Near-Plane Clipping Problem when using external import model as a mirror(oblique faces)

We can know from the source code,mirrors rotation info which from mirror’s worldmatrix will be used to construct the Near cut face in cameras projectMatrix.
I met difficulty when I use an external model in FBX format,whose mirror mesh is a oblique plane with oblique normal,but it’s worldMatrix rotation is (0,0,0),and the woodybracket behind the mirror can not be correctly culled. What can I do to correct?

Sry, I’m afraid I don’t understand your problem. Can you please explain in more detail?

Thank you!Sorry for my bad English
Please look at these picture,and maybe you can get my question
image image