Need to Understand 2D Cell Rotation Angle When Cell is Mirrored About the Y-axis

Hi All,

I have a program that needs to unrotate a 2D cell to 0 deg/no reflection which has been placed at any rotation angle and/or mirrored about the X- and/or Y-axis.

Specifically, the problem I'm having is when the cell has been mirrored about the Y-axis, mdlRMatrix_toAngle () returns a rotation angle of 180 deg from the cell's rotation matrix, which causes the cell to be unrotated by and incorrect angle.  mdlTMatrix_containsReflection () (get tMatrix from rMatrix) does return TRUE which does indicate the mirroring. When the cell is unrotated by the inverse of its rMatrix, it get a 180 deg rotation that messes up its orientation.

Is there way to understand the 180 rotation angle and contains reflection mirroring from mdlTMatrix_containsReflection() information to properly unrotate the cell? 

communities.bentley.com/.../Cell-2D-Rotation.dgn

Regards,
Warren

v8i SS10, VS2005, W10