Abstract: In this paper we present a method for automatically constructing a CAD model of an unknown object from range images. The method is an incremental one that interleaves a sensing operation that acquires and merges information into the model with a planning phase to determine the next sensor position or "view". This is accomplished by integrating a system for 3-D model acquisition with a sensor planner. The model acquisition system provides facilities for range image acquisition, solid model construction and model merging: both mesh surface and solid representations are used to build a model of the range data from each view, which is then merged with the model built from previous sensing operations. The planning system utilizes the resulting incomplete model to plan the next sensing operation by finding a sensor viewpoint that will improve the fidelity of the model. Experimental results are presented for a complex part that includes polygonal faces, curved surfaces, and large self-occlusions.