Adds Dense SIFT feature type. http://www.vlfeat.org/overview/dsift.html

[sashichandra]

No description provided.

[sashichandra]

Hi, vl/dsift.h is already present in opensfm/src/third_party/vlfeat/vl/dsift.h They are not part of this pull req.

…

-sashi.

On Fri, Apr 20, 2018 at 8:39 PM, Russ ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In opensfm/src/dsift.cc <#236 (comment)>: > @@ -0,0 +1,52 @@ +#include "types.h" +#include "dsift.h" + +#include <vector> +#include <iostream> + +extern "C" { + #include "vl/dsift.h" Are these files included in the pull req? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#236 (review)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/Af6yBm19FiMlzHaRQAvhcVcqlfAf-KCaks5tqqnqgaJpZM4QVw9n> .

[russkel]

Hi @sashichandra, sorry I deleted my comment after I found the file.

[russkel]

Is there a chance you could resolve the conflict in the features.py file @sashichandra ?

@paulinus are you willing to merge this? Otherwise I'll pull this into my own working copy.

[paulinus]

@russkel, I've resolved the conflicts on this branch and put the result in this branch https://github.com/paulinus/OpenSfM/tree/sashichandra-dsift

About merging it to master, the main concern is that Dense SIFT is not a suitable feature for SfM in general. The reason for that is that it extracts features on a fixed grid that is not adapted to the actual image texture. As a result, corresponding features in different images are not centered around the same real-world point. This adds substantial error to triangulation and resection algorithms to the point where they no longer work.

Testing this branch on berlin and lund dataset, I was unable to get good reconstructions. Only berlin yield a reasonable reconstruction after setting dsift_step to a small number so that the discretization error was reduced. That produced a lot more features which were then slow to match.

If there is a trick to make things work better, please let me know.

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