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https://github.com/liangfu/python-sba

Python port of http://www.ics.forth.gr/~lourakis/sba
https://github.com/liangfu/python-sba

bundle-adjustment

Last synced: 18 days ago
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Python port of http://www.ics.forth.gr/~lourakis/sba

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README 

        
===============================================================

Python wrapper for Lourakis' sparse bundle adjustment C library 

===============================================================



Enjoy! The most recent version can be obtained from bitbucket via::



    hg clone ssh://[email protected]/devangel77b/python-sba



As prerequisites, you will also need to install the sba library as a shared object (libsba.so) (Makefile with shared object target included here) and the sba projections library (libsbaprojs.so)::



    http://www.ics.forth.gr/~lourakis/sba

    https://bitbucket.org/devangel77b/libsbaprojs



See HOWTO.txt for details. 



Typical usage

=============



The main way to use this is as follows::



    import sba



    cameras = sba.Cameras.fromTxt('cams.txt')

    points = sba.Points.fromTxt('pts.txt',cameras.ncameras)

    newcams, newpts, info = sba.SparseBundleAdjust(cameras,points)



If you wish to alter the default and autodetected options, you can

create an Options object and change it, and then pass it to sba::



    options = sba.Options.fromInputs(points,cameras)

    # can also update options.XXX to appropriate values

    newcams,newpts,info = sba.SparseBundleAdjust(cameras,points,options)



Hopefully this is cleaner than the original way to call it in C. 



Helpful Hints

=============



Some users have used this package in a workflow combined with the CalTech

Borguet camera calibrations and with data exported from Hedrick's Matlab 

dltDV5 / easyWand5 tools.  If decomposing someone else's P matrix for use

as a cams.txt, it may help to remember that rotations and translations here 

are in the world frame; Rc=R', Tc-R*t (using notation of Hartley and 

Zisserman).



When building for a Mac, one user (amin_abouee) noted that the extensions 

should be .dylib rather that .so; this can be fixed by altering the lines 

in both the Makefiles and the code, e.g.:



    libsba = ctypes.CDLL("libsba.dylib")



On rotations: AndyLJones noted the following "SBA works with two sets of rotations. There's the initial rotations, which are fed in as part of the globs argument of sba_motstr_levmar_x and family in libsba. These are fixed throughout the optimization. There're also the "local rotations", as Lourakis's readme calls them, which are fed in with the rest of the camera parameters via the p argument to the same function. These are updated at each step. Internally, libsba uses local_rotation * initial_rotation when figuring out the projections." This becomes important if you are working on a known-rotation problem and wish to specify initial rotations. See Issue #16 for more detail. 



    

Contributors

============



The original sba C library was written by Manolis Lourakis and is 

described in Lourakis, Manolis I A and Antonis A Argyros (2004), "The design 

and implementation of a generic sparse bundle adjustment software package 

based on the Levenberg-Marquardt algorithm", FOURTH_ICS TR-340.



If using this package in research work, we would appreciate you citing it: D Theriault, N Fuller, B Jackson, E Bluhm, D Evangelista, Z Wu, M Betke, and T Hedrick (2014). A protocol and calibration method for accurate multi-camera field videography. J exp Biol 217:1843-1848. The BibTeX entry is::



    @article{Theriault:2014,

      author = {Theriault, D and Fuller, N and Jackson, B and Bluhm, E and Evangelista, D and Wu, Z and Betke, M and Hedrick, T},

      title = {A protocol and calibration method for accurate multi-camera field videography},

      journal = {J exp Biol},

      doi={10.1242/jeb.100529},

      year = {2014},

      volume = {217},

      pages = {1843--1848}

    }



Thanks also to

==============



Manolis Lourakis and Antonis Argyros, Ty Hedrick, Evan Bluhm, my mom and the academy. Version 1.6.5 has bug fixes from Isaac Yeaton and Nick Gravish, and notes on Mac usage from Amin Abouee. Andy Jones helped provide clarification on rotations in known-rotation problems.