narf and kdtree flann search

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Hi,

I'm not sure if I should ask this here or in the PCL mailing list but I'll ask here anyways.

I am trying to use kdtree_flann to match narf descriptors. I am extracting the descriptors in a similar way to the NARF PCL tutorial. The problem is when I try perform the NN search between two pointclouds (pointcloud A added as the input and point cloud B used as the query), all the features in B match to the same feature in A. The distances reported by kdtree are all 0 (zero).

• I noticed that narf36 has a {x,y,z,roll,pitch,yaw} value which are all 0 (zero) for my features, is this why all my distances are zero when kdtree performs its search?

The .descriptor values themselves are different for each feature in A and B. I would have expected that kdtree would use the Narf::getDescriptorDistance function or something similar to compute the distances.

• Does anyone know what distance metric it uses when you provide the PointCloud< Narf36 > as the data type to kdtree?
• And is there a way to change this (to maybe even a custom distance function)?

Thanks in advance, - Joe