Up: Stereo Geometry
When objects are viewed from two different positions, it is highly likely that some areas are occluded, thus these areas are only seen by one camera.
The detection of occluded areas is an important problem in stereo vision and complicates the generation of 3D data. Figure 2.9 depicts this situation. The left camera is not able to see what is directly situated on the right side of the object. The same situation occurs for the right camera on the left side of the object. In Figure 2.9 only a small area is occluded, but when the object would be translated more into the view of the right camera the left camera may not see the object at all. This would be the worst case scenario, but it illustrates the influence of occlusion, especially concerning the correspondence analysis. For occluded areas, no depth value can be computed.