Xref Confusion: Attachment or Overlay?

[Mamma Jamma]

the following is an email I sent out to our users. We cover many disciplines and, since we have quite a few new people with varied backgrounds, we've been having issues regarding the use of Attachment vs. Overlay.


Here’s a simplified example of our standard xref structure:

Drawing PP1.0 references ppxref, which references pmxref, which references axref.

In the above scenario, it is necessary for all of the references to be attached using ATTACHMENT, not OVERLAY.

WHY?

Well, let’s say that the pmxref has been brought in to the ppxref using the Overlay option. When you are working in the ppxref, you will see all the lovely equipment that is on the pmxref. However, when you subsequently attach the ppxref to PP1.0, you will NOT see the pmxref. All the equipment will have disappeared, and pmxref will not appear in the list of xrefs. Or, if you had used overlay to bring the architecture in to the pmxref, you wouldn’t see the building on ppxref.

OVERLAY-ed xrefs do not nest.

There IS a valid use for the Overlay option. If you need to reference a drawing, but not have it show on other drawings down the line, that is the time to use Overlay. This could simplify the whole Unload/Reload business that seems to be happening on some of our drawings.

[kennet.sjoberg]

The advantage with overlay is that you can cross ref files without forcing AutoCAD into an endless loop, overlay breaks the third “visual link”.
You can OVERLAY three files in a circle, but if you ATTACH three files in a circle you are in trouble.
There is more than one way to handle this, but the main thing is good organization.

: ) Happy Computing !

kennet

[Mamma Jamma]

:) Yes, that's true. It's an additional use for Overlaying xrefs. I didn't mention it because it doesn't apply with our preferred way of working with them.

[LanceMcHatton]

:) Yes, that's true. It's an additional use for Overlaying xrefs. I didn't mention it because it doesn't apply with our preferred way of working with them.
Just a little note on XREFs: Anytime you XREF one drawing into another, you take a chance on also bringing errors into your drawing from the other drawing. I understand that ATTACH is better for your company, but please be aware that when you start nesting your XREFs, you will have a greater chance of having hard-to-solve problems that could render your drawings useless.

We use OVERLAY when bringing XREF-type drawings into other XREF-type drawings. However, when we want to XREF dwgs into the sheet files, each and every XREF-type drawing is individually brought in. this can be done using ATTACH or OVERLAY. It doesn't really matter in this case.

We had a problem just recently where one XREF had some errors in it because we weren't keeping on top of it's regular cleaning (audit and purge). It started causing problems with our other XREFs only we didn't know which drawing was bad. We spent about a half-hour tracking it down by detaching XREFs from other XREFs. While tracking it down, we needed to plot an impromptu set of plans for the client. If we had used nested XREFs to build our sheet drawings, we would have seriously upset the client with a delay.

ATTACH and OVERLAY both have their places and it's not necessarily a bad idea to have mixed use.

[H.Hunter]

We use overlay 90% of the time here. The only time we use attach is for arranging structures on a site plan so they stay in fixed locations that everyone can reference. Otherwise, we have everything else overlayed to minimize filesize and dragging in unwanted xrefs in other drawings. Also, until recently AutoCAD didn't like circular xrefs, which attaching xrefs made that problem very annoying. So overlay is a nice to solve that problem.

A note to Lance's response: Errors can be brought in via overlay or attach (trust me on this...) from an xref. However, if you audit a sheet, it will tell you what xref it lies in (right before is tells you what the errors are) so you can easily do an xopen and audit that file to clear the error(s) and reload the xref.

Now if we can just get '07 to use that new xref manager :cool:.

[LanceMcHatton]

A note to Lance's response: Errors can be brought in via overlay or attach (trust me on this...) from an xref. However, if you audit a sheet, it will tell you what xref it lies in (right before is tells you what the errors are) so you can easily do an xopen and audit that file to clear the error(s) and reload the xref.
Right. I wasn't saying that OVERLAY eliminates errors. I was trying to say that people will have fewer problems with errors and troubleshooting the errors if XREFs are set up with OVERLAY.

