Well, I guess the atom describing the next leg defines the eligible directions. One could define the smallest deflection as forward. If I am not mistaking this would mean that transitions from one oblique atom to another would use the corresponding element from the set of eight, oblique to orthogonal would go along the largest coordinate, and oblique to diagonal would stay in the same quadrant. Other transitions would all be 'degenerate', i.e. 'forward' would indicate two symmetry-equivalent continuations of orthogonal or diagonal atoms, wheter this continuation is of the opposit kind or oblique.
Well, I guess the atom describing the next leg defines the eligible directions. One could define the smallest deflection as forward. If I am not mistaking this would mean that transitions from one oblique atom to another would use the corresponding element from the set of eight, oblique to orthogonal would go along the largest coordinate, and oblique to diagonal would stay in the same quadrant. Other transitions would all be 'degenerate', i.e. 'forward' would indicate two symmetry-equivalent continuations of orthogonal or diagonal atoms, wheter this continuation is of the opposit kind or oblique.