Linked ACAD "winks out" on zoom

[damon.sidel]

I have two problems with some linked ACAD drawings in my Revit project (besides the fact that they are there in the first place, but don't get me started).

1. Some, and I emphasize some, linked ACAD drawings disappear when you zoom in on them. For example, we have a detail section, turn off the Revit model, link and place an ACAD drawing. Looks OK. Then zoom in and the ACAD disappears! Zoom back out and there it is. If you select the ACAD file so it is highlighted blue, then zoom in, no problem. This is on multiple machines with different graphics cards. We've tried turning off the hardware acceleration.

2. Dimensions added in Revit referencing ACAD lines get deleted on reload and sometimes even on just opening the project. Any thoughts? Is there a way to dimension in Revit on an ACAD link or should all dimensions for that ACAD drawing be done in ACAD?

And just for the record, I know this could all be solved by not using ACAD drawings in our Revit file. I'm also going to state up front that we are not going to convert the ACAD to Revit by tracing over the views or any of the other options like that even though that would be better. We're stuck with the system we have for now because of staffing.

[jj mac]

Have you tried exploding the CAD files?

[damon.sidel]

No, but I think that that is a non-starter. The ACAD is a link, not imported, and we have to be able to maintain the link to reload any changes.

[Brian Myers]

Damon,

1. This might be an odd question, but it needs to be asked. Are you certain all the Revit entities are turned off? Are they hidden manually or by shutting off all the Revit entities under Visibility Graphics? I ask because I've seen this occur when objects exist on the same plane. Revit doesn't know which to display so it seems to randomly display entities depending on the zoom factor. So, if a Revit object is still on then it could be hiding the AutoCAD information.

2. Are changes made to the AutoCAD object? If so, then the dimensions might delete themselves when it can't find an entity with the appropriate ID number linked into the Revit project. For instance, a line is deleted in AutoCAD then redrawn... *poof* it looks good in AutoCAD, but it's now gone in Revit.

To answer your other question: If the AutoCAD drawings are changing then I would dimension those drawings in AutoCAD. If it's an option, I wouldn't even bother bringing them into Revit if the entire detail sheet is done in AutoCAD, print the sheets from AutoCAD as it might provide a better quality output. Obviously this might NOT be an option depending on the view and/or sheet, but since I can't see your set I'm just talking in generalities.

[damon.sidel]

Brian, thanks for your reply.


1. This might be an odd question, but it needs to be asked. Are you certain all the Revit entities are turned off? Are they hidden manually or by shutting off all the Revit entities under Visibility Graphics? I ask because I've seen this occur when objects exist on the same plane. Revit doesn't know which to display so it seems to randomly display entities depending on the zoom factor. So, if a Revit object is still on then it could be hiding the AutoCAD information.

Interesting, I've never seen this version of what sounds like z-fighting in Revit in this way. I just checked and the Revit model stuff is hidden in two ways: either under Visibility/Graphics or with the view property Display Model set to "Do Not Display". And the ACAD info is set to foreground.


2. Are changes made to the AutoCAD object? If so, then the dimensions might delete themselves when it can't find an entity with the appropriate ID number linked into the Revit project. For instance, a line is deleted in AutoCAD then redrawn... *poof* it looks good in AutoCAD, but it's now gone in Revit.

Yes, the ACAD stuff is being changed and I can understand that that particular dimension would get deleted. However, on reload ALL the dimensions are deleted, even if only a small, unrelated change was made to the ACAD file.



To answer your other question: If the AutoCAD drawings are changing then I would dimension those drawings in AutoCAD. If it's an option, I wouldn't even bother bringing them into Revit if the entire detail sheet is done in AutoCAD, print the sheets from AutoCAD as it might provide a better quality output. Obviously this might NOT be an option depending on the view and/or sheet, but since I can't see your set I'm just talking in generalities.

Good idea, I guess we'll keep the dimensions in ACAD. As for not bringing them into Revit, that's a possibility, but we like the ability of Revit to keep track of the references, so we make sections and elevations, hide the model, then link the ACAD. That way we also get the sheets all in Revit for organization/management/printing purposes.

[Duncan Lithgow]

another cause I've seen is where the part of the acad file you're linking in is a long way from the drawings ucs (or maybe it was the drawings center). anyway, you get the picture - check the files geometric size.

[damon.sidel]

another cause I've seen is where the part of the acad file you're linking in is a long way from the drawings ucs (or maybe it was the drawings center). anyway, you get the picture - check the files geometric size.

Good thought, but I checked one of the offending drawings and that is not the case. The drawing is near the origin and I can't find anything that is far away (even the few blocks seem to have reasonable origins). I continue to be stumped.

[Brian Myers]

Interesting, I've never seen this version of what sounds like z-fighting in Revit in this way.
It's pretty easy to reproduce if you use a floor and a wall, particularly a brick wall. Take a look at this example (yes, zooming in/out changes where the brick/gray show up):

87426

That being stated, try shutting off everything (except for the AutoCAD info) under Visibility Graphics (VG). You stated earlier that items were turned off a combination of ways, I'm just verifying they are turned off entirely in VG.

Other than that, I'm uncertain without looking at the file....

[damon.sidel]

To clarify, I've seen z-fighting in Revit as you show, just not between an ACAD file and the Revit model. Thanks for the suggestions, I've tested the variations of how to turn off the model, so I don't think that this is the problem.

[damon.sidel]

An update (and hopefully some more ideas for a solution?): The linked ACAD file "winks out" when the crop region tries to crop out any portion of the ACAD drawing. It also winks out when I pan around the drawing such than any portion of it starts to go out of the window. Any new thoughts?

[JamesBaker]

Hardware Acceleration turned on or off? sounds like its just a graphics card (hardware) issue maybe?