[Mamma Jamma]

Yes, all good points. But when we are creating, say, our process piping or electrical sheets, it would be really crazy to have to start attaching every xref individually to each one, when we need to see everything on all of them, beginning with the architecture and building on up through the process equipment to the piping, electrical, etc. Generally, our base is axref + pmxref + discipline specific xref which is then brought in to the individual drawings. All attached rather than overlaid. If there's a problem, it's simple enough to open each of those refs in turn, beginning with the base - which, logically, is the building - audit/purge/etc. Then clean xrefs are brought in to each subsequent level when it's opened or reloaded.
The only real problem we've had is with people inadvertently using overlay rather than attach and not realizing the consequences down the line...not knowing that someone else opening a higher level drawing wouldn't be seeing that xref.

[H.Hunter]

Yes, all good points. But when we are creating, say, our process piping or electrical sheets, it would be really crazy to have to start attaching every xref individually to each one, when we need to see everything on all of them, beginning with the architecture and building on up through the process equipment to the piping, electrical, etc. Generally, our base is axref + pmxref + discipline specific xref which is then brought in to the individual drawings. All attached rather than overlaid. If there's a problem, it's simple enough to open each of those refs in turn, beginning with the base - which, logically, is the building - audit/purge/etc. Then clean xrefs are brought in to each subsequent level when it's opened or reloaded.I guess we're crazy then. :cool:

I just Ctrl+Click all the xrefs when I create the sheet and insert them all at once. Now if we used Sheet Sets, that could turn into another story. I haven't had the time to research exactly how the SSM works with extensive xref schemes.

[Mamma Jamma]

:) tomato, tomahto...

It's really a question of what works in your circumstance. I just found that lots of folks here didn't realize the difference between attaching and overlaying.
Then there's the issue of people inserting the xref on a non-plotting layer or layer that will subsequently be frozen...
It's always something. You'd think after I "fixed" it for them once, I wouldn't have to come back to them for the same problem 2 days later....

[kennet.sjoberg]

. . . hmmm

. . . but the main thing is good organization.

: ) Happy Computing !

kennet

[Mamma Jamma]

:roll: yeah, good organization...

Unfortunately, the organization/standards we DO have get ignored by some (who I don't have the power to fire or beat). Can't really say by "rogue" operators since that implies actual thought and intent, which might be an improvement... :banghead:

[r.grandmaison]

[COLOR=Navy]
There IS a valid use for the Overlay option. If you need to reference a drawing, but not have it show on other drawings down the line, that is the time to use Overlay. This could simplify the whole Unload/Reload business that seems to be happening on some of our drawings.

Once an Xref source file has been attached, the attachment option (attachment/overlay) can be changed by double clicking it (attach/overlay) in the Xref Manager.

A really good example of when to use Overlay is if you're getting files from a client and you want to OVERLAY their file atop yours for making adjustments to your drawing, or comparing changes, etc.- but don't actually use their drawing (they never know how to draw very well or ever practice good layering!) Well, by OVERLAYing their file into your file, you're free to ATTACH your file into any of your plotting sheets withoug bringing their messy work into your pretty work!

Cheers,

Robert

[Hammer.John.J]

being in civil/la we never attach because our drawings all reference each other so we could never do them as attachments

i should say there are times we get supplement survey or some utilities and we do ATTACH that file to our survey.

[sschramm]

This very topic has arisen in my company where we have a monthly CAD Standards meeting. Unfortunately, I missed an unofficial impromptu meeting where it was decided that from now on, we ONLY use the OVERLAY selection when attaching xrefs. I have thoroughly researched the differences between ATTACH and OVERLAY and know when to use what. However, there is a mountain of anecdotal evidence by my coworkers that things "just go bad" when you attach. I hear horror stories of frozen base files, destroyed completely, base files with multiple entities (I think the culprit here was REF EDIT), and a great fear of circular references, though it does warn you now if you have a circular reference. Personally, I've always ATTACH-ed (except when I choose to overlay) and have had no problems.

