Space Envelope Model Construction

(from range data )

A space envelope model is a CAD-type boundary description. Instead of modeling a single object (or solid), a space envelope encloses a bubble of empty space. The advantage is that in any given view, there may be any number of objects, this number being difficult to determine from pixel-data alone. However, there is always one and only one visible volume of unoccupied space. Once a model has been constructed defining 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.

Similar to an OPUS model , any data for visible portions of the scene are modeled by real surfaces. Any portions of the scene not visible are modeled by occlusion surfaces, representing the boundaries to the as-yet-seen volume of empty space. In the above figure, the same space envelope is shown from three different perspectives. Real surfaces are labeled using letters, while occlusion surfaces are labeled using numbers. Occlusion surfaces 8, 9 and 10 model three of the four boundaries to the field-of-view of the sensor.


In the coming virtual universe, where's all the 3D structural data going to come from? The traditional method is to construct (program) objects and worlds by hand. This work strives towards methods to automatically construct models from image data. For instance, you could walk through your home with a camera, snapping images, feed the images into the model builder, and presto! Virtual reality representation of your home.

Related publications

C code

A tar file containing C code which constructs space envelope models from range images, as reported in the publications above, and as demonstrated below.


Click on any image icon to download the space envelope model in VRML v1.0 format . Occlusion surfaces are shaded in bright greens. Glue surfaces (an artifact of model construction process, usually extremely small) are shaded in bright reds. The boundaries to the field-of-view of the space envelope model are shaded bright blues. Real surfaces use all other colors. Please note that VRML is a developing language, not intended for solid modeling. Webspace will view these models correctly, but you must get inside the model to see it; otherwise, try wireframe viewing.

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The space envelope model / USF /