20 Mile Threshold on Import

This is a follow up to my earlier post this week regarding the 20 mile threshold. A comment to that post mentioned that the governing extent is equivalent to a 10 mile radius sphere whose origin is at 0,0,0. In my own testing I've observed the threshold is more closely defined as a cube.

This image is a 10 mile radius sphere with a line segment that travels beyond the edges of the sphere but within the boundary that a cube would have.

You can see the highlighted square is the extent of the DWG file and line extends outside of the sphere at each end but is still inside the boundary of where a cube would lie instead.

This image is the same file but the line is altered to extend beyond the edge of the sphere/cube extent.

This is the message that appears when I reloaded the file after altering the line's extent.

The warning can be avoided if we ensure that the DWG file doesn't have any elements that extend beyond the 20 mile cube (10 mile radius). The cube can be quite far from the origin of the DWG file but nothing can be outside the cube's boundary.

Transparent Elevations and Large Coordinates

Back in December 2011 The Revit Clinic shared a post called Interior Elevations and Large Coordinates in the Project. It's worth echoing it again four years later.

It boils down to this. If you link a DWG file that has geometry that extends beyond Revit's 20 mile threshold then you may find elevation views (or section views) look transparent. In 2016 I find that some views just stop responding to Visual/Graphic Style settings at all. If you remove the offending file the problem goes with it.

It is necessary to clean up and reduce the size of the offending file so that the threshold is not crossed. I shared this list in the past, in particular consider using the WBLOCK technique.

• Import multiple Survey files individually (don't nest them as xref's)
• Purge everything you don't need, purge again
• Use Wblock if you can't get Zoom Extents to focus on just the relevant portion of the site
• Remove Named UCS (Revit only wants the World Coordinate System)
• Set UCS (User Coordinate System) to WCS and Plan to WCS
• If the survey isn't oriented to WCS, North is "up", have the civil engineer/surveyor change their file first
• Identify a specific location within the relevant part of the survey, put a marker, identify its coordinates, better still make those coordinates easy to use, even clean numbers.
• Make sure everything actually aligns correctly in AutoCAD first, no point setting it up in Revit if it doesn't work there
• Once you get a working first survey file, pass it back to the surveyor so they know what you need in the future

That might be a lot of work...so fortunately there IS an easier fix. Just make sure the offending DWG file is NOT visible via Visibility/Graphics in views that are acting up. It should restore normal behavior.

I prefer elevations that aren't see thru. Watch out for those surveys folks.

Revit and the 2 Mile Limit

I’ve read a few posts on this subject in the last few months, a couple more recently offering a way to get around the issue. I echoed a post at the Revit Clinic blog a few months ago too. Paying homage to “The Princess Bride” movie I dubbed the files affected by this issue “Files of Unusual Size” or FOUS, like the “Rodents of Unusual Size”, ROUS.

Revit examines the cad file you want to import and determines how “big” the data is. If it finds that all the data in the file results in data greater than two miles across, either horizontally or vertically it will generate the error message. It is not just that survey data is a great distance from the origin in the file. The survey itself might be fine but there is some geometry lurking a great distance from the important stuff that creates the condition that Revit is hoping to avoid.

You can test this out yourself. Create a little survey of lines and then park a line more than two miles away from those lines. It could be as simple as two lines very far apart. Import the file and Revit complains.

There are a few ways to resolve this. You can fix the file or just fool Revit into accepting the large data despite its best effort to do otherwise. The correct way should be the solution that is the least work and hopefully doesn’t put you at risk for altering the civil file in a way that leaves room for error.

To fix the file you can refer to the earlier post here or to the one at The Revit Clinic. If you are interested in fooling Revit and doing “nothing” to the file then consider this post.

Another solution that I’ve used several times is to create a new empty cad file (container file) and then create a new external reference with the FOUS in this new container file. Use the same 0,0,0 world coordinate location and make sure the external reference is attached. Now import this container file with its attached external reference, no warning message, the size of the FOUS is “hidden” by the container. Happy Imports!