[WIP] Adding a VLFeat-compliant feature descriptor #167
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Description
All of PopSift's earlier descriptors were created by reading the Lowe paper again and again, attempting to understand how the descriptors should be implemented. We still believe that we followed the letter of the text, but apparently not the spirit.
Both Changchang Wu's implementation and VLFeat compute the descriptors differently. Furthermore, VLFeat's descriptors are rotated by a quarter circle compared to Changchang Wu's. This descriptor follows the VLFeat interpretation because it is the one that has been used by default in AliceVision.
Features list
Implementation remarks
At this point, the default PopSift behaviour is still to use our old interpretation. It is faster but obviously not exactly in the spirit off Lowe's idea. If this PR is accepted, should the default be vlfeat for compatibility reasons?