[Vxl-users] Can any one give any advices on my experiment,;) ?

[Xiaowei Li <ne...@bi...>]

Hi,Everyone=A3=A1

=09I'm a new comer to VXL, and I wanna use it in my multiple view=
 geometry applications, since VXL seems having more expansibility=
 and easier implementation of many prevailing algorithms. I write=
 this mail to see whether you can give some ideas on my=
 experiments.

=09One key issue in my experiment is to track a planar target in=
 image sequences. The plane would be identified at the first=
 frame, by drawing on that image a region inside which is rightly=
 the main portion of the plane. After this, the tracking is=
 absolutely automatic. Homography(H) between consecutive images=
 would be computed with RANSAC. According to the Multiple View=
 Geometry theory and the RANSAC method, this H's computation=
 would result in a robust estimation of H and a set of 2D point=
 correspondences as inliers, and of course these corresondences=
 are on the plane. "Extending" the region a bit more in the=
 previous image,making correspondences from the extended region=
 of the previous image to the consecutive image, and now using=
 the computed H to test these new correspondences, we could=
 verify which are the ones on the same plane, and furtherly a=
 rough boundary of that plane is obtained in the latter image.=
 Doing this in every frame, thus the plane is tracked robustly. 

=09That's the method. I think when we assume that no too large=
 occlusions enter that plane, this tracking would be sufficiently=
 robust. Do you think so?

=09But I meet some problems in the implementation, because of my=
 unfamiliarness to the VXL environment.

=09The first thing is to identify the plane by drawing a geometric=
 region in the 1st frame. The common geometric objects which=
 could represent the ROI in VXL are always simple rectangles=
 ,circles, or ellipses. How to represent more general objects in=
 VXL, such as regions needed in our experiment with free curves=
 as boundary, or polygons ?

=09The second thing is to make correspondences. The first step to=
 use RANSAC is to get putative correspondences based on proximaty=
 and similiarity of their intensity neighbourhood. When we've=
 already got two sets of Harris points, one set for each image of=
 a image pair, how to match them ? Does there exist an=
 off-the-shelf class to achieve this in VXL ?

=09Next thing is the robust estimation. I found that in the Robust=
 Estimation Library, the minimization of some objective functions=
 is also based on RANSAC sampling, not based on traditional=
 derivative analysis, Isn't it? Can this offer the same accuracy=
 ?

=09The final thing is about the XCV. I think this is very useful=
 for me. I don't know whether anyone is still working on its=
 updation. If you do this work, can you mail me a newly version=
 of XCV, with source code,please ?

=09Thank you very very much for your help !
=09=09

Best wishes,

Shawrie Lee(Xiaowei Li)
AR Lab, BIT, P.R. China
ne...@bi...
TEL:+86 10 6891 2565
2004-10-13