Do you know of a method, algorithm, software or approach to remove internal points from a dense pointcloud. I'm interested in keeping the points on the (outer and inner, i.e., holes or indentations) boundary of the object. The points/vertices in the point cloud are available with values for their X, Y and Z coordinates.
My previous approach includes facet ambient occlusion in Meshlab, but this works only on facets, not vertices.
Thank you very much in advance.
What you seem to require is some kind of 3D alpha-shape based concave hull algorithm.
I would look at the PCL as well as the CGAL library for implementations. I know the concept started in 2D but CGAL has 3D alpha shape implementations on which good concave hull algorithm can be build. I know PCL has a 2D implementation but maybe they also have something for 3D point clouds.
See the following references:
https://www.codeproject.com/Articles/1201438/The-Concave-Hull-of-a-Set-of-Points
https://doc.cgal.org/latest/Alpha_shapes_3/index.html
https://github.com/mapbox/concaveman
https://stackoverflow.com/questions/24682250/creating-3d-alpha-shapes-in-cgal-and-the-visualization
http://graphics.stanford.edu/courses/cs268-11-spring/handouts/AlphaShapes/as_fisher.pdf
Thank you Bruno, for these valuable pointers. I don't think that constructing the concave hull will work, as the object to reconstruct contains internal structures, such as through-holes, that should be kept in the reconstruction and the concave hull would eliminate these by reconstructing the object's boundary.
The Alpha Shape reconstruction on the other hand, seems promising. Such a reconstruction is possible in MeshLab. Unfortunately, it does also reconstruct some internal structure that I don't want to reconstruct, e.g. artifacts. I'll experiment with MeshLabs Ambient Occlusion (AO) for a bit more to see if these structures can be remove programmatically.
Cheers
Felix
Hello Felix,
If you could post some snapshots of the kind of structures you are talking about, I would like to see that.
Good luck
Felix,
I don't know if it's possible to you/your Institution but try to get a better software to deal with the point cloud, i.e. Geomagic.
Anyways, it is not possible to you to delete those points manually? Going through a noise reduction, outliers, determining specific filters...
Post some snapshots for us to see clearly what's going on with your cloud.
Good luck!
Cheers!
Hello Thiago,
thank you for the suggestion. I'd rather solve this problem programmatically or with the use of open source software as it is supposed to end up in an (open source) service.
Attached are two screenshots, with the first (point.png) showing the object and its composing points. The internal points are visible.
The second screenshot shows the Alpha Shape reconstruction, which did not work as expected, as internal points were mistaken for structural information.
Cheers
Felix
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