blender/extern/libmv/ChangeLog

commit e3b2bccba6145290738a6677c14f7369ec7a38cd
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Apr 4 02:59:58 2013 +0600

    Suppress strict compiler warnings in glags/glog libraries

commit 5fca459adcf0a3419fa9cd8d983dc2c952d02647
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Apr 4 01:20:18 2013 +0600

    Lint cleanup, mostly white space and line width.
    
    Also moved own includes to the top of files.
    
    Should be no functional changes :)

commit 9a9dd458a622928b91dbd3c79900577923283838
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Mar 29 00:20:29 2013 +0600

    Fix for TransformTracks in uncalibrated pipeline
    
    Transformation matrix was completely ignored by
    TransformTracks() and final marker coordinate
    exactly matched it's source coordinates.
    
    Seems to be just a typo in vector usage: need to
    use "b" (which is transformed one) instead of "a"
    when converting projective coordinate to 2D space.

commit d35766cc9901609e32f4d80faba715695bea3c40
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Mar 29 00:19:11 2013 +0600

    Revert part of e2eb58c4230f94ef0c72fb4005e5434088d52e80
    
    That commit included one change which shall have been
    go as separate commit with more detailed description.

commit e8d71b4e96fd78eb60773b6557d66da672e65753
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Wed Mar 27 20:37:05 2013 +0600

    Silenced more warnings
    
    - Added includes of own header to fast implementation files.
    
    - Camera intrinsics wouldn't complain about unknown pragma when
      building without OpenMP support.
    
    TODO: Make it a CMake option to build libmv with OpenMP support.
    	  Currently multi-threaded intrinsics only available when
          using custom CMake rules for bundled libmv version
          (as it's done in Blender).

commit ad442812654f270dc088394410fda1b81b8dc450
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Wed Mar 27 20:18:51 2013 +0600

    Multithreaded camera intrinsics
    
    Implemented multithreaded buffer (un)distortion
    for camera intrinsics using OpenMP.
    
    By default, (un)distortion is single-threaded,
    but it is possible to as CameraIntrinsics to
    use more threads by calling SetThreads method.

commit c88b4881096174a16a9f9e6fc2c9dcad3e255b25
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Wed Mar 27 18:45:09 2013 +0600

    Movie functions implementation from panography header
    into own CC implementation file.
    
    Before this all panography functions were declared as
    static, which is not so much useful from re-useability
    point of view.

commit 2d2faf9104bc035722cff6775e1b8e7c93143aba
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Wed Mar 27 18:37:36 2013 +0600

    Build shared Ceres library only if BUILD_SHARED_LIBS is enabled

commit daa3ddd3260ccaf2bf9c72eadb89213d91e549ec
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Wed Mar 27 18:21:52 2013 +0600

    Update Ceres to upstream version 1.5.0

commit cf5dc678878345ea3f221ce50cb2b9e539c2ab38
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Wed Mar 27 15:06:24 2013 +0600

    Code cleanup: removed more deprecated FFmpeg API usage
    
    This time in qt-tracker application.

commit e2eb58c4230f94ef0c72fb4005e5434088d52e80
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Mar 26 17:19:51 2013 +0600

    Code cleanup: silent unused variables warnings

commit af89bb24667e39b7e655173ea807fdcfbeef4422
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Mar 26 16:54:14 2013 +0600

    Code cleanup: no need to declare empty body for ProgressUpdateCallback:invoke
    
    Make force this method to be overridden by derivative classes.
    Also removed currently unneeded callbacks.cc.

commit 0441d4ee06fad0219256a5704f931eec916a3868
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Mar 26 16:37:27 2013 +0600

    Code cleanup: silent type narrowing in qt-tracker

commit cd4b61c976448d0fdedefb3ed4b21d70e078f94b
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Mar 26 16:26:39 2013 +0600

    Changes to unit testing
    
    - Move ceres test binaries to ${LIBMV_TESTS_OUTPUT_DIR}/ceres,
      so they don't mess with libmv's application binaries and
      tests.
    
    - Removed ceres_ prefix from ceres unit tests, only use this
      prefix for targets (targets need to be unique name).
    
    - Added unit tests data for ceres, otherwise system_test fails.
    