We are a firm that works with other firms that vary in a full spectrum of experience. In many cases, we get drawings that are scaled, rotated, and moved in all sorts of ways. I prefer to ATTACH and make the adjustments once, in one drawing. In addition, these drawings are changing as we design and we get updates frequently, naming the new drawings the same to avoid having to repath. The alternate solution is to put what you did on defpoints in the base drawing ("move a,b,c to x,y,z, rotate xxdegrees, scale xxx"). Ugh.

I think that education is the best answer, which is difficult in a rapidly-growing company, but my coworkers feel that an all-or-nothing approach is better. I've tried but the horror stories ensue. Any advice?

[Hammer.John.J]

suggestions...

you have 3 drawings A,B, & C, then D is added at the end of all the setup.

A is overlayed into B
A & B are overlayed into C
A & C are overlayed into B
B & C are overlayed into A (but do not print, no plot layers)

say D comes along and needs to be supplemental to A, and therefore B & C. this is a good time to "attach" D into A if you don't intend on inserting the raw data as drawing objects into A, and you only want to reference the supplemental info. All other instances should be "overlay".

[philpiper]

Our policy is to OVERLAY all raw data files and only to use ATTACH when compiling final drawing sheets that will be plotted. The logic is as a number of people have already suggested - it minimizes the problems of forming chains that reference themselves and data showing up on final drawing sheets that shouldn't be there because someone has ATTACHED a file somewhere back down the line.

[framedNlv]

A really good example of when to use Overlay is if you're getting files from a client and you want to OVERLAY their file atop yours for making adjustments to your drawing, or comparing changes, etc.- but don't actually use their drawing (they never know how to draw very well or ever practice good layering!) Well, by OVERLAYing their file into your file, you're free to ATTACH your file into any of your plotting sheets withoug bringing their messy work into your pretty work!

Cheers,

Robert

Wow!!! I hope these are not my files you are referring to. I do work for a consulting firm and am proud of our work (including our layering).

I (we) overlay all files that do not belong to us (period). I would suggest as mentioned above that you should overlay any file that is not yours.

Example that I run across often is receiving updated files that have our work attached with our nested xrefs unloaded. Now when I open MY file with MY xref it will be unloaded and will not stay loaded (after reopening) because of what someone did with a file they didn't create in the first place. I don't know if this still applies in 2008 version.

Chris

[framedNlv]

Our policy is to OVERLAY all raw data files and only to use ATTACH when compiling final drawing sheets that will be plotted. The logic is as a number of people have already suggested - it minimizes the problems of forming chains that reference themselves and data showing up on final drawing sheets that shouldn't be there because someone has ATTACHED a file somewhere back down the line.

That would work for us when we receive these type of files. We typically will overlay the Architectural sheet so our files will match and pick up any new xrefs.

Chris

[richardarchitect]

ok as the architect, i have been providing my consultants with dwg files via our ftp site. Our xrefs are all no path attached, which i feel gives our consultants the same ability we have to unload xrefs as they see fit to create their drawings and sheets. Each of our sheets is developed individually by xrefing in what is required on that sheet. Granted this method brings in many unecessary xrefs, but by creating each sheet as a seperate dwg, it gives us the ability to reload xrefs temporarily to look at other aspects of a particular design challenge. I guess I am wondering how this method impacts on the process from your end? Dang I can't edit this to add a quote, I was replying to Sue.

[richardarchitect]

Wow!!! I hope these are not my files you are referring to. I do work for a consulting firm and am proud of our work (including our laying).

I (we) overlay all files that do not belong to us (period). I would suggest as mentioned above that you should overlay any file that is not yours.

Example that I run across often is receiving updated files that have our work attached with our nested xrefs unloaded. Now when I open MY file with MY xref it will be unloaded and will not stay loaded (after reopening) because of what someone did with a file they didn't create in the first place. I don't know if this still applies in 2008 version.

Chris

Hey thx for the heads up Chris, that makes perfect sense. All consultants drawings will be overlays in the future at my firm

[richardarchitect]

:roll: yeah, good organization...

