Pablo wrote: > The best way to speed up the optimisation is to exploit the problem > structure when doing the optimisation. Currently a general purpose > nonlinear least square minimiser is used in libpano. > This is very inefficient for large problems where the variables are only > sparsely connected. A sparse levenberg marquardt algorithm would work > wonders there. > There is a fast implementation for 3D reconstruction problems that could > be adapted to optimize panoramas http://www.ics.forth.gr/~lourakis/sba/. > However, it is too inflexible (all pictures can only have the same > number of parameters, no linking of parameters possible) for use within > hugin or libpano.
Pablo, may you interpret some more detail on this topic? For example, what you mean that the sba is too inflexible (all pictures can only have the same number of parameters, no linking of parameters possible) for use within hugin or libpano? When reading some scholar papers on panoramic image stitching like [1]*, I always find that they use the Bundler Adjustment (BA) to solve for all of the camera parameters jointly. And I think the BA is the essential step for the camera parameters optimization. Libpano use a more general purpose nonlinear least square minimizer (more specially, the Levenberg-Marquardt algorithem) to solving the camera parameters instead of the BA, so what is the difference between the LM and BA? The sba[2]* package is the open source implementation of the generic Sparse Bundle Adjustment, if it counld be adapted to use in libpano, the optimization process can be speed up. And, I find that the Photo tourism[3]* project by Washington university grail group also use the sba[2]* to solve camera parameters, and they release their modified version named Bundler[4]*. [1]* Automatic Panoramic Image Stitching using Invariant Features. M. Brown and D. Lowe. International Journal of Computer Vision. 74(1), pages 59-73, 2007. [2]* sba: http://www.ics.forth.gr/~lourakis/sba/index.html [3]* Photo tourism: http://phototour.cs.washington.edu/ [4]* Bundler: http://phototour.cs.washington.edu/bundler/ -- Yili Zhao -- You received this message because you are subscribed to the Google Groups "hugin and other free panoramic software" group. A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/hugin-ptx
