dwg export scale problem

[info1898]

Why is it that when exporting to AutoCad scale is messed up? I need to reset of all dimensions, linetype scales, viewport layouts, etc for every file to make it work and it is a real pain. Is there something I am missing? The file seems to be multiplied by 10 !!!! Can't you set the export scale units like you do with imports?

[Dimitri Harvalias]

When exporting from Revit the scale is always 1:1. You might want to check the AutoCAD file you are importing into. Be sure the drawing units are the same as they were in the Revit file e.g. mm to mm or decimal feet to decimal feet.

[info1898]

Is there a way to specify a default autocad file to export into? Then I can do all setup in the autocad file so the revit file imports correctly. Is it only me, but the if the imported dimension text reds 500 cm, the tape measure is 5000. When I change the units, the whole drawing becomes 1/10 smaller, and I need to do rescale of all text, linetypes and dimension styles. This is really frustrating with tens of drawings to be exported. I would appreciate any help.

[Steve_Stafford]

What are you exporting? A view, a sheet with views?

What are your Revit units? Millimeter or Meter for example

When I export a view I get 1:1 geometry with dimensions and text at the size required for the scale of the view. You should see this as well.

When I export a sheet with views...I get individual files...you get a sheet file with paper space viewports of model space based external references of the views...again the geometry is correct, similar for text but it is based on the drawing scale of the Revit view.

I didn't have to make any changes to the dwg file to get these results.

What version are you using and is it an international (language specific version)?

[info1898]

I was using revit 5 but I had the same results in revit 6.1. I export sheets and I understand how it transtlates into xref. I use centimeters with a 1:100 scale. The exported drawing looks ok and the dimension strings have the right distances written but when I measure the distance in acad it is multiplied by 10. If I do update dimensions they read the real value (150 becomes 1500). I attach an acad file exported from revit that shows this. I appreciate any help.

[info1898]

It seems we cannot attach acad files. I hope you don't mind if I email the file directly to you Steve.
Thanks for your help

[Scott D Davis]

ZIP the file and then attach it. It should work!

[Steve_Stafford]

I took a look at your files.

I find the output is accurate 1:1 between Revit and Autocad, 200mm is 200mm. That's good!

There does seem to be an inability to export a sheet with views and honor the "ltscale" that the viewports would need to show linetypes correctly. I don't recall this always being a problem, but then you said it was doing it in 5.0 too? When you export a view only the linetype representation does work and this is the more common export exercise I do. I seldom have needed to export an entire sheet for others to work on, usually just the model space data.

If that is your need then perhaps since you know that viewports aren't adjusted for proper linetype display, maybe it would be worth it to set up a routine (lisp) to make it easier to fix once in Autocad. I'd also talk with Revit support to log the issue if it isn't behaving as intended by the developers (my guess is it isn't).

Regarding dimensions, Revit does seem to create an inaccessible dimension style that lies somewhere in between the Autocad standard style and the one Revit adds to the dwg file based on the Revit dimension style. Yet assigning a dimension to this available style produces different results. It isn't surprising that the font doesn't hold since the Autocad file would need to have the same font style available, though perhaps Revit could create it?

As a workaround, if you use match properties in Autocad you can quickly apply your office standard dimension style to these dimension so they conduct themselves as you see fit.

Hopefully we'll see some more control over how the data is exported in the future, sorry I couldn't be of more help.

[info1898]

Thanks for your efforts Steve. 200mm is 200mm is right, the problem is that I am exporting in cm, and the acad file is in cm, so the file is not to scale. Also, the dimension text reads 20, while it is in reality 200. I am a new comer to revit and I wonder how this hasn't been dealt with much earlier. Most clients demand an acad soft copy of the projects, so we need to do the all the fixings for acad files, and this is really time consuming. I would have thought that the exported file should have exported also dimension styles, linetype, scales etc, that the acad file is a copy image of the original revit file. I really hope this will be dealt with seriously in a future release.

[Scott D Davis]

I'm thinking the scale is right, but just your units in the autocad file are set to mm instead of cm. if its exporting 1:1, and 200mm is revit is still 200mm in autocad, then everything is correct. You just need to change the units in autocad to cm, and this will update the dims from 200mm to 20cm.

[Steve_Stafford]

Autocad has no understanding of cm versus mm. In fact Autocad is unit ambivalent. You can draw a unit and call it a parsec and I can draw a unit and call it a furlong. Both drawings are drawn 1 unit of length the difference is what we intend, Autocad can't care less.

The file Revit exports is accurate...20 cm is 200mm. The "inaccuracy" you describe is perception, your notion that a base unit is a cm. We draw using mm as the base unit, does that mean we're wrong or you are?

Dimension style settings distinguish a unit of measure. In Autocad you can draw (4) one unit lines and apply four different dimension styles using different scale values and report distinctly different lengths. Whereas in Revit you can only report the same length in different formats, always the same equivalent length.

Here in the States surveys and civil drawings typically arrive at our office using 1 foot as the base unit whereas the architectural drawings we prepare use 1 inch as the base unit. Both drawings are correct, you must adjust them for the unit "language" you speak.

Revit does understand the differences between units so you can work on a project in Revit using imperial and arbitrarily switch to metric and you don't have to scale your drawing up like you would in Autocad.

Since your office uses a base unit of cm you will have to scale the export of Revit documents for the same reason we have to scale a civil plan. Because you are altering "reality" in a sense. Revit's assumption of 1:1 is the base unit of inch or millimeter and your office uses a base unit 10 times larger. When you choose cm in Revit, you have not changed the base unit, just the display of values as you draft.

The unit issue is fine with me the way Revit handles it. I'm concerned about the ltscale and representation of the graphics issues you raised. The viewports Revit creates in a dwg export should display linetypes correctly. It should be reasonable to expect dimension styles could be faithfully recreated too.

[info1898]

I understand this might be an acad problem. We always faced difficulties with scale plotting, ltscale, text & dimension scale etc.. but with a drawing template we can arrive at a workable settup. Since acad remains the dominant cad software, I think revit has to deal with export issues in the same way it deals with importing files into revit. I don't have any problems importing> I can specify the units and the acad drawing is imported correctly. If we can specify the exported unit, and an acad template file to export into, I think that will solve the problem.

[stuthill1106]

Is there a way to set Revit so that it exports to a 1/4"=1' 0" dwg so that I don't have to change the scale in AutoCAD? I wouldn't care if it was just for one floor, but I'm exporting 14 floors, 2D and 3D, Architectural and Structural, and it would save me some steps if I could set the scale to suit our standards (1/4")