I heard a lot of questions being asked today during the webcast about file format.Â My information here may not be written in “Official” terminology, but it will explain what kind of behavior you can expect from opening drawings back and forth between 2007 and 2008.
FROM AN AUTOCAD PERSPECTIVE
AutoCAD 2004,2005, and 2006 had the same drawing format- the 2004 dwg.Â This meant that if you had any of these three releases you could open drawings created in any of the other releases.
AutoCAD 2007 brought with it a new file format- the 2007 dwg.Â You could open 2004 format (and below) in AutoCAD 2007, but 2007 dwgs could not be opened in anything but 2007.
AutoCAD 2008 also works with the 2007 dwg format.Â So if you work with people who use 2007, you will be able to share drawings back and forth with no necessary conversion.
FROM A CIVIL 3D PERSPECTIVE
Civil 3D is built on AutoCAD.Â So all of the above information applies to the AutoCAD objects you create in Civil 3D.Â Such as: lines, arcs, circles, dtext, vports, dimensions, etc. etc. etc.Â This means that if all I ever did in Civil 3D was “draw” using AutoCAD tools, I could share drawings between 2008 and 2007 with no problem.
However, the Civil 3D objects don’t follow these rules.Â Every release, Civil 3D objects become smarter, faster and more powerful.Â So from a Civil 3D object perspective, each release is a whole new “format”.
What this means in practice is that…
You can open a Civil 3D 2007 (or lower) drawing in Civil 3D 2008 and it will bring all of your old objects forward and they should (should) be OK.Â There are some things you’ll want to do (like convert your subassemblies to .NET and do an audit, etc) but for the most part I haven’t seen anything fundamentally messed up. (I make no guarantees, however.)
You can open a Civil 3D 2008 drawing in Civil 3D 2007 but any Civil 3D objects are absolutley unusable, and probably unviewable, too.Â Most often they show up as big rectangles.
If you have a drawing in Civil 3D 2008 that you need someone using an AutoCAD 2007 or lower based program to be able to see, you must either explode everything and save, or do a File>Export to AutoCAD (2007, 2004, etc).
The moral of the story:
If you want Civil 3D 2008 objects to remain intellegent and useable, they must remain in Civil 3D 2008.Â Going backwards in any form will make them “dead”.