    - Restored "test" makefile target.

commit cf704ada08acc8b26167e7bfb3e1e88fd278de23
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Mar 26 15:01:15 2013 +0600

    Code cleanup: use rw-rw-r-- mode for source files

commit 64b31e3e43acb52aaf6f591b9d1c2449bf6ef3bd
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Mar 26 14:57:46 2013 +0600

    Code cleanup: don't use deprecated FFmpeg API functions

commit 2a3676499548ad5dba5a5c5eadf3bb71e640b612
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Mar 5 17:40:52 2013 +0600

    Switch from DENSE_NORMAL_CHOLESKY to DENSE_QR
    
    DENSE_QR is better behaved numerically and after recent
    changes from Sameer there's no big difference in speed.

commit bcb920df02133da5b7e55fbc74edb9222004eecc
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Mar 5 17:15:43 2013 +0600

    Update Ceres to 1.5RC3
    
    It brings optimization of DENSE_QR and DENSE_SCHUR solvers.

commit 473996468a4e67e7c860169181a4ff31ce9b8c80
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Mar 1 17:44:54 2013 +0600

    Fixed incorrect order of arguments passing
    to EXPECT_EQ in keyframe selection tests.

commit d38ebb74693fdf5b8f0fecf62a3d8c9c53b0b84a
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Mar 1 17:40:38 2013 +0600

    Modal (aka tripod) solver rework
    
    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!

commit 5d6c2e7a27bdd1a1b23bf289d70a9b8f62514c9a
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Mar 1 17:37:35 2013 +0600

    Increase verbosity level for reprojected markers info
    
    This information is useful, but in cases when you, say,
    working on a bundler it's annoying to scroll all the
    information up.

commit ac252bb1250b3028b9c94736b644e7ab4e7b14b8
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Mar 1 17:36:19 2013 +0600

    Move radial distortion code to own templated function
    
    This shall not lead to any functional changes, just
    avoids radial distortion code duplicated in camera
    intrinsics and bundling code.
    
    For fancier bundle adjustment support of  different
    distortion models this is not actually enough and
    would need to make some bigger changes, but this
    changes makes code a bit easier to maintain already.

commit c253b794612dd529e1d3a9bd7a7c41c32c9a9abb
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Mar 1 17:33:27 2013 +0600

    Use threaded cost function, jacobian and linear solver
    computation, so bundling is as fast as it could be with
    current parameter block structure.

commit 931fe37a10212b91b525d4f6eb753990a338b471
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Mar 1 17:29:21 2013 +0600

    Fixed comment for euclidean bundling,
    which is now supports raidal bundling independently
    from other intrinsics.

commit 217d8e6edc3de1a853fb84275d2d2dd898e7529c
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Feb 26 18:19:01 2013 +0600

    Allow K1,K2 refirement combination
    
    It is now possible to refine only radial distortion
    with new Ceres based bundler and this new combination
    is already used in Blender.

commit d8850addc944d400f7a9c358396c437d9e4acc70
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Feb 26 18:17:09 2013 +0600

    Switch euclidean intersection code to use Ceres
    
    Would not expect any significant changes in solver
    behavior, but it could be more accurate in some cases.
    
    Switching projective intersection to ceres is marked
    as a TODO for now.

commit 6990b7946ec96b3cb2dcfc8a1beaaba9538b0802
Author: Keir Mierle <mierle@gmail.com>
Date:   Mon Feb 25 20:00:48 2013 +0000

    Switch motion tracker bundle adjustment to Ceres.
    
    Patch originally written by me, then finished by Sergey. Big
    thanks to Sergey for troopering through and fixing the many issues
    with my original (not compilable) patch.
    
    The Ceres implementation uses 2 parameter blocks for each camera
    (1 for rotation and 1 for translation), 1 parameter block for
    common intrinsics (focal length etc) and 1 parameter block for
    each track (e.g. bundle or 3D point).
    
    We turn on some fancy optimizer options to get better performance,
    in particular:
    
      options.preconditioner_type = ceres::SCHUR_JACOBI;
      options.linear_solver_type = ceres::ITERATIVE_SCHUR;
      options.use_inner_iterations = true;
      options.use_nonmonotonic_steps = true;
      options.max_num_iterations = 100;
    
    Special thanks to Sameer Agarwal of Ceres fame for splitting out
    the SCHUR_JACOBI preconditioner so that it didn't depend on
    CHOLMOD.  Previously we could not use that preconditioner in
    Blender because CHOLMOD is too large of a dependency for Blender.
    
    BundleIntrinsicsLogMessage:
    - Moved bunch of if(foo) LG << "bar" into this function, to make
      EuclideanBundleCommonIntrinsics a little bit easier to follow.
    
