Error report IFC

[langk]

I recently modelled a simple house in FreeCAD and exported it to IFC4. Then I checked the IFC file for errors. For the general improvement of the IFC export from FreeCAD, I list the found errors below.
I have taken the information on the causes of the errors from the current bSI IFC specification.
The errors are always formal propositions that have not been adhered to.

• 1. IfcAxis2Placement2D.LocationIs2D and IfcAxis2Placement2D.RefDirIs2D
  IfcAxis2Placement provides position and orientation to place objects in a two-dimensional space. LocationIs2D and RefDirIs2D require a dimensionality 2.
  
  In my model both errors only occur with walls. The modelling of the affected walls does not differ. Lines were drawn and the wall tool were used. Walls of every level in the house are affected, some have doors, others don't.
  
  Both errors occur with IfcRectangleProfilDef.
  
  Here is an excerpt of the IFC:

  

  ifcaxis.PNG (26.91 KiB) Viewed 1861 times

  As you can see, IfcRectangleProfilDef refers to IfcAxis2Placement2D. 2D because IfcRectanglePRofilDef is given by X and Y only. IfcAxis2Placement in turn refers to #2594 and #2593, both with 3D coordinates. And that's where the mistake comes from. 2D is required, but 3D is given.

• 2. IfcGeometricRepresentaionContext.North2D
  
  North2D requires that if TrueNorth is specified, it must have dimensionality 2. As can be seen in the lower IFC section, this is not the case. Instead of 2D, 3D is given.
  

  

  TrueNorth.png (8.21 KiB) Viewed 1861 times

• 3. IfcGridAxis.WR1
  
  This error affects all my 4 fixed axes. The reason for it: also here a wrong dimensionality is indicated. WR1 requires a dimensionality of 2. (see IfcCartesianPoint)
  

  

  axis.PNG (26.89 KiB) Viewed 1861 times

The errors mentioned in No. 1,2 and 3 can easily be corrected by deleting the last coordinate. However, it should probably not be the usual approach.

• 4. IfcOwnerHistory.CorrectChangeAction
  
  CorrectChangeAction means: if ChangeAction is enabled and LastModifiedDate is not defined, ChangeAction must be set to NotDefinied.
  But all objects get the change status .ADDED. which, in conjuction with the error, suggests that LastModifiedDate does not define. This would have to be corrected in the implementation.

  

  ownerhistory.png (4.82 KiB) Viewed 1861 times

• 5. IfcRelConteainedInSpatialStructure.WR31 and IfcSpatialStructureElement.WR41
  
  These two erros affect the same element: space.
  The spaces are currently connected to the floors via the relation type IfcContainedInSpatialStructure. But according to the specification this is wrong. A spatial structural element (which a space is) may not be connected to another spatial structural element (e.g. floors) via IfcContainedInSpatialStructure. IfcRelAggregate is required for this purpose.
  Only components should use IfcContainedInSpatialStructure.

• 6. Invalid 4-byte Unicode character
  
  This error refers to an adress that I entered into the site, especially to some letters that do not occur in Englisch.

Just for information my used FreeCAD version:
OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.18733 (Git)
Build type: Release
Branch: master
Hash: 2637280c1d2cb48e7cd946fa9f2484467edd8b0c
Python version: 3.6.7
Qt version: 5.12.1
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)

[hlg]

I can confirm these errors and will created a pull request to fix 1-5: https://github.com/FreeCAD/FreeCAD/pull/2766.

I am not sure about 6. I think I have seen some discussion around IFC UTF8 encoding issues before and I know it is a bit peculiar. Maybe someone more familiar with it can have a look?

[bernd]

damn IFC and utf8 ... and the move from Py2 to Py3 makes it even more a challange.

Would you post a simple example?

Have you tried 0.19 dev version.

[hlg]

I think 0.19.18733 is the latest dev version, no?

[bernd]

I think 0.19.18733 is the latest dev version, no?

upps my misstake, I just saw 18 but it is 0.19 allready ... Nevermind guys ...

But an simple example would still be cool.

[yorik]

This is indeed a defect in FreeCAD. We export almost all position vectors as 3D (3 coords). This works as there isn't apparently something in the schema that prevents it, and haven't seen any BIM app to have problems with that yet. But it's not correct indeed...

As for encoding, that too is annoying. IFC uses a very boring encoding. Normally, IfcOpenShell takes and gives utf8 and does itself all the conversion work. There might be some bug there too... Would be interesting to narrow down to exactly what works and what doesn't

[langk]

Here is the street name i used: Kačićeva ul. 23 - It's a street in Zagreb, Croatia.
And here is the adress in IFC.

adressZagreb.PNG (4.46 KiB) Viewed 1746 times

As you can see the letters č and ć are not readable. I also tested the Croatian letters dž, đ, š, ž and the German Ä, Ü, Ö. Not only they are not readable, they also result in an error while checking (invalid 4-byte unicode character).

[bernd]

I swear this has been woriking ... I have spent on this hours over the years ...

Realoading the ifc in FreeCAD but BIMCollabZoom does not read the file ...

Value in FreeCAD:
Funny character dž, đ, š, ž, Ä, Ü, Ö street

export FreeCAD:

Code: Select all

#24=IFCPOSTALADDRESS(.SITE.,'Site Address','',$,('Funny character d\X4\0000017E\X0\, \X4\00000111\X0\, \X4\00000161\X0\, \X4\0000017E\X0\, \X4\000000C4\X0\, \X4\000000DC\X0\, \X4\000000D6\X0\ street'),$,$,$,$,$);

character_project.ifc

(4.62 KiB) Downloaded 64 times

character_project.FCStd

(19.45 KiB) Downloaded 58 times

BIMCollabZoom:

screen.png (6.38 KiB) Viewed 1731 times

[bernd]

Attached the way Nemetschek Allplan does export this line ...

Code: Select all

#53= IFCPROPERTYSINGLEVALUE('Bauvorhaben Adresse',$,IFCTEXT('Funny character d\X2\017E\X0\, \X2\0111\X0\, \X2\0161\X0\, \X2\017E\X0\, \X2\00C4\X0\, \X2\00DC\X0\, \X2\00D6\X0\ street'),$);

BIMCollabZoom:

screen.png (11.74 KiB) Viewed 1732 times

[bernd]

https://forum.freecadweb.org/viewtopic. ... =30#p96368 ... back in 2015 ...