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IFC，CityGML and LOD

1. S by shanmama on 20 Oct 2020, edited 25 Oct 2020 #

   Recently, I was studying the combination of BIM and GIS and came into contact with the concepts of CityGML and LOD.

   I would like to consult professionals: 1. Are there any recommendations for conversion tools between IFC and CityGML? 2. What do you share about BIM+GIS?

2. B by bernd on 20 Oct 2020 # +1 votes

   Same problem here. How to convert a IFC to CityGML?

3. R by ReD_CoDE on 20 Oct 2020 # +1 votes

   This is the problem some work on it :))

   The issue is not on semantics, but in geometries/topologies

   Thomas @aothms has worked a lot in this area

4. S by shanmama on 21 Oct 2020 #

   @bernd said:

   Same problem here. How to convert a IFC to CityGML?

   Yes. I have reviewed some literature and found that many people in academia are trying this problem

5. S by shanmama on 21 Oct 2020 # +1 votes

   @ReD_CoDE said:

   This is the problem some work on it :))

   The issue is not on semantics, but in geometries/topologies

   Thomas @aothms has worked a lot in this area

   thank you very much! Every time I ask a question in my impression, you can give me reasonable enough suggestions.

6. A by aothms on 21 Oct 2020 # +5 votes

   I agree, @ReD_CoDE, with my university I'm working on exactly this. We should be able to release something rather soon under an open source license. It'll be based on a version of IfcOpenShell that uses CGAL in addition to OCCT, https://github.com/tudelft3d/IfcOpenShell/tree/cgal/ which was a monster effort, but is getting near to something usable.

7. B by bernd on 21 Oct 2020 #

   wow thomas what a great news :-)

8. M by Moult on 21 Oct 2020 #

   For the record I think the repo for conversion is here, but it seems a little old :) https://github.com/tudelft3d/ifc2citygml

   Does anybody know anything about this Singaporean initiative? https://ifc2citygml.github.io/

9. R by ReD_CoDE on 21 Oct 2020 #

   @Moult said:

   Does anybody know anything about this Singaporean initiative? https://ifc2citygml.github.io/

   I aware of that, but is less interesting to me, because of its low LOD approach, LOD 0, LOD 1, and LOD 2

   You can achieve low levels by some mapping/parsing techniques which are good in some scenarios

   Also, there're other considerations about CityGML and IFC, especially IFC

10. S by shanmama on 23 Oct 2020 #

    @aothms said:

    I agree, @ReD_CoDE, with my university I'm working on exactly this. We should be able to release something rather soon under an open source license. It'll be based on a version of IfcOpenShell that uses CGAL in addition to OCCT, https://github.com/tudelft3d/IfcOpenShell/tree/cgal/ which was a monster effort, but is getting near to something usable.

    I have been using your IfcOpenShell-Python. To a certain extent, he helped my research. Thank you very much

11. S by shanmama on 23 Oct 2020 #

    @Moult said:

    For the record I think the repo for conversion is here, but it seems a little old :) https://github.com/tudelft3d/ifc2citygml

    Does anybody know anything about this Singaporean initiative? https://ifc2citygml.github.io/

    This Singapore research seems to be just an introduction, I don't know their products or codes.

12. L by LaurensJN on 23 Oct 2020, edited 23 Oct 2020 #

    It is not an OS solution, but FME has some conversion tools between IFC and CityGML. They provide some free trial license, so you could try to use it for a reference :) It takes some time to learn though..

    Here is what they do for LOD3:

    https://community.safe.com/s/article/bim-to-gis-advanced-ifc-lod-200-to-lod-3-citygml

    edit: I have not tried to do a conversion between IFC and CityGML with FME, I just know it exists

13. A by aothms on 24 Oct 2020 #

    The approach from Singapore NUS is a graph rewriting approach. Conceptually quite pure, but I expect it'll require exceptionally well modelled buildings and really good exporters to have proper output. Last time I checked FME it was just piping building elements independently through their feature conversion pipeline so you also don't get a valid facade shell. Our approach in Delft is a lot of geometrical processing to glue everything together and eliminate invisible surfaces, but in the end it'll likely give a more robust solution.

14. R by ReD_CoDE on 24 Oct 2020 #

    Esri has a coherent article about GIS+BIM:

    https://www.esri.com/arcgis-blog/products/arcgis-pro/transportation/common-patterns-for-bim-and-gis-integration

    just they didn't aware of a new approach at that time, which I shared with them:

    https://databricks.com/blog/2020/01/30/what-is-a-data-lakehouse.html

    However, as mentioned before and even two coherent articles from TU Delft which Thomas is part of that team mentions, the important part is about geometry/topology

15. M by Moult on 24 Oct 2020 #

    @LaurensJN I recently tried out FME's conversion tools, and discovered they don't support geolocation in IFC ... the good news is that in FME you can script your own little property extractor so you can work around it somewhat by storing geolocation in another unofficial property, but... :)

16. B by bernd on 25 Oct 2020, edited 25 Oct 2020 #

    In case of the Singapore stuff. It is not open source AFAIK. I know one of the members according website from Singapore is on FreeCAD forum too. I will give a hint to this here.

    Cheers bernd

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