    EuclideanBundle:
    - Fix RMSE logging.

commit 1696342954614b54133780d74d6ee0fbcbe224f0
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Tue Feb 26 18:10:33 2013 +0600

    Upgrade ceres to latest upstream version
    
    This is needed because of some features of new Ceres
    for further development.

commit 575336f794841ada90aacd783285014081b8318c
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Mon Jan 7 15:58:40 2013 +0600

    Fixed for keyframe selection
    
    - Calculate residuals for GRIC in pixel space rather than
      in normalized space.
    
      This seems to be how it's intended to be used.
    
      Algebraic H and F will still use normalized coordinates which
      are more stable, after this matrices are converted to pixel
      space and Ceres refinement happens in pixel space.
    
    - Standard deviation calculation was wrong in GRIC. It shouldn't
      be deviation of residuals, but as per Torr it should be deviation
      of measurement error, which is constant (in our case 0.1)
    
      Not sure if using squared cost function is correct for GRIC,
      but cost function is indeed squared and in most papers cost
      function is used for GRIC. After some further tests we could
      switch GRIC residuals to non-squared distance.
    
    - Bring back rho part of GRIC, in unit tests it doesn't make
      sense whether it's enabled or not, lets see how it'll behave
      in real-life footage.
    
    - Added one more unit test based on elevator scene and manual
      keyframe selection.

commit 24117f3c3fc5531beb6497d79bb6f1780a998081
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Sun Jan 6 19:07:06 2013 +0600

    Added test for keyframe selection based on manual selection
    
    Additional changes:
    
    - Reduce minimal correspondence to match real-world manually
      tracked footage
    
    - Returned back squares to SymmetricEpipolarDistance and
      SymmetricGeometricDistance -- this is actually a cost
      functions, not distances and they shall be squared.

commit 770eb0293b881c4c419c587a6cdb062c47ab6e44
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Fri Dec 21 00:43:30 2012 +0600

    Improvements for keyframe selection
    
    - Changed main keyframe selection cycle, so in cases there're no
      more next keyframes for current keyframe could be found in the
      image sequence, current keyframe would be moved forward and
      search continues.
    
      This helps in cases when there's poor motion in the beginning
      of the sequence, then markers becomes occluded. There could be
      good keyframes in the middle of the shot still.
    
    - Extended keyframe_selection_test with real world cases.
    
    - Moved correspondences constraint to the top, so no H/F estimation
      happens if there's bad correspondence. Makes algorithm go a bit
      faster.
    
    Strangely, but using non-squared distances makes neighbor frames
    test fail, using squared distances makes this tests pass.
    
    However, using non-squared distances seems to be working better
    in real tests i've been doing. So this requires more investigation/

commit 7415c62fbda36c5bd1c291bc94d535a66da896d0
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 20 18:46:09 2012 +0600

    Cosmetic change to correspondences reports in keyframe selection

commit ceaf80c987ec0338e7e83965bc808411453eb755
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 20 18:08:03 2012 +0600

    Various fixes:
    
    - That was a typo in symmetric geometric cost functor, which
      computed inverse distance in a wrong way.
    
    - Fixed compilation of unit tests
    
    - Added simple test for keyframe selection. Currently only
      covers case that neighbor frames with only translation
      (homography should be better than fundamental) are not
      considered a keyframes.
    
      Still need to be investigated why it only works if tracks
      are in pixel space and why doesn't work in normalized space.

commit cfabdfe48df2add3d1f30cf4370efd0b31990ab0
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 20 05:46:53 2012 +0600

    Assorted fixes for keyframe selection:
    
    - Biggest error was in cost functors used for F and H refirement,
      they were just wrong.
    
    - Use natural logarithms, since it's actually makes sense from
      math papers point of view and error is somewhere else.
    
    - Disabled rho for GRIC, for now use non-clamped error for tests.
    
    - Made SymmetricEpipolarDistance returning non-squared distance
      Keyframe selection is currently the only used of this function
      and it seems using non-squared distance makes much more sense.
    
      Also would think to append suffix "Squared" to functions which
      returns squared distances.
    
    - Removed templated version of SymmetricEpipolarDistance, since
      it's not needed actually.
    
    This is actually even worse working than previous implementation,
    but commit it needed for further review.

commit 35d8c57626ad74818f155e6e5960c663ea84e032
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 20 03:00:40 2012 +0600

    Euclidean resection cost function didn't use correct constructor
    
    It was storing a reference to initial rotation passed by value,
    leading to pointer being pointing to a stack variable, leading to
    wrong memory access in residuals computing.
    