Unfortunately, the organization/standards we DO have get ignored by some (who I don't have the power to fire or beat). Can't really say by "rogue" operators since that implies actual thought and intent, which might be an improvement... :banghead:

my boss just says "KILLEM"

[richardarchitect]

my boss just says "KILLEM"

Are those standards in written form? That is what I am about to embark on.

[Yancka]

I've been using OVERLAY method mostly. And since today I thought it was fine. Now I have to change plenty of xrefs from OVERLAY to ATTACHMENT (to meet the goal of having all information stored in one place as much as possible).We had a little discussion on this subject in our office and the conclusion was: use ATTACHMENT always except when you know for sure that you don't want this particular xref to be nested in next level references.

I believe in large offices this would create chaos, since few people would commit mistakes... what else we do to avoid mistakes, is having special layer (locked) for xrefs.

[p.eddington]

With regard to xrefs what I really want is something that tell you which drawings a dwg file is used in as an xref

[jaberwok]

With regard to xrefs what I really want is something that tell you which drawings a dwg file is used in as an xref

The search function inside the Design Centre can do that for you.

[dgladfelter]

I understand each firm works differently, but in my firm (a Civil firm) our preferred method is OVERLAY. We are a full-service Civil/Survey firm of about 350 employees. Thanks to a strong CAD Standard we have been able to promote a great amount of inter-departmental collaboration.

Before we had a single, unified CAD Standard, each department did their own thing. Now that everyone uses the same layers, blocks, text styles, etc, we can actually share between departments. Especially in larger projects, it's not uncommon to have our Site Development, Transportation, Public Utilities, and Landscape Architecture departments working together on multiple parts of a project. Generally speaking everyone is going to reference the master C-SPLAYO dwg, but not everyone (say Landscape Architecture) is going to need to reference our C-SPUTIL (utility) drawing.

We have promoted an a-la-carte approach to XREF's. As the CAD Manager that has to support those users, I can say at least 90% of my xref related support requests have had to do with Attached xref's. Since you only reference what you need for a given sheet, the errors are reduced, and when they occur the RECOVERALL command in ACAD 2008 most often fixes the problem rather quickly.

[dom.187380]

I learned the hard way about the difference in Attaching vs. Overlaying an xref. Ss there a method to simply convert xrefs of one type to the other?

Dom
v. 2009

[LanceMcHatton]

I learned the hard way about the difference in Attaching vs. Overlaying an xref. Ss there a method to simply convert xrefs of one type to the other?

Dom
v. 2009
Go to the Xref Manager where it lists out your xrefs. Click on the xref you want to change. At the bottom, you will see the xref info. Click where it says either OVERLAY or ATTACH and then click on the down arrow on the right to change it.

[dom.187380]

That's the ticket. Many thanks.

dom

[archie.manza]

Here we go - Attach versus Overlay... this means two different way of working. If you chose "ATTACH" you have to learn to unload unnecessary xref's and learn the consequences of binding it (if you can). But if you use "OVERLAY" all you have to do is have patience of xrefing. What I'm saying is like our company we have base and sheets. And most of the time (due to laziness) some drafters will attach it to their base so that it will come to their sheets. So the other discipline will xref their base which will create a Circular Reference. I concluded that "Overlay" should be used in a multi-discipline company and "Attachment" should be use if there are no other discipline(s) are involved.

[Opie]

I concluded that "Overlay" should be used in a multi-discipline company and "Attachment" should be use if there are no other discipline(s) are involved.

You can set the XREFTYPE to 1 for new xref's to default to overlay. This variable is set within the registry, so you won't have to worry about it being different in each drawing.

[baker.d]

:) tomato, tomahto...

It's really a question of what works in your circumstance. I just found that lots of folks here didn't realize the difference between attaching and overlaying.
Then there's the issue of people inserting the xref on a non-plotting layer or layer that will subsequently be frozen...
It's always something. You'd think after I "fixed" it for them once, I wouldn't have to come back to them for the same problem 2 days later....

