The main thing is to find some direction that the curve will never be parallel to - that is what you said as the ‘up dir’. The system right now needs some ‘fixed’ direction that it will point the ‘up’ vector towards.
The main thing is to find some direction that the curve will never be parallel to - that is what you said as the ‘up dir’. The system right now needs some ‘fixed’ direction that it will point the ‘up’ vector towards.