It is convenient to introduce intermediate "fictitious" frames that each vary from the previous frame by a simple rotation.
Frame B is rotated about +(az> = bz>) by an angle H, frame C is rotated about -(bx> = cx>) by an angle L, and frame D is rotated about +(cy> = dy>) by an angle theta.
Use the mouse to manipulate the camera.
Use the control box to move each frame.