topic Re: Need API Of DWG Compare App and for Tracking Drawing Changes in .NET Forum

Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Fri, 30 Sep 2016 13:41:14 GMT

Hi,

I am developing a .net application for auto cad in that i want the functionality like compare two drawings and keep track of drawing changes which can be accept, reject. So is their any api's available for that or is their any other way through which i can achieve this functionality. Please let me know if possible by any way.

Many thanks in Advance.

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Fri, 30 Sep 2016 14:12:24 GMT

Would be a nice request for a new standard feature... I mean some sort of Journaled DWG file format...

If I had to do this I'd implement a journal feature, attaching event handlers to Database objects Added, Modified or Deleted, and recording handles of corresponding objects, maybe marking the journal also with revision and publishing events.

This way you may quickly list changes between any released version, but you still need to keep previous versions as separate drawings, since you may want to retrieve deleted or modified objects from previous versions and check/show real differences.

Journal may be an advantage, but missing that nobody prevent you to check differences between each objects using handles (supposing you have an original file and a revision of it), but it'd require a lot of machine power to check each entity for actual changes (while it would be easy to check added or deleted objects...).

It may be easier attaching a TIMESTAMP value on each modified entity, maybe you can use XDATA to attach such value and quickly check for modified entities... still lengthy on large drawing, but manageable.

Just a few ideas... but I'm really interested since I've developed a document management application for DWG and this feature (quickly check changes between revisions) would be much appreciated!

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Sat, 01 Oct 2016 06:14:05 GMT

Thank you for your reply,

As per my understanding you are trying to say that we have to maintain original and new version of the file as well as we have to keep record into database when objects or entities are created, modified or deleted in respective events, so that we can compare them.

Please correct me if I am wrong, because I am unable to understand that from where I have to start.

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Sat, 01 Oct 2016 07:08:16 GMT

Yes, you understood correctly my point of view...

Let me elaborate, maybe we can get to new solutions...

I assume here we start from a version of a drawing and you want to keep track of changes on that drawing across public releases or even simple saves.

We can easily track changes, but since AutoCAD DWG do not support versioning, how can we keep information about original entities that have been changed or deleted?

Can we clone the object modified or deleted and store it somewhere in the same DWG? Probably yes, we'd provide a storage mechanism that do not interfere with AutoCAD and maybe store even related information, like layers, styles, etc. that risk to be removed from a simple purge.

You can also disable purge altogether, so deleted information would be retained.

But thinking to a standard document management, you must observe that you may be interested in tracking changes between document release (I mean when you check, approve and publish a document to be sent outside) and not between every single save.

For me, that I have already a document management in place, it's easy to think to keep a copy of released documents, while advancing revisions. This because I believe is more efficient to retrieve a datum version, without the need to be rebuilt if using a journal or a single file storage...

Also every revision can support purge and keep file weight at its minimum.

In this case we can use previous file versions to retrieve previous version of entities.

So far, we can even simply check every entities using their handles, that are persistent across sessions. Simply traverse a file, get each handle, find same handle in second file and see if exists or not. If it doesn't exist the entity has been created or deleted, depending if the first file you traverse is a subsequent or previous version (I wouldn't trust file dates to sequence the changes...).

If the handle exists, you know that the entity is still there, but is it changed? This is a whole problem by itself, because you should provide a entity compare for every type of entity... lengthy, but possible.

I think this is the way the Autodesk Plugin 'DWG Compare' works.

As an optimization I say: wouldn't be a lot easier if we know from start which handles have been changed, added or deleted?

This is when a journal would be helpful. We can easily attach event handlers to database and keep track of those handles and we can record those handles in a journal (an external file? a database? something stored inside the same DWG? Watch out for journal dimensions!).

Of course you can always track every changes, but save the journal portion only if saving the DWG.

An external journal file or database has the advantage o be accessed by multiple applications, so you can also add records when documents are checked, published, transmitted or revised.

So, when you want to show what's changed in a datum version from previous one or even multiple previous versions, you can read the journal and highlight changed or new entities. Loading in memory previous versions' DWG you can retrieve deleted entities and show them too, or retrieve different versions of the same entity and highlight them for compares!

