CGAL users discussion list

[Simon Giraudot <>]

Hello,

Region Growing can be quite long as it implies neighbor queries on 
pretty much all data points: if the cluster_epsilon parameter is very 
large, then these neighbor queries can take a very long time. But 5 days 
still seem like a crazy runtime to me: are you sure you are compiling in 
Release mode? CGAL can be very slow without the compiler optimizations.

Apart from that, I would strongly advise tuning the parameters by hand, 
especially cluster_epsilon. You can maybe use a factor of either:
- the average spacing: 
https://doc.cgal.org/latest/Point_set_processing_3/group__PkgPointSetProcessingAlgorithms.html#gae7d0d1063bcebb7f8a1b0f90597c423b
- the global scale: 
https://doc.cgal.org/latest/Point_set_processing_3/group__PkgPointSetProcessingAlgorithms.html#gafbe157053a3e1c4f545a99dc55a425cb

Also, I would make some trials on a small subset first (and check if the 
output is what you expect) to avoid wasting hours or computation.

Note that in the most recent version of CGAL (4.12 beta), a callback 
mechanism was introduced in Region Growing so that the user can know the 
advancement of the algorithm while it's running: 
https://www.cgal.org/2018/02/27/cgal412-beta1/

Best,

--
Simon Giraudot, PhD
R&D Engineer
GeometryFactory - http://geometryfactory.com/


Le 06/03/2018 à 08:03, williamlai3a a écrit :
> Hi all,
>
> I am running Region_growing to detect only plane on a 3.7 Million point
> cloud.
> I just call using .detect() so it uses the default parameters.
>
> The detection function has been running for 5 days on single CPU and never
> ending.
> (I dunno how to make it utilize my CPU resource as it does not have
> concurrent flag)
>
> Are there any possibilities that the .detect() function comes to a dead
> loop?
> Or it is just taking very long time to end?
> Would that be parameters problem? like min_points?
>
> Any ways to make the algo run faster?
>
> Thank you very much.
>
>
>
> --
> Sent from: http://cgal-discuss.949826.n4.nabble.com/