Autocad Survey Files = Visibility Problems

[hworrell]

I have recently encountered a couple revit files with autocad surveys loaded into them. (Yes, I've told my users not to do this. Yes, I've told my users to clean any files before inserting them into Revit. Yes, I've told my users that even if they do that to put the survey file on a workset that is off by default in all views)

Both the files had some strange visibility issues occuring - one project in a finish plan, none of the walls were showing up (they could be selected, but were not visible). The moment I hid the survey file, all the walls appeared as they should.

The same thing happened in a different project - except it was for mullions... only the mullions wouldn't appear, again - they were selectable, but not visible. Panels were visible. Hid the survey file and then they appeared.

Just wondering if anyone else has run into this... And if it is only survey related (large files, 3D lines, etc)

I am thinking of a new policy..not allowing users to insert survey files directly into the project...

-Heather-

[Revitaoist]

I get a lot of surveys with a bunch of 3D information in them, and this may be the problem you are experiencing. I've had many problems with referenced CAD files including lost references, material editor crashes, etc. My latest trick for handling this went:

1. 'Flatten' and 'overkill' the CAD file
2. Insert CAD file into a generic model family
3. Explode and convert all lines to a Revit line type
4. Copyclip all revit lines into a NEW generic model family

Now there is absolutely no CAD information in there, and if that bugger gives you any problems delete it in your project browser.

[MikeJarosz]

'Flatten' and 'overkill' the CAD file


Remember that flatten will increase the size of the file dramatically. Here is one reason why: every block is made to be unique. If you have 50 doors made from one block definition, flatten creates unique definition door1, door2, door3 etc. You would probably be better off exploding the blocks than allowing flatten to process them. Even then, you may have some leftover 3D artifacts.

It's been a while since I've used Acad (this is a Revit site, after all) but I recall that over the many years I used Acad I was never impressed by the performance of flatten. Part of the problem is that Acad does not use cartesan geometry for z coordinates. The z coordinate is a vector, which brings vector math into the picture. To manipulate the z coordinate each object has to be translated to be normal to the view then translated back to the UCS.

If it sounds messy, it is. I wrote a VBA program once that manipulated polygons. I had to buy a textbook on vector geometry before I could understand what Autodesk had created. AUGI helped a lot too. There's an AUGI guy in New Zealand who understood Acad polygons totally who showed me the translation routine. The flatten writers must have faced similar difficulties. (Unless they were math PHDs, which Autodesk can afford to have around.)

[Revitaoist]

You are absolutely right, Mike, and to be correct I do not use the command flatten or flatshot, as they also create very minor inaccuracies (at /256"). The proper order of commands in AutoCAD is

1. Explode everything
2. Select all lines and adjust their Z-Axis to zero in the properties
3. Switch to a front or side view to double check nothing is over or under zero.
4. Run 'setbylayer'
4. Run 'overkill'

[MikeJarosz]

Not to beat a dead horse, but for the benefit of Revit users who might not know, overkill has problems too. I never use overkill on the entire file first, especially a total file explosion. I select sections to clean one at a time. Remember to save between sections. After the file has been cleaned in sections, I clean the whole.

Overkill has a tendency to freeze on large files. I mean the BIG freeze. The big red button freeze. It disassembles polygons looking for null or colinear polygon sides. It doesn't do them one at a time. It dismantles them all, then puts them all back together again. If you freeze while the polygons are dismantled, you are in deep trouble.

Of course, that is exactly what happens.

I recall seeing overkill in the Acad installation folder somewhere. It was a LISP routine. I'm suprised after all these years that someone hasn't taken it apart and improved it.