This way should be quite fast while running and easy enough to implement...

Any more idea?

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Wed, 05 Oct 2016 05:24:57 GMT

Hi,

Your post is very helpful, I am also working on same functionality like Tracking Changes of Drawing. Here i am storing object id and its properties which are modified in my database, so that i can identify on which object what changes are done. But object Id of that entity is unique only for that session or that instance, so i am unable to find out which object was modified last time when i open my drawing again.

Is their any solution for this so that i can identify which object was modified and what changes are done last time when i close and reopen same drawing

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Wed, 05 Oct 2016 09:57:27 GMT

Simple, use Handles.

Handles are persistent

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

dgorsman — Wed, 05 Oct 2016 17:37:32 GMT

@Anonymous wrote:

Simple, use Handles.

Handles are persistent

But only unique within any given drawing. Different drawings may have identical handles for different entities.

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Thu, 06 Oct 2016 10:18:21 GMT

Sure, but aren't you going to manage separate journal for each dwg?

Also I guess the tracking system is going to run on multiple workstation, isn't it?

So I guess you must use a longer composite key to access you journal or db...

I use 'project + relative folder + file name' as a main document management key, since once inscribed to the management, publishing and revisions are handled by a wizard procedure, so I'm sure what files derive from. And there is limited possibility for published drawings... for us, once sent out you can open them only for reading, or start a new revision.

Another idea may be to create a GUID just to mark uniquely the document and store inside the document itself, so you are free to move and rename your files. Just remember to update your db at every saveas...

But you have also to layout how your management react for different actions.

For example, a saveas for us means a new independent branch, maybe a piece very similar but with different story by itself... a rename would just rename the current document (if not published), but keeping all the history, and so on...

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

dgorsman — Thu, 06 Oct 2016 15:33:44 GMT

abhay.nawale mentioned a database, not an in-document journaling system. Using handles that way can get you into trouble, even when drawing file name is used ie. users can delete the original file and rename another to the first name, then *blammo* that handle/drawing filename index that used to refer to a line is now referring to a block reference, or text, or something else that's completely different.

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

CADbloke — Fri, 07 Oct 2016 04:36:14 GMT

@Anonymous wrote:
Simple, use Handles.
Handles are persistent

Yes, and no. If the user modifies a block, re-sorts attributes, deletes, adds etc then the Handle can change. If they replace blocks with new blocks representing the same information then the handles will change but the information may be essentially unchanged.

What you use as your baseline and comparison criteria depends on your definition of constitutes a change.

btw, have you seen https://apps.autodesk.com/en/Detail/Index?id=136068404068200943&appLang=en&os=Win32_64 ?

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Fri, 07 Oct 2016 04:55:20 GMT

Thank you very much for this valuable information, now i got the idea that we can use handles but we need to check that whether blocks are removing modifying or adding in the drawing, if we are able to handle these things then we can achieve the target.

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Fri, 07 Oct 2016 06:03:24 GMT

@Anonymous wrote:

What you use as your baseline and comparison criteria depends on your definition of constitutes a change.

btw, have you seen https://apps.autodesk.com/en/Detail/Index?id=136068404068200943&appLang=en&os=Win32_64 ?

Exactly, a document management or a change tracker must define what are those criteria and act accordingly.... in the block example you made, I'd prefer to report the whole block change even if the block still remained the same... it will be maybe a false positive, but it'd be much difficult to really understand if something actually changed or not, or maybe changed, but graphically speaking remain the same (like a batch update of cleaned and purged blocks).

I tried DWG Compare and it's loaded in some machines just in case, but it's rarely used among my customers... firstly because it didn't give the expected results... at least in our cases...

Re: Need API Of DWG Compare App and for Tracking Drawing Changes

Anonymous — Fri, 07 Oct 2016 06:17:17 GMT

@dgorsman yes, you're right, apparently is almost impossible to control every action from users that wants to create troubles on purpose...

Currently, we have such a risk, but even not thinking about users, if it will be necessary to perform a partial file restore, we will going out of sync with database or viceversa...

But here we generally speak of custom applications for very specialized needs, to a generic customer with all the ifs and whens I'd probably suggest to go Vault....