Implements an automatic keyframe selection algorithm which uses
couple of approaches to find out best keyframes candidates:
- First, slightly modifier Pollefeys's criteria is used, which
limits correspondence ration from 80% to 100%. This allows to
reject keyframe candidate early without doing heavy math in
cases there're not much common features with first keyframe.
- Second step is based on Geometric Robust Information Criteria
(aka GRIC), which checks whether features motion between
candidate keyframes is better defined by homography or
fundamental matrices.
To be a good keyframe candidate, fundamental matrix need to
define motion better than homography (in this case F-GRIC will
be smaller than H-GRIC).
This two criteria are well described in this paper:
http://www.cs.ait.ac.th/~mdailey/papers/Tahir-KeyFrame.pdf
- Final step is based on estimating reconstruction error of
a full-scene solution using candidate keyframes. This part
is based on the following paper:
ftp://ftp.tnt.uni-hannover.de/pub/papers/2004/ECCV2004-TTHBAW.pdf
This step requires reconstruction using candidate keyframes
and obtaining covariance matrix of 3D points positions.
Reconstruction was done pretty much straightforward using
other simple pipeline routines, and for covariance estimation
pseudo-inverse of Hessian is used, which is in this case
(J^T * J)+, where + denotes pseudo-inverse.
Jacobian matrix is estimating using Ceres evaluate API.
This is also crucial to get rid of possible gauge ambiguity,
which is in our case made by zero-ing 7 (by gauge freedoms
number) eigen values in pseudo-inverse.
There're still room for improving and optimizing the code,
but we need some point to start with anyway :)
Thanks to Keir Mierle and Sameer Agarwal who assisted a lot
to make this feature working.
Made it so reconstructed scene always scaled in a way
that variance of camera centers is unity.
This solves "issues" when different keyframes will
give the same reprojection error but will give scenes
with different.scale, which could easily have been
considered as a bad keyframe combination.
This change is essential for automatic keyframe
selection algorithm to work reliable for user.
There're some features planned which would
require rigid registration, but this code
would need to be re-done anyway to use new
minimizer and solving some issues with ICP
algorithm there.
Several major things are done in this commit:
- First of all, logic of modal solver was changed.
We do not rely on only minimizer to take care of
guessing rotation for frame, but we're using
analytical rotation computation for point clouds
to obtain initial rotation.
Then this rotation is being refined using Ceres
minimizer and now instead of minimizing average
distance between points of point of two clouds,
minimization of reprojection error of point
cloud onto frame happens.
This gives quite a bit of precision improvement.
- Second bigger improvement here is using bundle
adjustment for a result of first step when we're
only estimating rotation between neighbor images
and reprojecting markers.
This averages error across the image sequence
avoiding error accumulation. Also, this will
tweak bundles themselves a bit for better match.
- And last bigger improvement here is support of
camera intrinsics refirenment.
This allowed to significantly improve solution
for real-life footage and results after such
refining are much more usable than it were before.
Thanks to Keir for the help and code review.
This version of libmv includes new gflags and glog libraries which makes
it possible to compile libmv with clang compiler.
Also remove code from CMakeLists which was disabling libmv if using clang.
Tested on linux with gcc-4.6 and clang-3.0, windows cmake+msvc and scons+mingw.
Could be some issues with other platforms/build system which shall be simple to resolve.
===========================
Commiting camera tracking integration gsoc project into trunk.
This commit includes:
- Bundled version of libmv library (with some changes against official repo,
re-sync with libmv repo a bit later)
- New datatype ID called MovieClip which is optimized to work with movie
clips (both of movie files and image sequences) and doing camera/motion
tracking operations.
- New editor called Clip Editor which is currently used for motion/tracking
stuff only, but which can be easily extended to work with masks too.
This editor supports:
* Loading movie files/image sequences
* Build proxies with different size for loaded movie clip, also supports
building undistorted proxies to increase speed of playback in
undistorted mode.
* Manual lens distortion mode calibration using grid and grease pencil
* Supervised 2D tracking using two different algorithms KLT and SAD.
* Basic algorithm for feature detection
* Camera motion solving. scene orientation
- New constraints to "link" scene objects with solved motions from clip:
* Follow Track (make object follow 2D motion of track with given name
or parent object to reconstructed 3D position of track)
* Camera Solver to make camera moving in the same way as reconstructed camera
This commit NOT includes changes from tomato branch:
- New nodes (they'll be commited as separated patch)
- Automatic image offset guessing for image input node and image editor
(need to do more tests and gather more feedback)
- Code cleanup in libmv-capi. It's not so critical cleanup, just increasing
readability and understanadability of code. Better to make this chaneg when
Keir will finish his current patch.
More details about this project can be found on this page:
http://wiki.blender.org/index.php/User:Nazg-gul/GSoC-2011
Further development of small features would be done in trunk, bigger/experimental
features would first be implemented in tomato branch.
