AutoCAD 2010/2011/2012

AutoCAD 2010/2011/2012

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Registered: ‎05-18-2012
Post 21 of 36

Re: Autocad gives the wrong area for a polyline

05-18-2012 02:02 AM in reply to: whispering

I use CAD 2013 i can not get correct area calculation when more then 2 close poly line opject connect together with touched /over lap path, for example  some columns inside the room, the total area not including column, 

why autocad give up one object / poly line area calculation?

see attached file

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Post 22 of 36

Re: Autocad gives the wrong area for a polyline

05-18-2012 02:18 AM in reply to: leovgi

Hi,

 

interesting situation, but not new!

First: yes I can reproduce your problem in your drawing.

Even when correcting the double vertices and correcting the non-closed polyline to a vertex-cleaned closed one I can reproduce the wrong result in your drawing.

 

And now what's already known with high coordinates: when moving the object close to 0,0,0 the command _AREA works as it should. Anyway, report it to Autodesk!

 

- alfred -

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Alfred NESWADBA
Ingenieur Studio HOLLAUS ... www.hollaus.at
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Post 23 of 36

Re: Autocad gives the wrong area for a polyline

07-11-2012 01:55 PM in reply to: Alfred.NESWADBA

I just found this thread, but wanted to say that I am exepriencing a similar problem. 

http://forums.autodesk.com/t5/AutoCAD-Architecture/Polylines-area-and-errors/td-p/3535038

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Post 24 of 36

Re: Autocad gives the wrong area for a polyline

07-15-2012 11:39 AM in reply to: whispering

So far we have made the following observations on this:

 

  1. The problem appears to have been introduced in AutoCAD 2011, all previous versions appear to calculate the area correctly.
  2. The AREA command can return an invalid number, while the underlying API (Polyline Object .Area Property) returns the correct value.
  3. One situation that seems to cause the problem is when a segment of the polyline follows a return path across a previous portion of the polyline.

In an effort to help AutoCAD users check drawings for cases of incorrect area, we have produced a freeware application that evaluates all polylines in model space and compares the area reported by the AREA command to the area reported by AutoCAD's own API (the Area property).  It can be found in the Free Stuff section of the site below, look for the PAUDIT.ZIP item.

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Post 25 of 36

Re: Autocad gives the wrong area for a polyline

07-16-2012 12:05 PM in reply to: TerryDotson

Can someone let me know specifically where this error can show up?  I'm using 2011, and definitely need to know that my areas are right!  None of our drawings are near the origin, everything is kept in 'World' coordinates approx 5,000 km away from the origin.  (That's 3,000 miles for all you Americans  :smileytongue: )

 

Here's what I'm wondering: does the error only occur when using the AREA command?  Or does it effect anything else?

 

Terry Dotson said "the underlying API (Polyline Object .Area Property) returns the correct value."  Is that the value I see when I look in the properties box?

Can anyone else confirm that the area given in the properties box is always correct?


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Post 26 of 36

Re: Autocad gives the wrong area for a polyline

07-16-2012 12:15 PM in reply to: troma

While AutoCAD capabilities have been known to deteriorate in large coordinates (trim command comes to mind) this problem is not limited to large coordinates.  Attached is a small drawing (based on joemcd's image example) that has a limits of (0,0) - (100,100) and it reports a bad area in 2013 using the area command.  The area doesn't show in properties, I suppose it considers it a self-intersecting polyline.

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Post 27 of 36

Re: Autocad gives the wrong area for a polyline

07-16-2012 01:44 PM in reply to: TerryDotson

I see you said that this drawing gave the wrong answer in 2013, and I'm still in 2011.  Someone else said that the problem started in 2011, and got me worried.  Looks like this problem is rather random in its attacks.  I downloaded and opened up that drawing you posted.  Here's what I got (C3D 2011):

 

polyarea-command.PNG

 

polyarea-properties.PNG


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Post 28 of 36

Re: Autocad gives the wrong area for a polyline

07-16-2012 04:30 PM in reply to: troma

Try the TEST.DWG posted by "whispering" on the first page of this thread in 2011.

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Post 29 of 36

Re: Autocad gives the wrong area for a polyline

07-16-2012 04:54 PM in reply to: whispering
Try it only in 2013 don't in 2011
Mistake reasult only in 2013,
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Post 30 of 36

Re: Autocad gives the wrong area for a polyline

07-17-2012 02:36 PM in reply to: TerryDotson

Again, working in C3D 2011

 

polyarea-wrong..PNG

 

So yes, I'm getting the same result as posted by Whispering.

 

I double checked by exploding, deleting the joins, and converting back to polylines individually, entering into a spreadsheet to subtract the small areas from the outer.  I get 294155228 that way.

 

Very concerning generally.  Fortunately I rarely have to work with areas like this (with internal parts subtracted), but it's a scary thought!


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