1. A method for automatic initialization of 2D to 3D image registration, comprising: acquiring a 3D model; calculating a plurality of shape descriptor features from the acquired 3D model representing a plurality of poses of the 3D model; acquiring a 2D image; matching the plurality of shape descriptors to the acquired 2D model; determining an optimum pose of the 3D model based on the matching of the plurality of shape descriptors to the acquired 2D model; and generating an initial registration, in an image processing system, between the 3D model and the 2D image based on the determined optimum pose.