BUG! Can't rotate project north a very small amount

[Wes Macaulay]

We've just discovered a glaring problem in Revit: you can't rotate project north by a small amount -- say 0.1°.

Try this: create a host project for a linked file. Link in a Revit file -- rotate it 0.1° in either direction, publish coordinates, save file, close.

Open the project file and switch the view to True north. Nothing happens -- there is no rotation. At least not here, using the 0810 build of RAC.

[dgraue]

There are definitely small tolerance issues with Revit. An issue we repeatedly have is importing a civil engineer's site plan drawn in Autocad. Property lines are rarely at 90 degrees to one another and many instances are just a few tenths of a degree out of square. Revit is not able to maintain the exact property line configuration of the imported dwg. It is ever so slightly off but that translates into an error of several inches over a 300' length of the site!

[dbaldacchino]

I've observed the same issue with families since 9.1. Revit just doesn't like small angles (or dimensions for that matter). I have a line-based family that figures out a radial array based on length of arc and the distance between the chord and the peak of the arc....the math works prefectly, but for a very flat arch, the resulting angles are too small and Revit doesn't know how to represent that (family breaks...doesn't display right). No matter what you set in the project units/settings, the problem still persists.

[Calvn_Swing]

Or the whole issue with "line is slightly off axis" errors. Don't get me wrong, in some places I think that is useful information (grids, sketches) but sometimes that slightly off axis is correct. I've got one project with a good 200 +errors of that type where those lines are correct. I can't change them, and I can't get rid of the bloody errors! Why can't I "accept" the error and tell Revit it's OK!

[mruehr]

Or the whole issue with "line is slightly off axis" errors. Don't get me wrong, in some places I think that is useful information (grids, sketches) but sometimes that slightly off axis is correct. I've got one project with a good 200 +errors of that type where those lines are correct. I can't change them, and I can't get rid of the bloody errors! Why can't I "accept" the error and tell Revit it's OK!

I would like a password protected Ignore and Accept Command so the cad manager can say OK

[DaveP]

I've got a couple of projects with a pile of "Slightly off" lines, too.
My first suggestion is that they change the error message to read:

This Line was drawn in AutoCAD

If they can't do that, I'd at least like to eliminate that error for Detail Lines. I can see its' usefulness for Walls and Room Sep. lines, but, frankly, who cares if a Detail Line is crooked?
A crooked Wall may affect other elements or cause inaccuracies, but a line in a Detail View affects nothing else & should not be reported as an error.

[dbaldacchino]

Wes, see if this works....

Rotate the project the opposite direction by, say, 10 degrees. Then rotate again in the other direction by 10.1 degrees (or whatever that decimal figure is)....see if Revit accepts that.

[Dimitri Harvalias]

I tried that the other day David... no go.

[dbaldacchino]

Thanks Dimitri. That's intresting...I just tried it myself and the walls do look jagged, which means they are rotated. I rotated the project by 40.001 degrees and the dimension does read that.

The problem I'm seeing is that when you rotate the project by a minute amount that puts the project almost parallel to the orthographic axes, Revit cannot snap perfectly horizontal or vertical anymore (in a view set to True North). So when you place a line thinking it is perfectly horizontal, it's not; it's actually parallel/perpendicular to what you've just rotated. To confirm this, I exported the view to dwg (by shared coordinates) and mesured the angle in ACA and the building did rotate by 0.001 degrees. See attached snapshot. So it does seem to work.

[Wes Macaulay]

Right you are David -- in some case it does work, but when you're rotating true north just a hair off project north, you don't get the proper display of linked objects. You can rotate true north on its own by 0.1° and it works, but the it messes up the way you note. Plus the linking + rotating method should work, which it does not.

[dbaldacchino]

I see your point, which I also came across in my little experiment (lines not snapping to horizontal anymore). Here's another interesting fact....I turned on the workplane grid and rotated it by 0.1 degrees, which is the rotation I used in this experiment. Now I can draw perfectly horizontal lines by snapping to the grid, but I get the "line slightly off axis" error! Anyway, i guess you could use the workplane grid to overcome some issues, but it's definately something that needs fixed. Thanks for bringing this up. In the meantime I'll keep doing sites in Autocad and if the rotation is small, I won't even bother ;)

[jabamax]

Guys,
Still seem to have this problem in 2014. Has anyone got a work around?
Thanks

[dbaldacchino]

To my knowledge, nothing has changed. Just did a quick test and rotated True North via the Project Base Point gizmo and it accepts the rotation of .01 degrees, but then still loses the ability to draw perfectly horizontal lines in a view set to True North. I exported the view to DWG and then drew a horizontal line in AutoCAD, but it was perfectly parallel to the exported geometry. So then I set the Angle to True North to 20.01 and exported and this time, the geometry is indeed rotated by that exact amount. So if in Revit you have such small rotations, you need to always use a large rotation angle (ex: 10 plus the small angle), then re-rotate back by that same amount (10 in this example) to get the true rotation of the geometry in your exports. Sucks, but that's how it is....good thing is we know about it at least.

[mike.154133]

Now 2018 and still have the same problems. Trying to rotate the Project North / True North where there is a difference of only 0.18979 degrees. Can get the project to be orthogonal BUT then when placing a Reference Plane it is not orthogonal, having a slight angle. So I can get either to project OR the drawing to be orthogonal but NOT BOTH?