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Large distances still a problem in Revit 2008

PostPosted: 16 Apr 2007, 17:20
by David Howe
Drawings with data located a long way from the origin still don't import properly even when link settings are set to 'center to center'.

I thought one of the reasons for the 'rewrite' of Revit was in order to fix shortcomings in the data structure.

It is getting harder and harder for any firm working with clients such as the NSW Govt, SACL, etc who require projects in MGA coordinates, to take the product seriously. Hell, even your average survey for an alts and adds is likely to be set out to MGA.

Maybe it will be in next year's release: Revit Architecture 2935...

As I wrote in the wish list last year:

64 bit floating point accuracy
Autocad has it, why doesn't Revit?

This is a must have for anyone working with clients (Govt, SACL, etc) who require projects to be located in MGA coordinates.

Most surveys and GIS information are in MGA format. All of the large projects I've worked on in recent years have been set up to MGA, often as a client requirement. All of the construction documentation at my current office is to MGA coordinates.


Floating Point Accuracy

PostPosted: 13 May 2008, 18:39
by chrisneedham
I realise this won't constitute a great answer as it is only a workaround, but are you using scripts to automate the 'movement' of your exported/imported geometry?

If not, it's a great way to make the best of a bad situation. The drawings can be batch-processed, then, so that the time taken to effect this change is minimised, and is effectively only a couple of seconds per drawing...

(HINT: Ensure that in the script you include the thawing and showing of all layers so as not to leave anything behind in the old location...)

PostPosted: 16 May 2008, 15:51
by David Howe
Scripts, thawing, layers... Are we still talking about Revit?

I realise you mean performing a batch move in ACAD before importing but our jobs are quite large and this would basically mean keeping a 2nd data set that has to be constantly updated. And batching aside, moving the ACAD projects isn't always 100% successful.

But thanks for thinking of me.

...any news as to whether the forthcoming 64 bit version will use 64 bit words for ordinates?

PostPosted: 16 May 2008, 16:29
by chrisneedham
Yep - sorry, was talking about scripts 'on the back end' in AutoCAD.

Truth is that scripts are only as effective as the consistency is between your drawings. If they've all got their data in the same location, there shouldn't be any reason why you'd have an inconsistency. That's where some creative coding can be great value - in dreaming up the thing that need to be covered. (Aside: I've long believed that the 'CAD idiots' in the office are valuable as tool testers, because their brains don't work in a 'logical' manner, and code is by its nature, logical).

Point taken in that there is extra work required (e.g. potentially two data sets to manage), but to my mind, if there's no alternative, then the next best is "How do we best manage this?". Building simple, robust systems is what I enjoy.

Not sure about any more news on 64 bit Revit, I'm afraid. What do you mean by '64 bit words for ordinates'?

PostPosted: 16 May 2008, 16:34
by David Howe
Please refer to my first entry in this thread for an explanation of 64 bit word accuracy. This is a major problem with Revit as it means users are unable to work directly with ANY MGA based drawings. The upshot of this is that Revit is unsuitable for most government work as MGA is now part of most briefs.

PostPosted: 16 May 2008, 17:01
by chrisneedham
Hi Dave,

I get your point about the accuracy issue, and fully agree, but I meant for my emphasis to be on your word: "Words" - specifically '64-bit words'. I'm not sure what you mean, but it may not matter anyway.

PostPosted: 16 May 2008, 17:09
by David Howe
In computing, a 'word' is a string of bits or bytes treated as a single entity, for example a dimensional ordinate in a CAD program.

PostPosted: 16 May 2008, 17:25
by chrisneedham
Now I get you. I just hadn't heard that expression in that context before. Had you said 'string', I would have been mentally on board a few posts back... :o)

Thanks for the clarification.

Re: Large distances still a problem in Revit 2008

PostPosted: 19 Aug 2009, 12:48
by David Howe
I just received this interesting dialog while trying to import a DWG file. At least in Revit 2010 Autodesk is now acknowledging the limitations of Revit's 32 bit data set. Note that 2 to the power of 32 is 4294967296 - the 2 mile limit to which the message refers.

DWG 2 mile limit.jpg
Revit's 32 bit data structure can't import AutoCAD files more than 4kms across
DWG 2 mile limit.jpg (78.1 KiB) Viewed 10399 times