I'm rigging an aircraft for use in Unity 3D and I need to place the object axis i.e. the "center" of each object so that it aligns with things like the edge or a point on the object such as aligning the center with a door edge to make it hinge properly. Is there an easy way to align the object axis with parts of an object, or for that matter the parts of another object? I'm using a plugin to move the axis to the object center, but also need to align it with other parts of the object.