User Forum of Software BASEMENT

JonasStuder

User

From: Bern

Registered: 2019-02-19

Posts: 5

Grid Generating with BASEmesh - Problems with Quality meshing

Dear Basement community,

I just started using Basement and finished the Tutorials. Now I’m trying to run a model with my own data. I managed to generate the elevation model but I have some problems generating the quality mesh: 

I have a question concerning grid generation (for 2D). I try to generate a Quality Mesh. As input I only use a model boundary and breaklines (as shown in figure 1). The breaklines represent streets, buildings and other breaklines. Different to the tutorials, the polylines are not always closed to a polygon. When I’m running the Quality Mesh tool (as shown in figure 2) after a while several error messages appear (see figures 3 and 4). The “.node”-file does not exist in the folder (see figure 5). The figure 6 shows the information from Basemesh after the error occurred.

Is it possible to use such breaklines which doesn't build closed polygons?
I don’t know how to solve this problem and would be happy for some advice.

Thanks
BR,Jonas

Last edited by JonasStuder (2019-04-03 13:10:10)

Dominik

User

From: Bern

Registered: 2018-09-26

Posts: 19

Re: Grid Generating with BASEmesh - Problems with Quality meshing

Hi Jonas,

I had the same problem a few times. Most likely the breaklines that reach the polygon exceed the outer boundary. Try to use the clip tool provided by QGIS (sometimes that does not solve the problem) or use the clip tool from ArcGIS. This should solve the issue.

It does not matter that lines laying within the polygon do not touch the boundary.

Cheers Dominik

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Dominik Vogt
MSc Student Institute of Geography University of Berne

JonasStuder

User

From: Bern

Registered: 2019-02-19

Posts: 5

Re: Grid Generating with BASEmesh - Problems with Quality meshing

Thank you for your answer!

The Breaklines are already clipped with the boundary. I clipped them again to be sure-but the error still occurs.
I also ran the program as administrator with the same result.

Has someone another idea?
Thanks

Stephan Kammerer

Developer

Registered: 2015-03-31

Posts: 67

Re: Grid Generating with BASEmesh - Problems with Quality meshing

Your breaklines look super detailed. I don't know, where you get this breaklines from, but generally I would say that it is not advisable to just import every breakline from a CAD plan. First check which breaklines are really necessary. Breaklines should be defined at distinct terrain transitions like dam crests or embankment bases.Furhtermore you need breaklines to define holes. In my opinion it does not make sense to define breaklines for every street (to what end?)
In case your breakline layer consits of features (line segments) that are too close to each other, triangle might not be able to execute the mehsing.
So I would suggest that you "clean" your breakline layer and only use those, which are really necessary to represent your domain at a reasonalbe degree of abstraction.

Dominik

User

From: Bern

Registered: 2018-09-26

Posts: 19

Re: Grid Generating with BASEmesh - Problems with Quality meshing

You might further try the tools 'Check Validity' and 'Simplify' in QGIS in the Tab Vector --> Geometry tools.

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Dominik Vogt
MSc Student Institute of Geography University of Berne