Function factories that return functions to standardize rotation angles to specific angle ranges.
angle_halfcircle_bottom()angle_halfcircle_right()
angle_fixed(theta = 0)
angle_identity()
Fixed angle, in radians.
angle_halfcircle_bottom() standardizes angles to (-pi/2, pi/2].
angle_halfcircle_right() standardizes angles to (0, pi].
angle_fixed() sets all angles to a fixed value (0 by default).
angle_identity() does not modify any angles.