Optional ReadonlydampingDamping, how much to reduce velocity. Default 0.995 (ie 0.5% loss)
Optional ReadonlylengthLength of 'string' thing is hanging from. If undefined, the current length between thing and pinnedAt is used.
Optional ReadonlyspeedMax speed of swing. Slower speed can reach equilibrium faster, since it might not swing past resting point. Default 0.001.
Pendulum force options