Pagina's op IkLeerBIM

vrijdag 24 februari 2017

A tool to build Revit's IFC mapping tables - feedback and revision




Based on some questions I received lately I would like to explain some things about the spreadsheet.


First of all I did update the excel spreadsheet recently to fix a translation bug in the formula (Ctrl H . the Dutch CEL("inhoud" for CEL("contents" in the whole model 6131found) It works as good as it needs to be for now. And the waiting is still on Autodesk to really change the way to interact with IFC. The spreadsheet is nice for a + user. But most people can do their job real nice without it.

The spreadsheet consist of 4 sheets (in green) for making an import, export and parameter mapping table. The 4th green sheet is the one I like the most, because I learnt the most about IFC with that sheet. All the other sheets are mostly used for reference. The first 3 green sheets have a grey part. This is the actual mapping text. You should select the cells that you need, copy those to clipboard and paste them in a new .txt file. Or simply change an existing table. The grey part will change if you change orange cells beside it. The formula in the grey cell will report and look first at the column with >>1 (in Row 1), and then to the column with >>2 and so on. It’s like a filter. The first rows will contain some + options. Just read and try, or simply leave it as is – it’s not that important.

The spreadsheet links .txt files while opening the file. You should check that all the files are (re)loaded by excel correctly.  Later you can change every file differently if you want to. Just check the Data Tab \ Connections group \ Connections.
Most of the .txt files will appear in the ‘reference’ sheets I mentioned earlier. If you are not familiar with data connections in Excel, just google a bit. I found some English explanations here. tutorialspoint.com - External Data Connection
When actively using this spreadsheet with different projects, you can change the export.txt, import.txt with every new project. Or reload these connections with new project specific .txt files. You can make those .txt files in Revit in the IFC option menu – Save As.. Exporting from a project will make sure that you got every subcategory covered.

You can later on also change the standard DRS / standard AIA settings for your own standards. You can do this if you feel more comfortable with the spreadsheet. By doing so you will able make your own referencing standard.


Then the most important part...


Fill in Revit Export 
This export table suggest that you can actually map every single revit subcategory to a different IFC entity. But it mostly works as an do or don’t export table in Revit. Using the IFCExport parameter is still necessary.

Fill in Revit Import
Is nice, but importing an IFC works already fine, by just linking everything and use Revit’s native settings. If you want to do more with the import part, you should also look into this guy.
http://geometrygym.blogspot.nl/ and
Ifc Import Class Category Mapping

Fill in ParameterMapping
Is nice for a + user who wants to know all the options that native IFC has to offer, and wants to use it. But there are also other ways to add parameters to an IFC entity and they also work fine.
If you want to map IFC common properties to your own / specific Revit Shared Parameters. Override or change the link for the file RevitGG_IFC Shared Parameters_20121102.txt to your own Shared Parameter File. This will be loaded in 1 of the last Sheets called “Shared Param DRS”. The whole Column C in that Sheet is an Excel Named Range with the Name “Shared_Param_DRS”. This will be the content of the drop down menu in the Sheet “Fill in ParameterMapping”, Column M so you can use it.
With the Sheet “Fill in ParameterMapping” you need to copy only parts of the grey cells that you really want to map. Skip in the .txt editor the PropertySets or Properties that you don’t want to use. Check the Data Type of the properties to make sure it will work. I didn’t build a check for that. And everything will be “Text” at the moment. Some Properties are hardcoded in the IFC exporter. So if it doesn’t work as expected, do ask on the Sourceforge side. This is not all documented at the moment. There is something more info over here:
Mapping of Revit parameters to IFC values 
Custom parameter mapping
Revit IFC Support for Extended FMHandOverView Definition (used for COBie)

IFStructure 
I like this one a lot. It gave me a lot of inside in the IFC structure / missing entities / new types / new parameters that I didn’t know off. And the direct link to the building smart site is very convenient. Because of the last 3 remarks I did stop working on this spreadsheet. And It’s good enough for now. I did had 1 request to add the IFC layers but didn’t build it. And don’t know if I will add it in the future. What I did do, is follow the conversation on the Sourceforge site. And I will add a few links. Perhaps these conversations with Autodesk will clearify some IFC related question that you also have, just as it did for me.
Inherited propety sets
IFC export mapping table

Have fun with this spreadsheet. Hope it helps a little, to tweak IFC and Revit.
Or that it at least will give more clarity on IFC.

Kind regards,
Teun de Vries.

Also thanks to Rene Pellicer Garcia for your feedback.