    Apparently was visible in optimized builds only with inline
    substitution allowed.

commit 0798d3162bb49cee7e1c423ceccbca1326ad5650
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 20 02:50:52 2012 +0600

    Automatic keyframe selection based on Pollefeys's criteria
    
    This commit implements automatic keyframe selection algorithm
    based on Pollefeys's criteria (F-GRIC is smaller than H-GRIC
    and correspondence ratio is more then 90%).
    
    It is implemented as a part of simple pipeline and returns
    vector of keyframe images for a given Tracks structure.
    
    For simple pipeline reconstruction two best keyframes are
    expected to be selected from all detected candidates.
    Criteria for this selection could be reprojection error of
    solution from two candidate keyfames.
    
    Unfortunately, it's not fully workable yet, hopefully would
    be fixed soon.

commit e943985552f0598ae122252876f305d72c25c2f9
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 6 17:47:11 2012 +0600

    Camera Tracking: allow fallback to reprojection resection
    by user demand
    
    This fixes some "regressions" introduced in previous commit
    which lead to much worse solution in some cases. Now it's
    possible to bring old behavior back.
    
    Perhaps it's more like temporal solution for time being smarter
    solution is found. But finding such a solution isn't so fast,
    so let's bring manual control over reprojection usage.
    
    But anyway, imo it's now nice to have a structure which could
    be used to pass different settings to the solver.

commit 5a23d01dd531d1e0798298d17ba42a3397effb82
Author: Keir Mierle <mierle@gmail.com>
Date:   Thu Sep 20 18:55:44 2012 +0000

    Make Euclidean resection "always" succeed.
    
    The Euclidean resection code had a magical constant, 1e-3, used to
    compare the results of solving an equation. This failure detection
    was well-intended, trying to prevent poor solutions from getting
    made without notifying the caller. Unfortunately in practice, this
    threshold is too conservative. Furthermore, it is not clear the
    threshold should exist at all; the purpose of the Euclidean
    resection is to come up with the best solution it can; other
    methods (e.g. reprojection error) should be used to compare
    whether the method succeeded.
    
    This commit changes the Euclidean EPnP code to always succeed,
    causing the previous fallback to projective resection to never
    run. In most cases, this will result in better reconstructions.
    
    This should, in most cases, fix the dreaded "flipping" problem.

commit 57dad861d2a7f9d058c6d8edde1a2d51d7225a51
Author: Keir Mierle <mierle@gmail.com>
Date:   Thu Sep 20 02:27:34 2012 +0000

    Fix variable naming in the planar tracker.

commit e9392fd3b46f5668662935696e7d9afac3390ca4
Author: Keir Mierle <mierle@gmail.com>
Date:   Thu Sep 20 02:10:33 2012 +0000

    Add smarter tolerance checking in the planar tracker.
    
    The planar tracker uses Ceres for the refinement stage. During
    refinement, Ceres iteratively updates the parameters with the
    latest best guess. If the change in the parameters falls below a
    threshold, Ceres will abort successfully ("converged").
    
    For the case of pure translation tracking, the parameters are
    exactly the two pixel shifts (dx, dy), and measuring the change in
    these parameters gives a meaningful termination criterion.
    However, for all the other parameterizations like affine, where
    the parameterization involves affine parameters that have no
    physical interpretation, Ceres is left with no way to terminate
    the solver early. With the existing code, often many iterations
    are run long after Ceres has found a solution sufficiently
    accurate for all tracking needs. No one needs tracking with
    a quadrillionth of a pixel accuracy; that time is wasted.
    
    This patch extends the existing iteration callback that is passed
    in to Ceres to check if the pattern has fallen out of the search
    window, to also check if the optimizer has made a tiny step. In
    particular, if the maximum shift of any patch corner between two
    successful optimizer steps is less than a threshold (currently
    0.005 pixels), the track is declared successful and tracking
    is terminated.
    
    This leads to dramatic speed increases in some cases, with little
    to no loss in track quality. This is especially apparent when
    tracking patches with affine or perspective motion models. For
    example, on some tracking cases I tried, the iterations Ceres took
    went from 50 to 3.

commit 36729c19bf90cb767e9adb96ba7dd48a5ace2be1
Author: Keir Mierle <mierle@gmail.com>
Date:   Wed Sep 19 22:25:02 2012 +0000

    Detect too-small planar tracking patches.
    
    The planar tracker did not detect very skinny patches which have
    effectively zero area and are untrackable. This adds detection and
    rejection of patterns with zero area. This fixes a crash found by
    during Mango production.

commit 5cf2bae255a5a0f2e36ea0516670782cb88b589d
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 6 17:33:53 2012 +0600

    Real fix for previous commit from Keir. He's comment;
    
    Cleanup for when trackers fall out of the search window.
    
