TEETHING PROBLEMS – GC to Revit – My response

QUESTION FROM READER: I’ve integrated the GC tool (thanks to the Revit conference contacts!) into an elective class starting early next year and am working with some Masters students using this and Rhino’s Grasshopper tool.
There are still teething problems with the integration back to Revit (or into a BIM workflow is more accurate I guess) and would appreciate and comments on this.


Hi David

I will just quickly respond to your question – in brief – and say the following:

I am okay with the GC model remaining in DWG format with the Revit model. (I know this is technically not best practice – but I think in this instance the pros out way the cons. I would say in response to your question that I am also okay with GC generating all the required BIM data for the GC part of the model. whilst the Revit model generates the data for all Revit related model.

In that sense I do think that we need to reconsider the purist approach/ ideal that so many have clung to for so long…

The more I get to grips with BIM the more I believe that BIM should not be so much a single model driven solution as much as it should be a database- associated-with-a-collaborative- collection-of-models-solution.  (Ha-ha … A new term for scrabble fans ;-p)

My point being that the ideal of cramming every single bit of information into a single model environment (even per discipline) might – potentially- be too idealistic given the current limitations within software’s from various sources to integrate fully.

I hope this answers your questions in some form.

  • Essentially my approach would be to build a Revit model where appropriate
  • Import a GC model (in DWG) where Revit cannot generate the require form and complexity
  • Generate automatic Fabrication plans (AMEN!!!!!) through GC and import into Revit to keep documentation output set tidy. (This will become an ongoing management task – since the GC will not remain live if changes are made. But I think it can be managed with good ol’ fashioned communication ;-)
  • Schedules for Revit model obviously come from Revit
  • Schedules for GC model from GC- Since the GC form could not be generated in Revit (And if it could you would obviously do it in Revit – unless GC fabrication plans where still a requirement) So in that case import schedules into Revit or even better… export all relevant data into a neutral database environment.

That would be my plan of attack… which I’m sure might ruffle a few feathers – but hey there’s always more than one way to achieve an out come.

I hope that was helpful and has answered your question for the most part.

I would just say that I would not waste hours of my life converting a GC model into Revit massing (Apply by face) unless it was really-really worth while. And I can’t imagine when it would be…mmmm… Sure it means you will need to dimension the GC model every time you re-load but my response to that would be – dimension the GC model in detail only when it’s resolved!

GC is a very specific software that should be used to generative a unique range of forms that currently Revit and other 3d modeling software’s currently cannot.  Sure – there is some time lost in rework of dimensions… but hey – I wouldn’t be game to try model some of the GC forms in Revit. Apart from the fact that you must remember that the BUZZ about GC is it’s ASSOCIATIVE, LIVE and can generate new forms based on new formulas or constraints. Use it’s strengths and adapt your BIM solution accordingly. That would be my approach.

I’d be happy to approve your comments and findings if you wish to share them on this blog in future. Mm… I did say it was going to be a short response – I cant seem to help myself sometimes!!! Have fun.

Cheers for now




Great Generative Component links – Explore some more

To All

I am adding this reply as a seperate post as my blog tends to hide replies in a logical place (below original comment ;-p) ….. but some of these useful links may not show up instantly to a new reader – so forgive any duplication.

Hi David

I’m glad to read that you are exploring GC!

To be honest I’m a bit snowed under right now to add much more on the Revit and GC challenges and benefits. Testing and learning more about GC has gone on the back burner for a while since I am working on an international project that was nominated at the RTC this year.

As you would know I am part of the committee that is working towards trying to define some best practices & standards/ guidelines for Revit content across Australia and New Zealand.  The project is proving to be a bit of a beast but we are making some progress ;-)

Fergus or Sean (from Bentley) have offered to be of assistance to anyone wanting to explore GC in more detail. Here are some links they sent me a few days ago that I hope may prove useful to curious GC fans….

You are most welcome to add any finding of your testing to this blog as I’m sure other readers would be excited to hear what you discover along the way. I have also invited Sean to comment to any of your responses on my blog should they pop up.

The video from the RTC GC demo is now up on the Bentley website at http://www.bentley.com/en-AU/Promo/ANZBIM/


The direct link to the GC demo video stream (which we covered at RTC in my talk segment this year) is:


To contact Fergus or Sean please email Fergus at Fergus.Dunn@bentley.com and he will direct emails accordingly.

Best of luck and please let us know how it all goes!


Again I would like to thank a team of people who also assisted me along the way with being able to present Generative Components this year in my talk.

 Stephen Taskin – Associate    [Altis Architecture]

Many of us have known Stephen for years in the Revit world. He has spoken on advanced Revit Modeling several times before at RTC. As always Stephen loves pushing the boundaries of what’s possible so of course it was not hard to get him to join me in this exploration. Thanks Stephen – I know you have been so busy!

  •  Fergus Dunn – Building Industry Director – Aus/NZ
  • Sean Dodsworth – Building Consultant –

[Both from Bentley Systems]

 I would also like to give a special thanks to Sean and Fergus. They have gone out of their way to make sure our Revit audience will get value from the GC demo at RTC in a context that does not detract from Revit in any way.

How GC models behave inside Revit files

How GC models behave inside Revit files

A special thanks to Lars Moth-Poulsen who is an Application Engineer at Bentley Systems, who did a great job in building the demonstration model and who is also a great teacher of GC concepts ;-)




  •  Massing cannot be applied to surfaces
  • But there seems no need to be able to do that
  • Cuts in all views
  • Can dimension. Aligned dimensions work best – since twist can cause elements to no longer be parallel to screen work plane. Arcs can be dimensioned if cut, like Revit. Create point as work around.
  • Better when updated, since massing is not reformed.
  • Obviously changes made on reload will mean dimensions are lost. Small price to pay for flexibility and re-generation speed of form
  • Fabrication plans can be imported into Revit
  • Fabrication readings of x,y and z co-ordinates can be reported in schedule format through GC.
  • Layers can be switched off in VG to create various set-out drawings – like structural versus glazing etc.

 GC Export

Here are some tips of best settings from Sean Dodsworth (Bentley Solutions) when saving the GC model into a DWG format that is best for Revit®

GENERATIVE COMPONENTS – How to import into Revit

When doing some testing about how to best bring a GC model (3D-DWG format) into a Revit file we came to the following colcusions:

Essentially we had two option:


  •  It is treated as one complete object. Elements cannot be selected individually
  • No massing can be applied
  • Less control when trying to dimension to it.


 Loaded into Project file

  • Makes reloading easier and accurate since origin point and offsets are already defined. Bring dwg in the same place in family. Then okay.
  • Can apply massing to the elements, but it can be a bit tricky due to the complex nature of some forms.
  • When form is changed, the massing in Revit disassociates since the reference in no longer the same. (Linking not an option in Revit family files) Massing elements can be re-associated to dwg.
  • Updates will drop dimension
  • Layers can be switched off in VG to create various set-out drawings – like structural versus glazing etc.


I wanted to introduce a software solution that creates some impressive massing forms that go beyond parametric design and move into associative relationships.

Generative Components - Conference Pilot

  • It offers unique forms that are based on formulas and point driven relationships. Building associated relationships that literally dictate the form. By changing an association the form quickly morphs into a new shape.
  • I am not introducing this software to propose we ditch Revit – obviously – but it is potentially a useful tool – just like Sketch up, Inventor or Rhino.
  • I see it could be used for an architectural feature, like an awning, sculpture, sky light or even part of the building form.
  • It can be brought into Revit. We have done some testing and I will include our findings in the next few posts.