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I'm having problems importing a public source file containing 3D buildings in The Netherlands into our 3D BIM software ArchiCAD. The website (https://3dbag.nl/en/viewer) offers 3 types of files, including OBJ-files. The proposed workaround is to import the OBJ-file into Blender and export a Collada file for use in ArchiCAD. However, when I open the Collada (.dae) file in ArchiCAD the geometry is all messed up and doesn't look like the preview in the website's viewer anymore. Is there a way to import the OBJ-file into Blender and retain the exact geometry that should be in the file?

Another method we have tried is using the CityJSON-file and importing/exporting through QGIS, but that resulted in a non-solid wireframe. This wireframe did have the correct geometry though...

Another method was using a plugin called Modelport which imports OBJ-files directly into ArchiCAD. This works, using the same OBJ-file, and gives the correct geometry. However, this plugin is not open source and costs quiete a bit.

The above trials show that the correct and accurate geometry IS included in the OBJ-file but somehow gets distorted while importing into Blender. I know the software is called Blender but I would expect it to be possible to import a 3D file 'unblended'.

If anyone has any idea how to fix this it would be very much appreciated!

The file I'm currently looking for is this one: https://3dbag.nl/en/download?tid=1024

Below are screenshots of the 3D buildings in the online viewer on the left, and the final 3D model imported into ArchiCAD (through Blender) on the right.

3D BAG viewer (left) and ArchiCAD (right)

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This is a floating point precision problem. Then you import objects in Blender, do the following (imported objects should be selected):

  1. reset object centers by pressing Object → Set Origin → Origin to Geometry

  2. reset position:

Look at transforms:

enter image description here

Press G, then X and subtract the X position by pressing the same number:

enter image description here

Do the same for Z axis. If you do everything right, objects will appear on the screen:

enter image description here

Objects, that are close to scene origin, are more likely to have less precision problems. Proceed with export.

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  • $\begingroup$ YES! Thank you for this, this works! Now I'll try to clean up the triangulation some more and try to find a way to ungroup this model so I can export a selection to ArchiCAD. $\endgroup$
    – Thomas
    Commented Oct 11, 2022 at 9:24

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