Deleted objects in Blender still exported to IFC

edited July 7 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 22

    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 :-)

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