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Discrepancy in Linked CAD in Revit vs Autocad.Possible Bug?

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stingers80-cgarchitect
2026 Aufrufe, 32 Antworten

Discrepancy in Linked CAD in Revit vs Autocad.Possible Bug?

Hi Everyone!

 

There are really scary stuff happening with a Site plan that I am working on. When I Link survey CAD file into Revit, some objects are misplaced. I have tried moving the whole survey CAD file close to Autocad origin and remove and reload it in Revit. Still the same.

So here is a screenshot of differences in Cad and Revit:

same cad file in Revit vs Autocadsame cad file in Revit vs AutocadCapture-2.PNG

 

 

 

 

 

 

 

 

on the right screenshot, I added a circle around fire hydrant and it showed up correctly in Revit but the Fire hydrant

is still misplaced.

It seems that changing the view to True North sometimes puts Fire hydrant back in place but it's all random.

 

What is going on here?

 

Edit: this is Revit 2019

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Nachricht 2 von 33

So, to clarify: the CAD shown on the right side is Linked into Revit shown on the Left side?   Are you sure you Linked the correct CAD file? Reason I ask, is  because not all the CAD elements shown in the screenshots are appearing in the Revit screenshots. 

 

That is weird behavior.   Can you ZIP and post the DWG? 

Nachricht 3 von 33

I could somehow pinpoint what is causing it:

If I reload CAD file in Revit while View is in 'True North', things will go off.

Also, Linking it while you are in 'True North' vs 'Project North' will sometimes change the behavior.

This is freaking me out

 

I attached cad and a simple revit project that I just created.(try reloading cad while in True North view)

Nachricht 4 von 33

I tried several Tests with you files and cannot replicate on my end.  Scratching my head here.  Let me confirm my understanding. A Block Reference in the DWG is located in a different location when the DWG is Linked into Revit. Is this what you are saying?  

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hmunsell
als Antwort auf: stingers80-cgarchitect

I couldn't duplicate the issue either, I'm using Revit and AutoCAD 2020. check your blocks.

 

one thing I did notice is the insertion and 0,0 location in the FYHD block there way off. Typically, unless required otherwise, the Insertion Base Point is at or near the 0,0 location.  id check any other block that jumps around too.

Capture.JPG

Howard Munsell
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did you try this?

-open that revit file

-change orientation to 'True North'

-Manage Links > reload CAD

-Cad file will be rotated (which is natural)

-fire hydrant will jump out of its place

 

I replicate it again just now

Capture.PNGCapture2.PNG

 

second picture is after CAD reload

Nachricht 7 von 33
stingers80-cgarchitect
als Antwort auf: hmunsell

CAD insertion point maybe a problem.

But I see this as a bug at the very core of the revit.

We receive CAD files from consultants all he time. I can't go through them. Doesn't make sense

 


@hmunsell wrote:

I couldn't duplicate the issue either, I'm using Revit and AutoCAD 2020. check your blocks.

 

one thing I did notice is the insertion and 0,0 location in the FYHD block there way off. Typically, unless required otherwise, the Insertion Base Point is at or near the 0,0 location.  id check any other block that jumps around too.

Capture.JPG


 

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Nope. Still behaves.  

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@barthbradley wrote:

I tried several Tests with you files and cannot replicate on my end.  Scratching my head here.  Let me confirm my understanding. A Block Reference in the DWG is located in a different location when the DWG is Linked into Revit. Is this what you are saying?  


Yes. That's exactly what's happening.

Btw, tried it in revit 2020.2. Same result

Nachricht 10 von 33

The file appears to be using Meter for the base unit. The WCS (World Coordinate System) is oriented with the site at an angle. The file is using a UCS and Snapang to rotate it horizontal. Revit ignores that, it only references the WCS.

 

When I link the file using Meter as base unit it appears to be working properly to me, similar to the others. The fire hydrant block looks the same to me in either software.

 

If you rotated the DWG in Revit and used Acquire Coordinates you need to maintain Project North in the view the file was linked into originally. Changing it to True North and then reloading the DWG will cause it to rotate out of position. You can assign any other plan view to True North just not the one the DWG file was linked into originally.


Steve Stafford
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ToanDN
als Antwort auf: stingers80-cgarchitect

The CAD geometry is way too far from the WCS 0,0,0 so you need to link it in Center to Center to avoid any distortion.  Then acquire the coordinates from it to establish the Survey Point location and True North.  There is no need to set the True North in the Revit file by yourself. 

 

I tested with above workflow and everything is in order.

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My observations are consistent with @ToanDN.

 

My last paragraph is relevant (the rotation in your screencast) when you link a survey file into the building model (I always use a separate model for site personally) and then define True North. The view used to link the DWG needs to remain assigned to Project North so Revit can refresh the DWG during reload or open the Revit project file and maintain it's position properly.

 

If you're interested I wrote four posts running through this process (4th post deals with the rotation issue).

2015 Survey Point - Post 4 - Acquiring Coordinates and View Orientation
2015 Survey Point - Post 3 - Five Minutes with Shared Coordinates
2015 Survey Point - Post 2
2015 Survey Point 1


Steve Stafford
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Could you duplicate the problem on your end following what i did?

 

I do agree with your points about True North, Shared coordinates,..

We have a lot of projects that are already setup without shared coordinate and honestly I don't want to bring the idea of Shared coordinates to the office at this time because of level of Revit knowledge of team members.

 

Bringing in a CAD file is the simplest thing I need from Revit.

This issue was brought to me from another team member and I think without extensive knowledge of Shared coordinates they should be able to simply link a Cad file and rotate it without things flying around.

 

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I can replicate a DWG rotating wrong after defining True North all day long...

 

You can link a CAD file and leave it in its default orientation and it will stay put regardless of True or Project North. However as soon define True North you must set and maintain Project North orientation in the view you linked the DWG into originally.


Steve Stafford
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barthbradley
als Antwort auf: SteveKStafford

The OP is talking about an isolated Block Reference moving inside the DWG Link-- independent of the DWG Link as a whole.  Are you saying that you can replicate this "all day long"? 

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to reiterate my point, I don't have a problem with rotating a DWG.

However if some elements inside DWG are misplaced, that seems like a bug to me.

Nachricht 18 von 33

That didn't happen to me in either my own linking of your DWG or opening your RVT file.


Steve Stafford
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Open a support case with Autodesk and submit that screencast as evidence. Let us know what they say. I'm curious.  

Nachricht 20 von 33

Let me back up... the block issue is related to the rotation that happens because True North is defined and the reload causes the file to be regenerated in a different position. The file's elements are very far from the origin of the WCS, which is normal for a survey. The block issue is "bad" but the rotation is a bigger problem no? It is no longer oriented correctly with respect to the "building". The solution to the rotation AND the block issue is to prevent Revit from rotating the DWG after True North is defined.

 

Revise the DWG and reload it any time you want. Just leave the view it was linked into originally assigned to Project North and you won't have the block issue either.

 

Bug? I suppose so but they know about this and it has worked this way forever...


Steve Stafford
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