BILT

BILT
Speaker

Tuesday, 3 April 2018

Accurately Rotate a Section in Revit

When you have a non-orthogonal building model in Revit, you often need to create sections (or elevations) at various angles other than orthogonal.  Normally you would want sections to be perpendicular/parallel to the angled model elements - the image above shows a section somewhat off parallel (much exaggerated version of a typical example where it may be slightly off).

If the section is not exactly perpendicular (or parallel) to objects in the model you can encounter some very frustrating problems:
  • You may not be able to dimension sectioned elements
  • 2D Symbolic lines in families may not show up (eg. door swing in elevation)
If you try to rotate the section to make it exactly perpendicular (or parallel) to objects in the model, it is not as easy as you might expect:
  • One thing to avoid is measuring an angle and then typing in the measured angle during the rotate process - it is never accurate enough, even if you use several decimal points.  Revit is extremely fussy about this - even a difference in angle of 0.000001 degrees may be enough to play havoc with dimensions and symbolic lines.
  • It is much more accurate to rotate by snapping start and end rotation points to the section to be rotated and some other reference element.  The other problem you will encounter is an inability to snap to section lines.

Workaround

The trick here is two preparatory steps
  • Create a reference plane snapped to the section tail end, and exactly parallel to the angled wall
  • temporarily turn off the section markers at the ends of the section line - use the little cycle symbols et each end of the section.  Then you can accurately snap to the section line when rotating. 

 

To rotate the section:
  • During the rotate command, snap the centre of rotation to the point where the reference plane and section tail end meet (they must meet exactly)
  • Snap the start of the rotation to the section head end
  • Snap the end of the rotation to the other end of the reference plane


The section should end up exactly perpendicular (or parallel) to objects in the model.  Unfortunately the annotation on the section will have moved (much exaggerated in this example), so you may need to do some tidy up, and replacement of dimensions.
  • Don't forget to turn the section head/tail marker back on.

You should now be able to dimension to sectioned elements, and the 2D symbolic lines in families should now be visible.

It is your call as to whether it is worth rotating the section line or just create a new section - it all depends on how much annotation there is, and how often the section has been referenced in other views.

Once you have the section oriented exactly right, you surely don't want to lose it, so most likely you will pin it in place.  Revit is very annoying in that you cannot change the 2D extents of a pinned section (as you can with datums like grids).  Wouldn't it be nice to be able to pin a rotated section and have it never move again, but still be able to adjust its 2D extents per view, without unpinning it.  If you would like that, please go to the Revit Ideas forum and vote for 'Allow us to change 2D extents of pinned sections'


[Edit:  Now we have a new way to do this in Revit 2019.1, which has an 'Align Section' functionality, using the existing 'Align' command. ]

3 comments:

  1. Instead of turning the section head off, see if hovering over the point where the line meets the head and tabbing. It has worked really well for me. Also, I use the element itself to align the section with by moving either the tail or head point to the object and rotating from that point (using the other end point of the section line as the second point that will be brought parallel). This way I don't have to manage any additional references, and it is done graphically.

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  2. Thanks for your comments David - the Tab key is very underused in Revit, and is extremely useful in situations like this. I like to be able to snap directly to the section line to avoid mistakes; I like to keep the section roughly in its original location so its annotations don't move so much - hence the reference plane.

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  3. The factory just marked the "align sections" as accepted so hopefully this will get a LOT easier soon :)

    https://forums.autodesk.com/t5/revit-ideas/align-sections/idc-p/7904721#M19485

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