Relocate project to AutoCAD 0,0

[Wes Macaulay]

I have at different points had to help clients move their Revit projects to line up with AutoCAD-generated site plans.

Let's say I've done a pile of work on my project, and now in AutoCAD we've decided that a certain location (say, the intersection of grids A and 1) is going to be 0,0 in AutoCAD for the project.

So I create a circle at 0,0 in AutoCAD and import it into Revit origin-to-origin. It lands somewhere in the project, and now I want to move the project so that grid intersection A1 is at this location, so when I export from Revit to DWG, the consultants can just insert at 0,0 and they're good to go. (This is the offset I describe below - WM)

Been there, done that #1: Relocate this project doesn't do it. Even if I use this command to move the project from its current location to where the origin should be, the Revit export to DWG is still offset from 0,0 the same distance that it was when I imported the DWG into Revit.

Been there, done that #2: I created a world Revit model, if you will, and imported the DWG circle origin-to-origin, then linked in the Revit project and published coordinates back to my project. Same result as #1.

I'm certain that I don't have to start from scratch drawing at 0,0 from the AutoCAD origin, or that I have to use the move tool to move my Revit project to the right place...

How do you do this? David Conant (or anyone else), you're up. I read your post (http://forums.augi.com/showthread.php?t=880)way back when about such things, but the instructions discussed there don't work here.

[FK]

Import using shared coordinates.

[Steve_Stafford]

Wes,
Try working through this tech doc from the Autodesk website. It should help... TECH DOC (http://usa.autodesk.com/adsk/servlet/ps/item?siteID=123112&id=4370512&linkID=3770375)

[mnielsen]

I have tried that as well, along with the methods that Wes has described above. Even publishing the coordinates back to the ACAD file has not remedied this. The export to ACAD option has never brought the revit model back to the same relationship with 0,0 as it was set up.

Since most to all the Survey data that is provided for the projects I have worked on in the last decade are in ACAD format (even if it was generated in another program it was converted into ACAD for the design teams), this is a big issue.

The only way that I have been able to work around this is to always have project origin documented in regards to it's relationship to the World Coordinated System used for the project. This coordinate system may vary due to the different regional survey coordinate systems that are used. Typically we set up the project file so that an intersection of a fixed site element (most commonly used are property lines) is at 0,0. When it's time to export to ACAD an object in REVIT that is aligned with this location (again, usually a property line) needs to be turned on so that it is included with the model. Once that is done you are able to move the drawing entities from that point to it's correct location. Be aware that the rotation may be off if your current view is set to project north, or if the model file's true north has an incorrect relationship to the survey's WCS.

Any divine guidance or remedy is greatly appreciated, always.

[Wes Macaulay]

Import using shared coordinates.If I do this, I get a message stating "The project and the linked file do not share coordinates. The link's World Coordinates will be aligned with this project's Shared Coordinates." If I try to acquire the location, Revit claims it is already syncronised.

Oddly enough, once I've relocated the project by linking it, THEN the AutoCAD 0,0 comes in at the right location.

HOWEVER... when I then export to DWG, the Revit export is still in the WRONG location by the offset described in my initial post.

The bottom line remains: when you export from Revit to AutoCAD, you must have brought in the AutoCAD 0,0 and inserted it origin-to-origin for reference.

If you have not done this, then you are forced to manually place Revit DWG exports every time to line them up with work already done in AutoCAD. This is a hassle! (But it's not fatal, it's just annoying.)

With regards to mnielsen's comments I believe I was told that OpenGL limitations mean that very large coordinate systems cannot be reconciled with the Revit coordinate system. On one large project I worked on, the DWG origin was 200 miles away from the Revit projects! So Revit couldn't deal with that.

Steve, thanks for the link... but that tutorial still doesn't do the trick.

[mnielsen]

I encountered the same issues Wes did.

[Steve_Stafford]

Have you tried this with the latest build then?

[Wes Macaulay]

Affirmative! I'm surprised -- hasn't anyone else noticed this, or needed this capability?

[FK]

"Affirmative" as in it's fixed in the latest build or as in it's not working in the latest build? There is an important bug fix in this area in 20040720_2100 - Revit used to think coordinates were shared when they were not.

If you've got the latest build, try this. Create a brand new dwg with the circle around the origin (Revit may still believe it shares coordinates with the old file). Import it origin-to-origin, place it where you want it, acquire coordinates from it. This will reprime the rvt's shared coordinate system to believe the origin is where you placed it. You may double check with the report coordinates tool. Now export, Revit's shared coordinates should be stored as the UCS...

This all is off the top of my head, if something breaks let's dig more tomorrow...

