about profile of tunnel

I just figured it out why my mnt_polar depth code failed to calculate tunnel profile directionally. The reason is the given tunnel profile. The walls are absolutely vertical and in my code, when I check if a point is in a triangle, I just check z direction. If the wall is vertical, the function will fail to tell the point is in triangle. The solution is simple, just implement more planes, ie., projections on x and y. Thus the problem is solved.