[ 0.4, 0.4, 0 ];
    Debug.pnt.add( Ref.target, 0xff0000, 1.5 );

    // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    const bLen = 0.3
    const arm  = new Armature();
    arm.addBone( 'bone0', null, null, [0,0,0] );
    arm.addBone( 'bone1', 0, null, [0,bLen,0] );
    arm.addBone( 'bone2', 1, null, [0,bLen,0] );
    arm.addBone( 'bone3', 2, null, [0,bLen,0] );
    arm.addBone( 'bone4', 3, null, [0,bLen,0] );
    arm.bind( null, bLen );

    const pose = arm.newPose();
    pose.updateWorld();

 