[Wes Macaulay]

Thanks Fedor -- this is indeed the 20040720 build. You can certainly acquire the coordinates from a DWG as you stated, but when you turn around and export to DWG, the coordinate system does not change in the exported DWG. So if you import a circle drawn at 0,0 into Revit, that location will always be 0,0 (in the AutoCAD WCS) when you export back to DWG even if you change the Revit coordinate system.

This is counter-intuitive: you expect (and want) to have Revit move the world coordinate system in the DWGs it exports.

I would love it if this became a high-priority project. It's extraordinarily bland, but this really makes Revit play nice with AutoCAD. So often people just start drawing the building, and the project origin comes later. Since 0,0 is usually the project origin in AutoCAD projects, and information is inserted with respect to 0,0 between differerent disciplines' DWGs, being able to move the AutoCAD WCS in Revit-exported DWGs when you move the Revit coordinate system is relatively critical.

[Steve_Stafford]

Wes I have a project that Revit will not acknowlege the site plan to acquire coordinates. I'm going to try the new build on it as soon as possible, maybe tomorrow/today...

Revit is able to publish the shared coordinates not only to Revit files but the dwg files as well. It's worked fine for me until this recent topo survey file. There's something in your description of process that's nagging at me, but can't put my finger on it yet.

If it is an issue hopefully we'll get it pinned down soon so it can be fixed before long.

[Wes Macaulay]

Hey Steve... even if Revit is not changing the WCS in its DWG exports out to reflect changes in the Revit coordinate system, at least it can write a new UCS to a DWG you've linked in. However, since most of my clients don't like to use anything but the WCS if they can help it, we'd prefer for Revit to update the WCS on the DWGs it exports.

Is this an arcane conversation or what? :-D

[Steve_Stafford]

...Is this an arcane conversation or what?... Yeah...so to add to that...I think you just need to connect the hoogiewhatsits to the cahndargerfluxor. Then your entervelumizor should run normally again....

[MikeJarosz]

We have been experiencing this problem on the Freedom Tower. The latest build was supposed to fix this problem, and we are testing it now.

It seems with Revit under Autodesk's roof now, there should be no excuse for this kind of incompatibility.

[Wes Macaulay]

Perhaps the idea was to NOT change the AutoCAD WCS and instead use the custom-created UCS that Revit writes back to DWG as the means of sharing coords between Revit and AutoCAD.

Still, I think that Revit should make WCS 0,0 the project origin when it writes out to DWG.

[FK]

I'm confused...

I assume WCS is analogous to Revit's project coordinates (the system in which actual points are defined), and UCS is analogous to Revit's shared coordinates (some global system in which multiple files coexist). Is it right?

Then, are you saying that Revit is not exporting UCS (I was under the impression that it was, but it's not my immediate area), or that the UCS is useless?

It's not a very good idea to define points in terms of huge numbers - you lose precision (not catastrophically though) - so it's preferable (although not imperative) to export Revit's internal coordinates as they are.

[tatlin]

Guys,

Mapping between the Autocad World Coordinate System (WCS ) and the Revit Shared Coordinate System can be divided into two parts - import and export.

The changes in the newest build allow you to do one part of this more easily - the import part. Now you can xref/link any old dwg such that the WCS origin (0,0,0) is lined up with the Revit Shared Location.

This helps for cases where the WCS is required to be in some far away location and you need to link in dwg files for consutants, etc. You all have seen these types of dwgs before - where there is nothing physically at 0,0 and you can zoom extents and see a valid plan, it's just some insane number like 120 miles away from the origin. The easiest test for this is IDing a point or just drawing a line from 0,0 to the building and thus figuring out where the origin is in the dwg.

Ok, so now you can import these kinds of files and not have them end up in space or give you an error message.

It's a good idea when you start new revit projects to draw the project somewhat close to the center of the revit views. If you are starting from dwgs, etc, import something like a plan or even just a column grid using the 'origin-to-origin' import option. I like to use a (hopefully) invarient point like the A1 column line as the 0,0 point in autocad and the same methodology applies in Revit.. If you import a file like this into Revit you should be golden.

Try to use Shared Coordinates to deal with larger numbers and farther away datums, like site benchmarks. The best way to set up Shared Coordinates is with something like a site plan dwg who's WCS is at the common benchmark/datum point. All you have to do is link/import and line up the dwg under your building model (make sure you move and rotate the dwg precisely), then acquire coordinates from the dwg. This sets the Revit Shared Location to be the same as the acad WCS.After you have done this, then you can link in whatever other dwgs you need. They should register correctly and drop right into place.

Great, but this does not anser the main point of the thread, right? I'm getting there...

