.

Bounce BackDefault: 0.5

How quickly bond rest lengths return toward their original lengths, including when Set Speed is 0. Works with glue and temporary shape-retention bonds. It does not restore broken bonds or guarantee the original overall shape.

Dent LimitDefault: 0.58

Limits how far bond rest lengths can change from their original lengths as deformation sets. Higher values allow greater permanent deformation.

Plastic DampingDefault: 0.0

Reduces oscillation in bonds undergoing plastic deformation. Higher values reduce springy motion while the material changes shape.

Bond Reach and Bond Breaking appear when Shape Retention is greater than zero. Advanced Plasticity exposes the separate sliders and a readout of yield stretch and how much a short impact will set. Increasing Set Speed makes deformation become permanent more quickly.