A Critique of Structure-from-Motion Algorithms

How an object appears in an image is determined in part by interactions with other objects in the scene. Occlusion is the most obvious from of interaction. Here we present a system which uses 3D CAD models in combination with optical and range data to recognize partially occluded objects. Recognition uses a hypothesize, perturb, render, and match cycle to arrive at a scene-optimized prediction of model appearance. This final scene-optimized prediction is based upon an iterative search algorithm converging to the optimal 3D pose of the object. During recognition, evidence of terrain occlusion in range imagery is mapped through the model into the optical imagery in order to explain the absence of model features. A similar process predicts the structure of occluding contours. Highly occluded military vehicles are successfully matched using this approach.