Detailed Mode or Basic Mode

Detailed Mode

In Detailed Mode, CompareDWG compares all entities in Modelspace. It also compares most of the tables, including the block definitions, and it compares the drawing variables. Finally reports are created.
Sophisticated inspection of result drawings is possible by viewing one or more of the result drawings (Old Drawing, New Drawing and/or Combined Drawing). Up to six colours are used to show changes, additions etc. In the result drawings, entity sets can be hidden, for example hiding the unchanged entities can make it much easier to inspect the changed entities.

Basic Mode

In Basic Mode CompareDWG loads the two drawings, colours each of them in a contrasting colour, then displays them on top of each other. Only two colours are used and only the Combined Drawing is available. The user must then visually inspect the result and decide where the differences are without being able to hide the unchanged entities. (Often a plot will make it clear where the overlapping entities are.)
No reports are available. No temporary files are stored.

AutoCAD Handles

The best alternative is to compare in Detailed Mode. Since this provides much more information, it should be used whenever possible. However, to use this mode both the Old and the New Drawing must be based on the same set of handles. (Handles are internal code numbers that AutoCAD attaches to entities.) In most cases, where one drawing is a newer version of the other drawing or where both drawings have been derived from the same parent drawing, handles are fine and the Detailed Mode can be used.

In the following cases handles may not be usable and you may have to use the Basic Mode:

  • if one or both of the drawings are AutoCAD R12 drawings without handles (saving handles was optional in AutoCAD R12).
  • if a drawing has been inserted into another drawing with WBLOCK and INSERT commands (this will modify the handles).
  • sometimes both drawings may use the same handle for a polyline (or other entity) where these polylines are really unrelated. CompareDWG will assume this is the same polyline and report it as Changed, where it would have been better to report it as Deleted in the old drawing and Added in the new drawing. This is not a serious problem, as in all cases it will still be reported as different.

If you are not sure about the handles, simply try to compare the files in Detailed Mode. If this looks as you expect, all is well. However, if this finds (almost) no unchanged entities then you should rerun the comparison in Basic Mode.

Tip: even if the handles are not usable, you could consider running a Detailed Comparison to obtain a Table Details Report. Since table entries are compared by name, not by handle, this can still produce a usable report.

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