1. A method of converting 2D video to 3D video using 3D object models, comprising: obtaining a 2D video; defining a 3D space associated with a scene in said 2D video; obtaining a 3D object model of an object viewable in said scene; identifying one or more frames in said scene, each containing an image of at least a portion of said object; defining a position and orientation of said 3D object model in said 3D space that aligns said 3D object model with the image of said at least a portion of said object in a frame of said one or more frames; generating a depth map associated with the frame from said 3D object model positioned and oriented in said 3D space; assigning depth values in said depth map to other elements in said scene; generating a stereoscopic 3D image pair from the frame and from said depth map.