Linking IFC/RVT files into projects with Project North differing from True North

[Haider_of_Sweden]

I am trying to understand whether it is a question of Revit logic, ie "what revit wants you to do" and in that case, that I have misunderstood the Revit logic, or if it is in fact a bug.

Site.RVT - this is the site model, with Project Base Point on its right position (not at 0,0,0). The site model has also a project north, oriented nicely to the building's orientation.

Model.RVT - this is a model where True and Project north are pointing the same way - perpendicular to the building, ie not how the building is actually rotated in the real world.

Model.IFC - this is a model I received from an external part. This model is oriented correctly to real world.

When I link the IFC file to site.rvt that has a project north defined (different from true north), I am counting that the model will be oriented to true north. I am assuming that Revit will prioritise True North before Project North.

What is happening though, is that the model is oriented as if Project North is True, and hence, in true north, it has an offset rotation.

I could, but I don't want to manually rotate it to its correct rotation around Project Base Point as rotation axis.

Instead, the solution I have is to reset Project North (so it matches True North), do the linking, and once I am done, I recreate Project North.

In my opinion, this method cumbersome, not to mention that it actually causes some troubles for me (things disappear in the project).

When I import a RVT-file, I can understand that the same behaviour would occur, because True and Project North are the same and whether Revit favours True or Project north, the result would be the same. To prevent this, I need a Shared Coordinate System, this I understand.

But why is this happening when I link IFC files where the models are oriented correctly to the real world.

Does Revit favour Project North before True North?

[H.echeva]

Hello,

From my experience and as far as I know, IFC files don't have shared coordinates. 

What I have done in the past is to insert the IFC to a separate empty Revit file using origin to origin (if the model is oriented properly the internal origin will probably be fine). then you can put a marker with Model lines in the Revit Internal origin. When you import that revit file into the Site, use the markers to align it with your survey point.

I know it might not be very clear, but you can play with the idea.

Regards

[Haider_of_Sweden]

Hi!

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@H.echeva wrote:

From my experience and as far as I know, IFC files don't have shared coordinates. 

Shared coordinates have never been the issue. I link to Project Base Point and it works perfect. Only problem is the orientation.

I feel it is strange that Revit favours Project North before True North when linking IFC. One should assume the IFC comes in True North orientation and therefore oriented to True North when linking. This is not the case.

So I need to make sure if there is an official statement about that, ie that this is the (weird) way it should be.

Otherwise it is a bug and then I would need to report it.

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@H.echeva wrote:

What I have done in the past is to insert the IFC to a separate empty Revit file using origin to origin (if the model is oriented properly the internal origin will probably be fine). then you can put a marker with Model lines in the Revit Internal origin. When you import that revit file into the Site, use the markers to align it with your survey point.

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Yes, this is what I do in the meanwhile - a RVT file for just IFC files. This one shares coordinates with the main project file.

However, I do not like marker objects because I fear there might occur unit-errors or such. Shared Coordinates or linking to Project Base Point is what I prefer.

[KIMRAMFI]

Hi @Haider_of_Sweden 

I will try to explain our workflow with the coordinates, hope I don´t confuse you more.

Site.rvt – This model has nothing defined to PBP or it´s orientation. The site is at the model as it is actually.

PBP, SP and origin are in the same location which is know point in real world.

Model.rvt – In this file the PBP and model origin are also in the same location at startup usually some distance off from the intersection of grids.

When I want to start using the site coordinate system I just link the Model.rvt to the site model and then move and turn the link to the correct location.

Small squares represents the models origin (Linked two buildings)

When the move and rotate actions are made then I just click the link and from properties “Shared Site”

I Record the current position to the Model.rvt and click OK. When saving the project it asks:

After saving the coordinates are saved into the Model.rvt

In the Model.rvt the PBP is still in the same location but the SP has moved and the angle to true north has changed.

Now if you export the Model.rvt to IFC with Current Shared Coordinates you can link it to the Site.ifc which is exported with Current Shared Coordinates also. If you export the Model.rvt with Project Base Point you can link it to the Model.ifc

Hope this gives you some idea of Revit´s logic about coordinates. 

[rida_akh]

Hei @KIMRAMFI 

Thank you for your explanation.

I would like to export both the Model.rvt and Site.rvt as PBP and with Project North orientation as IFC file.
While the export of Model.rvt works fine, I'm having an issue with Site.rvt. It always exports with shared coordinates and True North, even after adjusting the settings for exporting and sharing and trying all settings. 

Could you assist me with this issue?