IFC import geometry unwieldy

[Matthew Johnson]

When importing IFC (from Revit Structure) beams and columns generated from BREP (ie more complex than a flat extrusion) the geometry created either in Morph or Object format is of such a high polygon count that navigating the resultant model is impossible.

Does anyone know of a method to reduce the level of detail in the imported objects and profiles so that the intent (eg steel I beam) is maintained without the massive polygon count being generated?

Would also be useful to know of any methods for rationalising Morphs created from imported objects.

[Laszlo Nagy]

Are you using the Graphisoft IFC Revit Add-In when exporting from Revit? Does that make any difference?:

http://www.graphisoft.com/downloads/interoperability.html

[Matthew Johnson]

We have tried both with and without the plugin. Grids etc work better with the plugin but the issue of geometry detail is still there.

[Laszlo Nagy]

Then you should report this issue with files to your local reseller for further investigation.

The Morph Tool has some commands for smoothing edges and faces but that may not give the result you are after. Other than that you can always select any unneeded edge and delete it (for example, if a planar surface is unnecessarily triangulated), but that may be drudgery if there are many such elements.

Please also note what I wrote in response to another IFC-related question, it may apply to your case as well:

http://archicad-talk.graphisoft.com/viewtopic.php?p=215277#215277

[Matthew Johnson]

Thanks Laszlo,

We are already doing a version of that because of difficulty in getting the coordinate system coming out of the Revit IFCs.

Unfortunately the clean file that we are putting the Revit IFC into is barely navigable on its own and I'm too afraid to see what it does speed wise once I module it into our Teamwork project.

To give you an idea of the sizes we are talking about.
Teamwork file saved to a solo file as is = 140Mb
Solo file once all Sections, Elevations, Details and Layouts removed (ie model data only) = 5Mb
Clean ArchiCAD file with only the Revit IFC imported (no 2D data etc.) = 21Mb

If the structural model data alone is 4x the size of our architectural data we are going to have to start taking a lot of long coffee breaks while we wait for the sections to rebuild. (haven't had to do that since V11)

[Matthew Johnson]

I don't mind so much that the more complex elements such as 20Ø rod cross braces come is as objects but when one I beam that is flat is recognised as a beam with a cross sections profile etc. and the one next to it is inclined at 3° and all of a sudden becomes a complex morph or library part with 1000's of triangulated faces.

In discussions with our engineer we think it has something to do with the angle the end of the member is cut at.

- In ArchiCAD a beam end is always vertical (unless you start doing SOE to it)
- In Revit a beam end is always perpendicular to the beam's axis and needs to be modified to give a vertical end if that is what the design requires.

It seems too much of an imposition to ask the engineer to design the beam ends in the project just to suit the limitations of IFC.

[Matthew Johnson]

Just to clarify I've done the following snapshots of the same model in Solibri and ArchiCAD.

[Matthew Johnson]

And to give you an idea of the level of detail the morph bodies have.

No that's not a black material; that's the number of faces blurring to infinity. And at only half way through design development we already have over 1000 of these.

[Anonymous]

Any chance to post a single problematic beam as a revit file and resulting IFC file?

[Laszlo Nagy]

Does the exported IFC have a very high polygon count also in Solibri or only in ArchiCAD?
If the IFC already has a high polygon count than it has something to do with how it is exported from Revit.
If it has high polygon count only in ArchiCAD, then the ArchiCAD import of IFC is the culprit.