Selection sets to extract changes made to drawing

Is there was a way when a drawing has changed to create a backup of just the changed entities?
Can comparing selection sets be used to determine what has changed or been deleted or added in a drawing since it has been opened to enable these changed items to be wblocked out?

I have had a brief try with the CompareDWG ARX program which does appear very good however from what I have seen of the evaluation copy, It can save changed drawing entities to a separate file but it modifies block names, layer names and colours. Therefore "corrupting" our drawings because they no longer match our CAD Standards.

 

Paul,
Our in house drawings are broken out with base drawings in a dwg folder and sheet drawings in a prod folder. Since out designers are not supposed to plot drawings to be sent out of the office, I redefined their text edit commands to use a routine that attaches xdata to all text modified by designers if they are in the production folder. This gives the cadd department the ability to run a second routine to change color and layer of all modified text. This was done to let cadd dept. know if things had been changed so they could be checked for standard formatting. I then wrote a routine to strip xdata from all text, which then has to be set back to std layers.

All this being said, it is very possible to do what you are asking, although a selection set might not be the best way.
You could set something up similar to what I have and then isolate changed layer and wblock out.
This wouldn't help you find out what had been deleted.

Hope this helps!
Rob

 

You could try something like this. The only problem I see right now is when you have new objects drawn in different spaces. Maybe you can do a saveas, then erase all the objects but the ones in "GlbNewObjectsSelectionSet" because those are all the new objects.

(defun JustOpened ()
; Set so it works on all opend drwings
(setq GlbOpenedSelectionSet (ssget "x"))
)

(defun c:GetAddedObjects (/ cnt1 tmpEnt)
; Run when you want to block out.
; Wblock out the selection set "GlbNewObjectsSelectionSet"

(setq GlbNewObjectsSelectionSet (ssget "x"))
(setq GlbErasedSelectionSet (ssadd))
(setq cnt1 0)
(while (setq tmpEnt (ssname GlbOpenedSelectionSet cnt1))
(if (not (ssmemb tmpEnt GlbNewObjectsSelectionSet))
(ssadd tmpEnt GlbErasedSelectionSet)
)
(vl-catch-all-apply 'ssdel (list tmpEnt GlbNewObjectsSelectionSet))
(setq cnt1 (1+ cnt1))
)
)

Tim

 

Rob,
Thankyou for sharing your method of tracking changes. That appears to be a very ingenious method. I will have to look into the customizing possabilities of attaching xdata.

I have also receieved some feedback from the developers of CompareDWG following a query that I sent them.

I have briefly tried your ComapareDWG program overnight. It is very good. With the drawings it produces that show what has been changed they use modified blocks to represent colours as per your legend. Please could you tell me if the full version modifies layer names, block names and colours or if it can use the native layer and block names?

They replied:

Dear Paul,

The trial version and the full version of CompareDWG are exactly the same as for functionality, so what you see in the trial is also what you get with the full software.

You are right that layer names etc are renamed because CompareDWG uses xrefs to display the results. However, if you prefer files with unchanged properties, then these are also available. When CompareDWG checks the drawings, ti first saves the results into Temporary Drawings (see Help file chapter Technical Backgrounds / The Temporary drawings). These are regular drawings with the original properties that you can use as regular AutoCAD drawings (please note they may be deleted as temp files, check the option in CompareDwg options). I think this may be what you need.

I am looking forwaard to trying the various options to suit our needs.

Cheers

Paul

 

Thanks Tim, I am wrapped that you have taken the time to develop a routine to suit this problem.
I will have a go at using your routine and let you know how it went.

Thanks again.

Paul