Cheer up things could be worse; sure enough I cheered up and things got worse. As System Admin and Cadd Management I find all too often I have become a walking notepad, which is to say it is easier for some of our technicians and intern architects to not have to remember how to draw a line, but rather ask me time and time again. Obviously the "drawing a line" issue was employed here to drive the point. The point being unless you have in place a system of standards that is overseen by the Gestapo and as such the Gestapo provides severe beatings and imprisonment for those who don't tow the line then you will constantly have people doing their own thing no matter how much you try to keep things in order there will always be someone that messes something up. The nature of the beast.

[irneb]

Very true! We do have "standards" but then they're considered by most to be more like "suggestions" :roll: ... partly, because the main honcho's who oversee these meetings have never in their life used ACAD. So the standards are at worst cr@p or at best inconsistent / incomplete. That's probably why everyone just uses them as suggestions. If you do have the Gestapo, then they need to be enforcing something which actually works!!!

BTW, I'd say the debate about OVR/ATT is more of a method of working. It all depends on your scenario. If your work doesn't comprise several portions of a building plugged into several places on several other drawings (e.g. hotel guestrooms repeated numerous times on numerous levels) then you probably don't have the need for attach. Conversely if you force OVR on this scenario you end up having to place each room on each drawing showing those rooms, e.g. with RCP's (Reflected Ceiling Plans), Tiling/Finishes Layouts, Fitting Layouts, etc. you would have to reOverlay each and every room in it's correct spot, rotation & mirror state. If you have ATT then you don't need to do this more than once in the 1st drawing.

All that said, there are definitely situations where ATT makes life difficult. One example (of many):. say you have 3 drawings: A, B & C. A is attached to B. B is attached into C. A is overlaid into C as a second version (for reference or whatever). Now try overlay/attach C into another DWG. Both the instances of A will show up, even though the 2nd should be overlaid. I've come across this arrangement, but find it extremely difficult to reproduce - seeing as you need to overlay A into C before you attach B, otherwise A will become an attachment in C (as it's going to be anyway).

As for errors brought into a DWG from other xrefs, I find ATT/OVR doing much the same in that case. It's when the nesting causes errors in itself that you have to worry about ATT/OVR. Moral: always keep your DWG's as clean as possible. But that's not just a moral for XRefs is it?

So to be blunt: if your staff are a bunch constantly causing I-D-10-T errors, then use some piano wire nooses to get them to ONLY USE OVERLAYS. If your staff seem to have an acceptable IQ and can actually draw a line on their own, you may start looking at making your method more efficient.

[mace]

From my experience it is better to ‘Overlay’ than ‘Attach’. When you use attach, whoever attached your drawing gets attachment too.

[irneb]

Welcome to AUGI & congrats on your 1st post.
From my experience it is better to ‘Overlay’ than ‘Attach’. When you use attach, whoever attached your drawing gets attachment too.Yes, but sometimes that's exactly what you want. ;)

My point is, you can't simply have a blanket statement of Overlay only. You should rather try to think about what works and how efficient it is. Each scenario may thus cause you to use either overlay or attachment, depending on the situation. My personal rule of thumb is: "Rather overlay, unless you can see benefit in attaching or if you can see you need your xref to be nested."

[madyvette]

Welcome to AUGI & congrats on your 1st post.Yes, but sometimes that's exactly what you want. ;)

My point is, you can't simply have a blanket statement of Overlay only. You should rather try to think about what works and how efficient it is. Each scenario may thus cause you to use either overlay or attachment, depending on the situation. My personal rule of thumb is: "Rather overlay, unless you can see benefit in attaching or if you can see you need your xref to be nested."
I agree, the combo of the two for best results.
I do Piping. Every line is modelled in an individual file. We Overlay other disciplines (Steel, Mech...) as reference.
The only time we attach is when creating the full model of an area, and then the full model of the Process Plant.
Every discipline does the same, so at the very end you have your Master Model with one attachment from each discipline.
Also, when you Overlay, the file seems to be smaller than Attaching, and trust me, I have wasted lots of time waiting for a drawing to open because someone had gone nuts Attaching things.

[PinoyAko]

Thanks for sharing this tips.... Overlaying is much more convenient than Attaching xrefs.. :)