The extraction of marker points from image sequences is
related to the reconstruction problem, which is to identify
the 2D points in two images that are projections of the
same 3D point in the world. From corresponding points
within the image sequences the relative orientation and
the 3D positions of the corresponding points can be estimated.
Once we have determined the relative orientation,
additional 3D points can be easily extracted from
two 2D points in the image sequence, as illustrated in
Figure 3. In VR Modeler we distinguish between a semi
automatic and a fully automatic marker point extraction.
The semi automatic extraction is supported over an incremental
and straightforward process by a human operator.
Consequently the user defines marker points in the image
sequence over a simple point and click interface with
subpixel accuracy by zooming into the images.