how to convert the CGAffineTransform to CGTransform3D?

how to convert the CGAffineTransform to CGTransform3D?

I use UIImagePickerController as the Camera Controler. and i add a 3d layer on the upper of the camera view.

then when i want to add a 3d model to the 3d layer . i muset set the 3d scene campera projection matrix . and model view matrix.

but the UIImagePickerController just have a CGAffineTransform .