You may have seen the “extents greater than 20 miles (33km)” warning in Revit before:

Geometry in the file dwg has extents greater than 20 miles (33km). This may reduce reliability and result in undesirable graphic behavior. Click OK to continue, Cancel to exit import.
Extents greater than 20 miles (33km)

I have previously posted about ways to clean up DWG files, best and worst practice, and also how Revit deals with accuracy and precision of big models. The short list of steps to take in AutoCAD to clean up a survey DWG is:

  1. PURGE
  2. SCALE all objects to mm instead of metres
  3. WB – write block to a new file
  4. AUDIT
  5. EXPORTTOAUTOCAD (from a vertical product)

What if, even after all of the usual steps, you still have the ‘extents’ problem? And what if you can’t find the problem in a plan or top view in AutoCAD? That means that you have large Z extents. And you can even have large Z extents from some wayward Text objects with a Z value of like 35000 metres, which will trigger the same message in Revit.

How do we fix these? We need to directly edit the Text Alignment Z in AutoCAD. Here’s how:

  1. Select All Text with Quick Select tool

  2. Then change the ‘Text alignment Z’ value to 0. This also sets the Position Z to zero.

  3. Then either Save As or use the EXPORTTOAUTOCAD command to remove the proxy objects

Now the DWG should Link to Revit without error. Hope this helps some of you 🙂

If you want to Move Text to the Elevation corresponding with the text value, such as for a Civil elevation, you can use this command. With a Civil or other vertical product, start the special command:

  1. _AECCMOVETEXTTOELEVATION
  2. At the ‘Select text objects’ prompt, type All and hit Enter
  3. The text should have been moved automatically

Forum link

Check out the survey results from Design Master Software – interesting that 2/3 using Revit over AutoCAD:

And how does MEP industry take-up of BIM compare with what was expected in 2011?

As with any such survey, its value must be regulated by the question:  
“Do the survey respondents represent an accurate cross-section of the industry itself?”

Read more:
MEP 3D-BIM 2014 Survey Results – Design Master Blog

Video: Matthew Miller recently gave high praise to this class, when he posted that David Baldacchino’s class AB412 Navigating Through the Storm Using Coordinate Systems in Revit “has been the best explanation of shared coordinates, that has helped me understand them.”

Matthew also provides these useful links:
Blogs Talking about Survey point in Revit
Understanding Shared Positioning in Revit

Shared Coordinates

Project Base Point Manipulation

Revit 2013 – Project Points, Survey Points, Revit Coordinates

via

Revittize: Set the Revit Survey Point

When exporting to IFC, you may find that Revit feeds the Survey Coordinates (or shared coordinates) to the resulting IFC file, when in fact you want it to be based on Project Coordinates.

If your project team is using origin-to-origin linking, it will be almost vital that you neutralize the Revit survey coordinates immediately prior to exporting to IFC.

This is quite easy:

  1. Make a new file based on a blank template
  2. Insert a origin locator dwg and draw a couple of model lines over the top (this is purely to give you something to “pick”)
  3. Save and close this blank RVT file (and keep it for future use)
  4. Link it into your live Revit project
  5. Use Acquire Coordinates and select the new, fresh, blank RVT file
  6. Save As this temporary RVT with neutralized survey coordinates to somewhere
  7. Now Export your IFC

Your resulting IFC file won’t be confused about which coordinate system to use – it should now Append to Navisworks and other software using the same origin-to-origin coordinate system as that in the originating Revit project.

In a recent Twitter experiment, I posted three different opinions of BIM and have been monitoring the response through Retweets. Here are the results (as these are embedded tweets, the results will change over time).

The results thus far appear to be overwhelmingly positive – that BIM is indeed “awesome”. I guess the majority of my Twitter followers are, unsurprisingly, supporters of BIM.

I’ll keep this page live as a checkpoint for the statistics – it will be interesting to drop in from time to time and see if the results change as more people from outside my Twitter circle weigh in on this BIM thing…

Interesting – this kind of turns the point cloud technology upside down… It goes something like this:

  • Revit model 
  • to points
  • to site survey hardware (set out the building)
  • build it
  • then laser scan the as constructed
  • compare points of the as built model for quality control
The part I’m trying to get my head around is this – these aren’t really point clouds, but rather, they are setout points of Revit BIM 3D elements for construction use.  Perhaps the word ‘point’ is going to be more popular than the word ‘BIM’ this year 🙂

Learn more / trial at:
Point Layout | Construction Layout Software | Autodesk

You receive a DWG file from a surveyor, and you need to get it into Revit.  You go through all the usual cleanup steps.  You have purged, scaled, done a write-block, audited.  You link the DWG into Revit, create the topo – and it looks like rubbish.

If your survey data has some severe gradient, perhaps relating to a steep retaining wall on the site, you may find that Revit does not model it ‘smoothly’.  Here is an example

The problem is likely related to Revit’s triangulation method for topo surfaces.  You get weird flat surfaces where things should look much smoother and more organic.

Here is a quick workflow that I have used to add some realism to a survey DWG without sacrificing accuracy (note – this method uses AutoCAD Civil3D, you can download a trial):

  1. Open the survey DWG in Civil3D
  2. Create a new Surface (Right click Surface in the Toolspace – Create Surface…)
  3. Add the objects to surface (can be easier to isolate the necessary layers first).  To do this, expand the Surface node, then the Definition node, then select the Drawing Objects entry.  Right-click and choose Add…  You may want to add Contours separately using the Contours node.
  4. Edit Surface Style
  5. Contours – Contour Interval.  Change contour interval to something very small – I find 10mm works well
  6. Turn on the Contour layers for the Surface in: Surface Style, Display.  Also, set a new Layer to be the ‘layer’ for the Surface Contours (major and minor)
  7. Extract the newly created contour objects (select the TIN Surface and click ‘Extract Objects’).  To make my site look better in Revit, I actually had to export the Triangles as well.
  8. Select the extracted Contours / Triangles and save them out to a new DWG file (you can use write-block or the inbuilt Export command in C3D). You will need to take some geometry from the source file (like boundaries) so that you can locate these new contours in your Revit model.  Or keep them in the same file with the new layers you made in step 6.
  9. Import this new ‘high resolution’ contour plan into Revit
  10. Use these contours to make your topography (select only the appropriate layers when using Import Instance while creating Revit toposurface).
Lots of contours here – thanks Civil3D

The result?  Something with a much more ‘organic’ appearance:

Better Revit surface (Realistic View, Edges off, Subregion applied)

Obviously, this method has a couple of caveats:

  • it will take a bit of processing power, both on the Civil3D side and on the Revit side
  • once you have your high resolution data in Revit, it will mean you are dealing with lots (thousands) of points in the topo – you have to decide if the nicer looking surface is ‘worth it’ to you 

Also, using my Quadro FX580, if there were too many points, my computer would basically just hard-crash to a BSOD – save often!  I ended up switching to software emulation (turning off Hardware Acceleration in Revit).

      If you are part of the Revit® Customer Council and you undertook the “annual survey on your Satisfaction with the Revit® Architecture product from Autodesk”, then you probably have received the results via email by now.

      The email explicitly states that I cannot “share, distribute, or blog about any of the information contained in the attached report.”

      So…I won’t.

      However, if you want access to this information in the future, you may want to Join the Revit Customer Council at:
      www.revitcc.com

      Direct link to Join page

      My previous post:
      What Revit Wants: 2011 Revit Architecture Customer Satisfaction (or not)