Ceilings, IFC and Revit

[kevin b]

How are others exchanging IFC files with Revit users and getting ceilings to work? And telling them to stop using Revit is not really an option.

In this case we are talking about ACT ceilings. we model our ceilings as slabs with a material assigned to them for the 2x2 or 2x4 grid, the material has a vectorial fill assigned to it, and we use the fill of the surface material as the fill in plan so it showss up nice in model and in RCPs. When we export this to IFC for use in Revit by MEP engineers, no grid. In fact Revit reads the ceiling slabs as floors. This is seemingly a Revit problem (which some would argue is really an ArchiCAD problem ie why are you making ceilings out of slabs) but considering the numbers of Revit users I need a way to play nice with them. What are others doing?

I have the IFC reference guide and its great that everything tells me I can change or add parameters but have no idea where in the hundreds of potential parameters that are already there, I'd even begin with.

Along similar lines how do I get the materials applied to said slabs to export in IFC. The only thing I can find for now is that I need to make a new cut fill for ACT as it seems like the cut fill information is beign associated with the exported slab object. While that would fix one issue it doesn't get the engineers a grid they can work off of.

[owen]

Kevin,

Just stumbled across your unanswered post - I realize its almost a year later but will answer anyway:

1. Ceiling 'Slabs' in Revit - with ArchiCAD 14 you can now specify the IFC Element type directly in the tools 'Listing and Labeling>Classification' tab. Revit should no longer think the slabs are slabs. I have argued for a while that ArchiCAD needs to take such an approach for internal modelling whereby you can use a series of more generic element modellers and then tell ArchiCAD (and downstream applications via Export) what those elements actually are (Walls, Slabs, etc). This would get around the constant limitations in element-type specific tools ... such as when you use a Mesh to model a Slab. Anyway, enough of that ..

2. Materials via IFC to Revit - Still doesn't happen unfortunately. There is no support AFAIK in IFC for 2D element types like hatching - which is what you have applied to your ceiling to create the grid. There is also still no way to export a proper Grid (Structural or Ceiling) from ArchiCAD via IFC

(This last point is what brought me to this post - trying to set up a 3D Grid for sharing with consultants / sub-contractors mainly using Revit)

cheers,

owen

[Da3dalus]

We've got to keep this topic running... there also a wishlist thread for a whole new Ceiling tool Here. I'm working with some people in my office to find the best way to convert. Up until now, we have had to use a grid of beams, typically using the model view in the ceiling plan to only show the centerlines. However, not only is that a slow painful process to draw those beams, but what do you do if you're trying to show real exposed beams with thickness in your ceiling plan?!

I am working on a file to try out different methods to compare in IFC/Revit:
1. The beam method described above;
2. Using the Curtain Wall tool horizontally (difficult to edit);
3. Using slabs or roofs with boolean beam cutouts;
4. Using a Ceiling Grid Slab Accessory (not sure where it came from);
5. Using ManuBIM Ceiling Editor v2 from BIM-Components (haven't tried yet);
6. Using slabs and play with material settings.

I will compare the difficulty in editing against the quality of Revit results and let you all know. If anyone has more ideas, bring them on!

[kevin b]

We have found the best results using the Ceiling Grid Slab Accessory. We found you need to have lines on on both sides option for it to work as intended to get the grid centerline to the Revit guys. The only downside is remembering that the accessory is there because now you have two grids, one for materials and one in the accessory so you need to keep them consistent.

The curtain wall tool seemed to be OK but even though we could make it look right in RCP and model you had to export it with the actual physical grid width which did not give consultants a centerline of grid to snap to. Even if it was set to the show centerline option.

The cut out of grid would seem to have similar problems (ie. no centerline for Revit)

Materials don't seem to cut it, at least not yet.

[Da3dalus]

And another solution has been brought to my attention, an Interior Wizard Accessory out of the UK for ceilings which looks promising. I'll see if I can purchase it. An explanatory video is here. The Suspended Ceiling Accessory by Applecore is £60 (about $90 US), and appears to be very versatile. Nonetheless, I'd love to see ArchiCAD provide a native solution.

[Laszlo Nagy]

Are you guys aware that there is a free Ceiling Object available from BIMComponents.com that offers such functionality:

http://archicad-talk.graphisoft.com/viewtopic.php?p=208515&highlight=#208515

[tsturm]

Has anyone figured out the correct mapping to get slabs used for ceilings to be be Ceilings in Revit?

Coverings brings them in as Generic. Slabs brings them in as Floors.

[Laszlo Nagy]

So, if I understand this correctly, Archicad needs to correctly classify elements as "Ceilings", and the proper "IFC Types Mapping for Export" settings need to be used. "Ceilings" need to be converted to the "IfcCovering" IFC Type, and its "CEILING" Predefined Type. If you use the "Revit Export for Reference Model" IFC Translator, these are the settings that will be used for elements classified as Ceilings:


As far as importing into Revit, check Page 18 of the following PDF:

https://damassets.autodesk.net/content/dam/autodesk/draftr/2528/180213_IFC_Handbuch.pdf

There, it talks about the Import IFC Options Dialog.
Check that for the "IfcCovering" IFC Class Name / "CEILING" IFC Type combination, the specified Revit Category is "Ceiling".
Then I think it should go through correctly.
Unfortunately, this is in theory, since I do not have Revit and I cannot test it.