Compression of the Concentric Mosaic
Figure 1. Capturing device of the concentric mosaic.
This project is for the compressing and browsing
of virtual environment.
The concentric mosaic is an easy way to represent
a realistic environment. The capturing facility of the concentric mosaic can
be shown in Figure 1. We just rotate a single camera at the end of a level beam,
with the camera pointing outward and shooting images as the beam rotates. The
resultant dataset is a video sequence. For a typical realistic environment with
large depth variation, 900 to 1500 shots have to be captured in a circle to
render the scene properly without alias. This leads to a dataset of several
hundreds of megabytes.
Figure 2. Rendering of concentric mosaic
Rendering the concentric mosaic involves reassembling
slits from existing photo shots. No 3D or depth information of the scene is
needed to reconstruct a novel virtual view of the environment. Shown in Figure
2, let P be a novel viewpoint and AB be the field of view to be rendered. We
split the view into multiple vertical slits, and render each slit independently.
Let the slit PV be a rendered slit. We simply search for the slit P'V in the
captured dataset and use the content of P'V to replace PV, where P' is the intersection
between ray PV and the camera path. The basic hypothesis here is that the intensity
of any ray does not change along a straight line unless blocked. Therefore,
what is rendered at PV can be recovered from that is observed in P'V.
For application of the concentric mosaic, the large
dataset has to be efficiently compressed. Moreover, since only a portion of
the data is used to render each concentric mosaic view, it is imperative that
the compressed data to be formed in an indexable fashion. That is, portion of
the compressed concentric mosaic should be accessed and delivered in a timely
Existing researches on concentric mosaic can be
classified into 3 categories, block coder, reference frame coder and 3D wavelet
coder. I have written a survey paper on the subject, and it can be found below.
I have also investigated efficient reference frame coder and 3D wavelet coder.
If you are interested in our work, please follow the link.
©Copyright by Jin
Li, June 22, 2001