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Thread: Xref Confusion: Attachment or Overlay?

  1. #1
    I could stop if I wanted to Mamma Jamma's Avatar
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    Default Xref Confusion: Attachment or Overlay?

    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.

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    AUGI Addict kennet.sjoberg's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    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

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    I could stop if I wanted to Mamma Jamma's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    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.

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    I could stop if I wanted to LanceMcHatton's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    Quote Originally Posted by lafleur
    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.

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    I could stop if I wanted to H.Hunter's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    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 .

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    I could stop if I wanted to LanceMcHatton's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    Quote Originally Posted by H.Hunter
    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.

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    I could stop if I wanted to Mamma Jamma's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    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.
    Last edited by Mamma Jamma; 2006-03-17 at 02:13 PM.

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    I could stop if I wanted to H.Hunter's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    Quote Originally Posted by lafleur
    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.

    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.

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    I could stop if I wanted to Mamma Jamma's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    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....

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    AUGI Addict kennet.sjoberg's Avatar
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    Default Re: Xref Confusion: Attachment or Overlay?

    . . . hmmm
    Quote Originally Posted by kennet.sjoberg
    . . . but the main thing is good organization.

    : ) Happy Computing !

    kennet

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