    Sergey originally left a TODO() here, but his fix is the correct
    one. I removed the TODO and fixed some comment issues.

commit a11533918720e5b43dc1e95895db0eb36c8c06aa
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 6 17:31:16 2012 +0600

    Fix crash when tracking in planar motion model (and maybe some other)
    
    It was an Abort() caused by check for solver result not equal to USER_ABORT.
    
    In some cases solver returns USER_ABORT due to BoundaryCheckingCallback
    detects coordinates does not belong to image.
    
    Somehow this callback wasn't called in previous version of Ceres and
    in the same case marker was jumping. Now when the callback is called
    it seems we could simply return failure of tracking without aborting
    Blender.
    
    Probably this is in fact some issue somewhere else, would double
    check with Keir about this.

commit 4be2306bcc664b259aaf7068b9f32ab60124a509
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 6 17:29:39 2012 +0600

    Resolved some compilation warnings (missed prototypes)
    
    In some cases it was missed include of header file, in some other
    cases symbol could be static.

commit bef729ba5c12683d13584d2a728b8b6506b7ca90
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 6 17:27:17 2012 +0600

    Code cleanup: silence some -Wnarrowing warnings from C++11

commit add1415d896818367087c784a3013dd8f1bb2095
Author: Sergey Sharybin <sergey.vfx@gmail.com>
Date:   Thu Dec 6 17:25:18 2012 +0600

    Changes to SamplePlanarPatch to support mask input and
    added output for pattern center.

commit daa354c0735b954b0cd7725626e9a3d67416d46b
Author: Keir Mierle <mierle@gmail.com>
Date:   Sat Jun 9 19:22:39 2012 +0000

    Change libmv's bilinear sampling to assume the same
    pixel conventions as Blender. This fixes the preview
    widget in Blender, and should make tracking slightly
    more accurate.

commit 99b6222873fbfbe248316316956720376a58f438
Author: Keir Mierle <mierle@gmail.com>
Date:   Sat Jun 9 18:58:51 2012 +0000

    Add new warp regularization scheme for planar tracking.
    
    This adds a new term to the tracking cost function that
    restricts how much the optimizer can warp the patch (as
    opposed to merely adjusting the translation). This should
    reduce the "jumpiness" that is sometimes seen when doing
    non-"Loc" tracks.
    
    It is disabled in this commit; a subsequent commit will add
    controls to the tracking dialog for this.

commit a1c5a70badd11cba0470700bad2eac2b2bd30c86
Author: Keir Mierle <mierle@gmail.com>
Date:   Sat Jun 9 06:55:21 2012 +0000

    Planar tracker polish.
    
    - Fixes the correlation checking code that was broken in the
      previous commit. The bug was a transpose error.
    - Fixes a memory leak of the warp functor, found by Sameer.
    - Various cleanups done at Sameer's suggestion.
    
    Thanks to Sameer Agarwal for a code review.

commit 2cb784caa854a77cdd43620ab133f26b87ed0d83
Author: Keir Mierle <mierle@gmail.com>
Date:   Fri Jun 8 17:42:17 2012 +0000

    Make planar tracking much faster.
    
    - This makes planar tracking around 2-3x or more faster than
      before, by rearranging how the sampling is done.
      Previously, the source patch was sampled repeatedly on
      every optimizer iteration; this was done for
      implementation speed, but was wasteful in computation.
    
    - This also contains some additions to Ceres to help
      deailing with mixed numeric / automatic differentation. In
      particular, there is now a "Chain::Rule" operator that
      facilitates calling a function that takes Jet arguments,
      yet does numeric derivatives internally. This is used to
      mix the numeric differentation of the images with the warp
      parameters, passed as jets by Ceres to the warp functor.
    
      There is also a new "JetOps" object for doing operations
      on types which may or may not be jets, such as scaling
      the derivative part only, or extracting the scalar part
      of a jet.
    
      This patche is aimed at Ceres upstream.
    
    - A new function for sampling a patch is now part of the
      track_region.h API; this will get used to make the preview
      widget properly show what is getting tracked. Currently
      the preview widget does not handle perspective tracks.
    
    Known issues:
    
      This patch introduces a bug such that the "Minimum
      Correlation" flag does not work; if it is enabled, tracking
      aborts immediately. The workaround for now is to disable the
      correlation checking, and examine your tracks carefully. A
      fix will get added shortly.