Mesh edges rounding

[map IQ]

Hi Daniel/all!
I'm looking to extract precise edges of concrete slabs from a TLS scan - I've tried:
- extract points by normal change rate
- extract upper sections, sample the sections with dense points, then 2.5d mesh (poisson doesn't work very well with sectioned pointclouds I'm finding)
- mesh normally at 12-16 octree, dirichlet boundary, 1 samples per node, point weight 0, linear fit. This tends to round off corners, no way to get it to pick the higher edge points.

None of these methods provide the best available edge from the data. The closest to a true edge seems to be from extracting upper-biased cross sections and then sampling points from them, but there doesn't appear to be a way to turn these cleaner datasets into clean edges.

Any tips on methods that could get me nice edges?

[daniel]

How have you computed the normals? I'm a bit surprised that Poisson smooths them that much. Well, it always smooths things a little bit, but not to this extent. Or maybe, since the normal computation is based on an average, it fails to generate properly oriented normals. That's always a challenge.