The Space Envelope: A Representation for 3D Scenes

This work introduces the space envelope, a shape model based upon a boundary description. Instead of modeling a single object (or solid), a space envelope encloses a volume of empty space. The advantage is that in any given view, there may be any number of objects, this number being di cult to determine from pixel-data alone. However, there is always one, and only one, volume of visible empty space. Once a model has been constructed de ning the space envelope, higher-order operations may be applied to reason about the scene's content. For instance, surface geometries and topology could yield insight into the number of visible objects. The enclosed empty volume may also be used for vision-based navigation (known free-space), while the surfaces are used for view correspondences. Algorithms to automatically construct a planar boundary representation (b-rep) space envelope from a range image are presented. Results for testing the algorithms on over 400 images from four di erent range cameras are presented. 2