Google's Ceres Solver released as open source

[Keir Mierle]

At long last, Google's bundler is now open source:

http://code.google.com/p/ceres-solver

And, don't forget to upvote us to get some traffic:

http://www.reddit.com/r/programming/comments/t1mo7/ceres_solver_googles_large_scale_nonlinear_least/

http://news.ycombinator.com/item?id=3914951

I'm currently polishing up the Windows uport, then while in Holland I'll get it integrated into libmv (and Blender).

Keir

[François T.]

sweeet :) 

2012/5/1 Keir Mierle <mie...@gmail.com>

Keir

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[Jesse Vander Does]

I downloaded and compiled ceres.  I have some questions about the "simple bundle adjuster" and the BAL data set that you guys might be able to answer.

First off, the BAL data format.  I can see that the first part of the file contains image correspondence by defining a:

<camera index> and <2d point index> and then its <img x> <img y>.

After that the BAL website confuses the hell out of me.   

<camera_num_cameras>

<point_1>

...

<point_num_points>

Can anyone explain what these single values are?  The second question is this.  Does the example bundle adjuster take 2d correspondence and calculate fully calibrated cameras?

Regards,

Jesse

Jesse Vander Does
401-226-8251 | jvand...@gmail.com

[Sameer Agarwal]

<point_1> is the first 3d point

<point_2> is the second 3d point and so on

followed by each of the cameras in order.

The points are 3 vectors, one entry per line.

The cameras are 9 vectors, one entry per line, corresponding to their 9 degrees of freedom, 3 for translation, 3 for rotation, 1 focal length and 2 radial distortion.

The bundle adjuster takes the correspondences and initial estimates of the 3d points and cameras and computes refined estimates. This is not a full sfm system so it does not compute them from scratch from the correspondences.

Sameer

[Jesse Vander Does]

Thanks for the instant response! I now see how the file contains estimated 3d points and cameras.  I had thought these were required for bundle adjustment but  wasn't seeing them represented in the file.

Can you comment on how accurate the initial estimates need to be for the system to converge on something reasonable?

[Keir Mierle]

+ceres-solver, in case other people were wondering about this.

Keir

[Sameer Agarwal]

Jesse,

 

Can you comment on how accurate the initial estimates need to be for the system to converge on something reasonable?

This is very hard to say and depends on the actual scene configuration.

Sameer