The other half of this is export. (This is what Wes and Michael, etc are asking for.) Ideally there would be a way to tell revit on export to set the dwg WCS to be in the same place as the Revit Shared Location. This would complete the roundtrip in the preferred coordinate system. Unfortunately, this is not implemented yet but is on our wishlist. If this is important for you, please contact support and let us know (even though we know from reading this thread!). We have only seen this be an issue on projects that require the dwg origin be some large distance from the building.

The workaround at the moment is to write a script in acad that does the correct tranformation (move and rotate).

Does this help explain what is happening currently?

[Steve_Stafford]

Matt,

Excellent summary and thanks for taking the time to say this. Great stuff! I'm grateful for the information and I hope that the new build will help resolve the import issues we've encountered. Count me/us in for the export improvement as a YES! We'll certainly let the support folks know.

[Wes Macaulay]

...Ideally there would be a way to tell revit on export to set the dwg WCS to be in the same place as the Revit Shared Location. This would complete the roundtrip in the preferred coordinate system. Unfortunately, this is not implemented yet but is on our wishlist. If this is important for you, please contact support and let us know (even though we know from reading this thread!). We have only seen this be an issue on projects that require the dwg origin be some large distance from the building.Thanks for the explanation, Matt.

I'm calling support now to register my vote. And I'm going to put a new post in with a poll asking people what they think about having Revit move the WCS 0,0 in the DWGs it exports to be the Revit origin in its coordinate system.

[sbrown]

There is no doubt we need this in a big way. Any job with multiple buildings that is going to need to be coordinated with a set of civil drawings needs this functionality. Or the ability to specify on export the point you want to be 0,0,0 . But basically this one should work identical to autocad for obvious reasons.

[FK]

OK, I'm unconfused now. ;-) I was under the false impression that Revit writes out shared coodrinates on export. That part has not been implemented.

You can try this shrewd trick just for the heck of it. After setting up shared coordinates and exporting your model, link your newly made export back into your model origin-to-origin, publish shared coordinates into it, save. This should write a named coordinate system into the file that will correspond to shared coordinates, if I understand things correctly...

[sbrown]

The whole shared coordinate business makes my head hurt. I think this is like the begining of worksets where it was totally "unRevit" When you start talking about, publishing, sharing, WCS, import/export..., then link and maybe just maybe this will work. Now think about a job with 60 buildings (all sep bldg files) on a site that you have to do this for and you will see the problem. Please developers take a look at a simple way to find the 0,0,0 of a civil plan and create an insertion point for each building you are working on without this major PIA.

I remember bragging about my previous boss who couldnt use Autocad to save his life, did an entire building in Revit in Release 2 and only asked me a few questions. Some of the ease of use is getting lost.

If shared coordinates is the answer, some sort of wizard should be developed to walk the user through the process.

[FK]

We hear you, we feel you...

[Wes Macaulay]

The whole shared coordinate business makes my head hurt... I remember bragging about my previous boss who couldnt use Autocad to save his life, did an entire building in Revit in Release 2 and only asked me a few questions. Some of the ease of use is getting lost.

If shared coordinates is the answer, some sort of wizard should be developed to walk the user through the process.Shared coordinates is a totally intangible and confusing concept. Why is it warmer in the summer than in the country? But the UCS and WCS is just as bad.

Revit is becoming a more feature rich program. As a result, there's more to learn. But what can we say? We asked for these features -- we need them to do our work!

[jpolding]

"Affirmative" as in it's fixed in the latest build or as in it's not working in the latest build? There is an important bug fix in this area in 20040720_2100 - Revit used to think coordinates were shared when they were not.

If you've got the latest build, try this. Create a brand new dwg with the circle around the origin (Revit may still believe it shares coordinates with the old file). Import it origin-to-origin, place it where you want it, acquire coordinates from it. This will reprime the rvt's shared coordinate system to believe the origin is where you placed it. You may double check with the report coordinates tool. Now export, Revit's shared coordinates should be stored as the UCS...

This all is off the top of my head, if something breaks let's dig more tomorrow...

I'm working with R8 trying to reproduce what you have stated here. I can't seem to get past acquiring the coordinates from the dwg. It's not even recognizing the dwg when it asks me to select a linked project.

[JamesVan]

Your DWG file is probably an import, not a link. Do you see the DWG file under File-Manage Links?

[FK]

Forget what I said back then! I've implemented the "specify coordinates at a point" tool since.

[jpolding]

When I export to dwg it still doesn't come in at 0,0,0. That's using the "specify coords at point" tool.

[FK]

In export options, set coordinate system basis to shared.

[jpolding]

Yes, that worked thanks. :-)