public VerletParticle3D clearVelocity() { prev.set(this); return this; }
public VerletParticle3D setPreviousPosition(Vec3D p) { prev.set(p); return this; }
protected void applyForce() { temp.set(this); addSelf(sub(prev).addSelf(force.scale(weight))); prev.set(temp); force.clear(); }