// if motor is working to leave the limit, we need an extra
// velocity constraint to model the motors contribution at the limit
if ( motorTargetVelocity>0 && motor>0) {
extra.assign(
b1, b2,
new Vector3(), b1.isFixed()? new Vector3():b1.state.inverseinertia.multiply(axis), new Vector3(), b2.isFixed()? new Vector3() : b2.state.inverseinertia.multiply(axis.multiply(-1)),
new Vector3(), axis, new Vector3(), axis.multiply(-1),
0,
this.motor,
null,
this.velocity-this.motorTargetVelocity, 0 );