ReadonlydensityMass per unit volume (§25).
ReadonlyfrictionCoulomb friction coefficient (§25).
ReadonlyrestitutionRestitution (§25).
Optional ReadonlyrollingRolling resistance (§25), present only when the material specified one.
Optional ReadonlyspinningSpin resistance (§25), present only when the material specified one.
A §25 PhysicsMaterial as JSON; see the module header on identity.