[BlenderBIM] Deleted objects still exported to IFC

edited June 25 in General

I have made a very simple IfcProject in BlenderBIM, with three IfcBuildingStoreys and an IfcBuildingElementProxy to clarify where the 0-point is in IFC viewers.

I have imported a precast concrete slab from a supplier, I opened a new Blender session, copy pasted the geometry and set the IfcClass I wanted. I was playing with Copy Paste and Duplicate. And exported it to IFC.

However after I was done, I wanted to delete the slabs again. But when I make a new IfcExport the slabs are not deleted. Am I missing something I need to do in Blender? I know it's still alpha software. But is there a workaround? Sometimes I am seem to be able to delete and add objects without a problem. I have no idea what's going on.

BlenderBIM is absolutely amazing by the way :-). Can't wait to see it mature


  • You seem to have some overlapping slabs in your model, so if you delete one, you might see the one underneath. Deletion seems to work here, but there may still be a hidden bug somewhere, as you say "sometimes you seem to be able". However, without being able to replicate, unfortunately, I cannot fix it nor confirm that there is actually a bug.

  • Same trouble here.. importing a 45MB 'revit' ifc in Blender 2.93.1. I select and remove Blender objects, that are also BIM obejcts.
    Delete the ifc-filename, and export to a new file.ifc (which is very much faster (minutes) than to save over the file-input name..this takes hours)
    Reopen the newly created ifc..and the items are still there? selecting the object, does not tell you where in the collection that object is..just to try to delete from the collection (in case it makes a difference?). I should go with much smaller files to find out..
    Next is to move the whole ifc 30cm in Z direction.. since at the merging of 2 ifc's, i found out they were shifted to each other.. there is no georefernces. Anyway, starting to be fun using BlenderBIM and usefull..

  • @lukas when you delete an object, it will only truly delete it upon the file export process. If you delete the IFC-filename, it may refresh the object cache and cause the object deletion not to succeed. I will take a closer look. I have been slowly fixing bugs in the sync progress so perhaps this might've already been fixed.

    As for shifting everything, use the IfcPatch recipe for OffsetObjectPlacements prior to merging the IFCs. The arguments it expects are [x,y,z,a], where xyz are numbers for a translation, and a is an angle in degrees.

  • edited July 2021

    Thanks @moult. I will give it another try without changing the project name. But how comes that the export is then sooo much longer?
    Does it help saving the blend-file after deletion. then reopen this blend-file, and then export to a new ifc? (so bypass the cache reactivation?)
    no this doesn't work out. reopening the blend-file does make an ifc out of it..complaining that there is no ifc in memory to be exported, make sense.
    Shifting works perfectly.. Deleting works best when one moves the selected items to a new collection, and then remove that collection..
    No I can modify IFCs (delete and/or shift) and add (merge) other IFCs to new IFC. Great.. my boss is impressed :-)

  • Moving ifc-objects within Blender and exporting the ifc (to the same file) works fine. But I do again have problems with removing IFC-objects from the ifc file.. (it disappears in Blender, but keeps being present in the exported ifc). This procedure with a another collection doesn#t help no more.
    new versions, new behaviours? how to remove an unwanted ifc-object and save the result?

  • edited March 19

    @lukas good question. I get this behavior every so often, as well.
    I haven't nailed down a definitive cause/effect, but I'm thinking it might have something to do with undoing and redoing operations. Could be wrong.

    To fix, are you able to import in the IFC and start from there to make a new Blender file, or would that be too destructive, that is, loosing too many modifiers and collection instances, etc?

  • edited March 15

    In the scene options of Blender, for the 'IFC Project Info', there is an export function as 'IFC MVD'. here one can rename (re-export) the ifc-file.(icon in the middle)
    The way with saving a *.blend file, reopen it and assign a new ifc seem to work too.

  • edited March 15

    Some CAD tools still are on 2x3 !! so can we drowngrade from ifc4 to ifc2x3 ?
    is that a IFC-patch recipe? got it.. https://community.osarch.org/discussion/902/

  • edited March 15

    what are migrate arguments?
    input ifc: filepath/name in IFC4
    output ifc: fliepath/name in ifc 2x3
    Arguments: '4 to 2x3 ' or 'downgrade' or ??

  • Hi, Im still seeing the same non-deletion issue on a small test projct im working on. No matter what I try (unlink , delete, re-export, new belnder file, import ifc) the ifc elements remain within the file. Only methods to permamnently delete is to open the ifc in text edit and delete the guid reference and re-save the text file. From the above it sounds like this issue has been resolved for most?

  • edited June 17

    Can you share the IFC file (or a pared-down version of it) and show us what object you're trying to delete? We can try to replicate on this side, as well.
    Also, start blender. Then do this..

    And then import your IFC. Then try and delete object then do this...

  • Hi theoryshaw, thanks for the advice, no joy with the above though. .ifc attached. Pretty basic but you'll see quite a few duplicated rogue elements which I can't remove (glazing, mullions, burners etc.).

  • Thats odd. I'll try on my windows machine, currently using OSX. Assume you were just deleing the object, not un-linking and then deleting?

  • Working as expected on Windows, just getting a few errors when re-saving the .ifc from the .blend file which I'll dig into a bit later...

Sign In or Register to comment.