I'll revive this thread, because I'm trying to achieve the same thing and it seems not possible yet.
I'm trying to 'get' whether the reference line is in the inside or outside face. The "Is flipped" global variable doesn't achieve much, and the ac_wall_direction_type still behaves the same. Returns 0 if ref line is inside or outside, returns 2 if ref line is centered and 1 if it is flipped regardless of inside/outside, not solving the issue.
Any possible way to achieve this?
WALL_MAT_A is the inside face material of the wall if ac_wall_direction_type is 1 or 3 (consistent with WALL_FLIPPED = 1). ac_wall_direction_type doesn't reflect which side of the wall is the reference line, it tells which side of the wall is the inside face relative to the reference line's direction (whether WALL_MAT_A or WALL_MAT_B is the inside face).