AutoCAD

Bug Watch: Use AutoCAD 2007? 3D? Read On

7 Aug, 2006 By: Steve Johnson

Unhelpful Help, a pair of potentially important 3D tips and how to bring back Copy and Paste in older releases.


Not Very Helpful (2004 to 2007)
Here are two bugs for the price of one. Before you can see either bug, you must have a floating command line, so grab it and drag it somewhere. First, invoke a command, such as the Line command. While the command is active, press F1 for Help. The Help window appears as expected. Leave Help open and return to AutoCAD. Now press F1 again, because this bug only occurs when Help has already been invoked. You probably will see a dialog box such as this:

figure

It's lying, of course. The Help file is perfectly fine. This bug is more of a nuisance than anything else, because the superfluous message doesn't stop Help from working. Just select OK and carry on. This is not the case with the second bug. If you redefine your F1 key, the above message appears every time you press F1, and the macro you have assigned to the F1 key won't work.

Workaround: None known other than docking the command line.

Extremely Inexact Extrusions (2007)
The Extrude command lets you specify a cross-section and extrude it along a path. Before 2007, this worked very nicely and could be used for things like road design. In 2007, it can produce very inaccurate results. To see this in action, open the drawing EXTRUSIONBUG.DWG (contained in this Zip archive) in AutoCAD 2007. Use the Extrude command, pick one of the trapezoids on the right, use the Path option and select the yellow 3D polyline as the path. Repeat for the other trapezoid. You would expect the resultant extrusions to match up, but they are a long way from doing so. They match up perfectly in AutoCAD 2005 and 2006.

The extrusion, rather than following the specified path, follows whatever path it feels like following. The extrusion can weave in and out of the specified path and shoot past its end. If you're lucky, the mistake will be obviously incorrect and you can fix it right away. If you have a more subtle problem and you don't notice it, your road design could end up requiring moving a lot of dirt, for a pretty penny.

Workaround: Use the Sweep command instead. You might need to turn off Alignment and specify a base point every time you use the command, but the results will be just as accurate as the pre-2007 Extrude command.

Upgrade Your Driver, Downgrade Your Performance (2007)
With Autodesk promoting the 3D capabilities of AutoCAD 2007, it's a shame that the 3D performance of 2007 appears to be a step down from earlier releases, even when not using the fancy new visualization features. Complex models seem to use far more RAM than before, so be prepared to throw some hardware at 2007 to make it live up to its 3D promise.

Part of the hardware you may need to consider updating is your graphics card. Autodesk maintains a list of supported cards and drivers, so check that out before buying anything.

Be aware that AutoCAD only makes the most of a graphics card if it knows that the graphics card and driver combination will work properly. If you buy a graphics card, the supplied driver may be earlier than the exact version that AutoCAD fully supports. If you download and install the latest driver, it may be later than the exact version that AutoCAD fully supports. The driver may work fine, but AutoCAD assumes that it doesn't, just to be on the safe side. The upshot is that your new purchase and conscientious updating of your graphics driver can leave you with a system that doesn't perform very well.

Workaround: Make sure you check Autodesk's Certified Hardware XML Database, which may have been updated to include your card and driver combination. Failing that, use AutoCAD's 3dconfig command and check to see if hardware acceleration is turned on. If it's not, and you think it should be, turn it on. You may see a dramatic difference in performance. You may also start to see stability problems, so be prepared to turn it off again if that happens.

Falling Over Backwards Again (2007 and DWG TrueConvert affecting R14 to 2002)
In May I mentioned that drawings saved by the vertical AutoCAD 2007 variants caused crashes with earlier releases. In June I mentioned the problems when copying and pasting between different releases on the same system. Now here's a bug that sounds a bit like both of those, but is actually a third problem.

If you use AutoCAD 2007 and save a drawing down to Release 14 or AutoCAD 2000 format, this appears to work fine. You can give that drawing to another person using Release 14, AutoCAD 2000, 2000i or 2002, and they will be able to open and work on it without problems. That is, until they try to Copy and Paste from that drawing. Copy works correctly but the Paste does nothing. There is a similar problem with Wblock and Insert, because Copy and Paste are just a front for Wblock and Insert anyway.

Workaround: Inserting the problem drawing into a new drawing seems to strip out the problem. This method is more awkward with paper space drawings, of course.

Fix: Autodesk has released a fix for this problem. Once you have copied the new ACDB17.DLL file over the original AutoCAD 2007 one, it no longer creates drawings with the problem. It also cleans up existing drawings. Just open and resave them in the required format with a fixed AutoCAD 2007.

If you're a user of AutoCAD 2002 or earlier struggling with this problem, you can still fix up the drawings even though you don't have AutoCAD 2007. Use the free utility DWG TrueConvert instead. Just make sure you apply the fix to DWG TrueConvert first, otherwise you'll just create more drawings with the same problem!

What if you have a huge number of drawing files and you don't know which ones potentially need fixing? On the same hotfix page, you will find a small utility that detects those drawings that have been saved by AutoCAD 2007 down to to Release 14 or AutoCAD 2000 format. Once I pointed out the need for such a utility, Misha from Autodesk went out of his way to make sure it was quickly developed and made available. It is heartening to see that beneath Autodesk's sometimes impersonal corporate image, there are individuals who really care about the needs of users at a detailed level.


AutoCAD Tips!

Lynn Allen

Autodesk Technical Evangelist Lynn Allen guides you through a different AutoCAD feature in every edition of her popular "Circles and Lines" tutorial series. For even more AutoCAD how-to, check out Lynn's quick tips in the Cadalyst Video Gallery. Subscribe to Cadalyst's free Tips & Tools Weekly e-newsletter and we'll notify you every time a new video tip is published. All exclusively from Cadalyst!
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