clusters within clusters+tips please :)

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AlanRoberts
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clusters within clusters+tips please :)

Post by AlanRoberts » Mon Mar 20, 2017 11:34 am

After some advice and maybe a few tips
Have scanned a large building, interior and exterior, and aligned scans, have clusters for each floor, with 5 or 6 clusters within each floor, have manualy picked correspondences and have green lights for all, but while picking corresponding objects between clusters it always shows a red light, but when placing clusters everything is green and ok is this normal?

also, having a setup of a cluster for each floor, with 5-6 clusters within, would I be better off moving all clusters to 1 master (all interiors) cluster or have many parent children clusters, if that makes sense, is there any benefit either way.
finally
exporting the whole finished point cloud to recap, any tips, reducing point (subsample) cloud etc, final output will be floor plans, x-sections and maybe 3d model (BIM possibly)

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gmwalker
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Re: clusters within clusters+tips please :)

Post by gmwalker » Tue Mar 21, 2017 6:23 am

Clusters is absolutely the best way to manage large sites. I have completed many building surveys with many levels of parent/child clusters.

I've personally found that C2C works well for clusters of up to 10-20 scans max. Any more and you start to get outlier scans that become problematic.

Also, C2C for clusters generally works well, but again once you get to the final stages of bringing a handful of clusters together with many child clusters and scans within, I have found it more accurate and timely to choose some key pairs of scans within the clusters to manually identify correspondences (plane fits seem to work best, much better than the point selection approach) and then use the Target Based solution to get the final solution. So long as you have decent overlap (with decent overlap between scans being lesson 1.01 for scanning) then getting some well orientated correspondences shouldn't be an issue and as soon as you have a plane fitted to the x, y and z axis they should automatically start identifying themselves as matches that you can them force to lock in.

Words of caution though! Make sure you generate scan point clouds at the first pre-processing stage so that once you have a registered cluster you can check the quality of the overlap using Correspondence View with Clear View turned on. I have had green lights on many occasions where the actual solution has had some mis-matches present. Likewise, do this also for Target Based solutions from manually identified correspondences to check the solution; sometimes the results despite being green will show one or two identified correspondences with larger residuals, I then experiment with removing these to see if the plane fit was compromised in some way and reassess the solution. Also always check the histograms, these are hidden in the report under the old interface but they are still very powerful in giving an idea on the quality of the registration, particularly C2C solutions.

As far as the exporting and importing into RECAP, you can't really decimate the export from Scene. You can on import into RECAP but isn't really worth it as the file size savings are minimal from my experience. Best approach is to generate the RECAP file and then export an RCS file from RECAP; here you can apply a decimation that will have significant impact on file size and can make working within Revit or other Autodesk programs much easier due to the small file sizes, plus if you find you need more resolution in a particular area you can go back and use the RCP version. Both RCS and RCP attach very easily and play nicely with Autodesk.

AlanRoberts
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Re: clusters within clusters+tips please :)

Post by AlanRoberts » Tue Mar 21, 2017 5:39 pm

Many thanks Gmwalker
Looks like i have been doing most things in a very similar way as you suggest, only have one minor issue with a very small room that the entrance doubles back on itself, so having a hard time finding decent correspondences ( that are not to close together) otherwise all seems good. Thanks for the tips on recap, I prefer doing all my cleanup in that, much more user friendly, and like isolatiog points rather than deleting, at least in the first instance of cleaning up.
have been checking the graphs and using clear view a lot, best 2 tools for checking and I did go a little overboard with overlap, as I hadnt done a job of this size before, beter safe than sorry
any way thanks for all the tips appreciated
cheers
Alan

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