US Patent 8666119 Geometry tracking

A first frame includes a first 2D image of a motion capture subject in the real 3D space. A 3D model is deformed into a first deformation and placing the deformed 3D model in a virtual 3D space in a first location so that the deformed 3D model corresponds to the first 2D image. A second frame includes a second 2D image of the motion capture subject in the real 3D space. 2D changes in the second 2D image relative to the first 2D image are tracked. The 2D changes are projected on the virtual 3D space as 3D constraints. Based on the second 2D image, the 3D model is again deformed into a second deformation and placing the 3D model in the virtual 3D space in a second location in conformance with the 3D constraints.