Hi Martin, Thanks for the explanation.
I confirm that reducing the maximum error helps to remove the artefacts. WIth 0.5 mm I could still see them at one particular zoom level, but with 0.4 mm it was completely gone. Thanks a lot, Andreas On Tue, 8 Dec 2020 at 13:15, Martin Dobias <[email protected]> wrote: > Hi Andreas > > The artifacts you are seeing are caused by the fact how the Entwine tool > works in the default configuration. When creating the octree index of point > cloud data, points are organized in a hierarchy of nodes (each containing > usually tens of thousands of points), with each level of the hierarchy > having smaller bounding volume and higher density. One optimization that > Entwine does is that if child nodes contain a small amount of points, they > get merged into the parent node in the hierarchy - in the hope this will > lower the number of nodes and therefore also the number of requests that > need to be done. See Entwine configuration [1] for more details - > especially the options like minNodeSize, maxNodeSize, overflowDepth, > overflowThreshold. So the artifacts could be simply fixed by reindexing the > dataset with modified configuration. > > All that said, maybe none of that is necessary: > 1. I would suggest lowering "Maximum error" in Layer styling to e.g. 0.5 > mm or even 0.3 mm (assuming the default point size of 1mm) - this should be > giving you a rendering result with very little holes - it is much nicer to > look at and the artifacts should be gone at all scales (it will increase > the rendering time, but I think it is worth it and I think we should lower > the default maximum error - the higher maximum error was initially used > mainly as a debugging tool for us to see if the point spacing in the > rendered map matches the expectations) > 2. For indexing of point clouds, we will be internally using Untwine [2] - > a newer approach (also coming from friends at Hobu!) that has different > configuration and probably won't be showing these artifacts. Peter is > currently working on the integration [3] > > Regards > Martin > > [1] https://entwine.io/configuration.html > [2] https://github.com/hobu/untwine > [3] https://github.com/qgis/QGIS/pull/40404 > > > On Tue, Dec 8, 2020 at 10:30 AM Andreas Neumann <[email protected]> > wrote: > >> Hi, >> >> When testing the 2D point cloud renderer I noticed that in certain scales >> / zoom levels one can clearly see point cloud tile borders: >> >> see screenshot at >> https://www.carto.net/neumann/temp/point_cloud_artefacts.png >> >> There seem to be different densities involved in certain regions here, >> but clearly they correspond to tile borders. >> >> Is this an expected artefact? Can this be avoided? >> >> When I zoom in or out, these artefacts seem to disappear. >> >> Thanks and greetings, >> >> Andreas >> >> >> _______________________________________________ >> QGIS-Developer mailing list >> [email protected] >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer >> > _______________________________________________ > QGIS-Developer mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer > -- -- Andreas Neumann QGIS.ORG board member (treasurer)
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