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Handling Occlusions

There are different types of occlusions which may arise when a scene is scanned with a laser beam or structured light sensor. Lots of these occlusions are not resolvable without domain specific knowledge, or models, helping to derive structural interpretation of the images. For this work, we only consider indoor scenes containing mostly man-made objects, for which both general architectural and scene specific knowledge might be available.

Previous research on occlusion reconstruction focused on the reconstruction of a single large area occluded by one object. In that context two cases were considered: Occlusions Preserving Surfaces, Occlusion Breaking Surfaces.

In both the above cases the occluding object does not obscure the boundaries of the occluded one. The work of [9] explored the case when the occluding part partially obscures boundaries of an occluded object. This case is called Occlusion Breaking Boundaries. The corner area of a cupboard occluded by an open door, as in figure 1, is an example of this case. Figure 2.c shows an example of these occlusions.

  figure47
Figure 2: Type of occlusions

In order to reconstruct occlusions we need to exploit available information that constrains a scene. In particular:

1) good surface continuation. That is, the occluded surface keeps the same shape of its visible part [8, 12].

2) good boundary continuation. That is, the occluded boundary keeps the same slope of its visible part.

3) architectural constraints. That is, the occluded surface is bounded by an architectural constraint. This can be a wall, a floor, a door, a window etc. [3, 7].

The reader should note that in order to solve cases of Occlusion Preserving Surfaces and Occlusion Breaking Surfaces, the surface good continuation constraint suffices. In the proposed case of Occlusion Breaking Boundaries it is also needed to apply the constraint of good boundary continuation and the architectural constraints.


next up previous
Next: Occlusion Understanding Up: Occlusion Understanding and Recovery Previous: Introduction

Bob Fisher
Thu Jan 17 16:45:14 GMT 2002