[Free LISP] Auto-mark revision clouds for design changes — compare two regions in same DWG

[Beastt1992]

Every design revision, I have to circle changes with revision clouds for submission. 
I kept missing things or marking the wrong spots, so I wrote a LISP to do it automatically.

What it does:
1. Select Region A (old version)
2. Select Region B (revised version)  
3. Red revision clouds appear around every difference

It works inside the same DWG — no need for two separate files like DWG Compare. 
Uses signature-based object comparison with sorted merge, so it handles 1400+ objects in seconds.

Features:
- Automatic spatial alignment (consensus voting)
- Nearby changes merged into grouped clouds
- Giant objects (title blocks, borders) auto-filtered
- Manual 2-point alignment fallback if auto fails
- Configurable tolerance, arc size, merge distance

Supports: LINE, CIRCLE, ARC, LWPOLYLINE, TEXT/MTEXT, INSERT, DIMENSION
Skips: HATCH (too many false positives)

AutoCAD 2014+ compatible. 

Free / MIT: https://github.com/beastt1992/DiffCheck

Feedback welcome

Edited 10 hours ago by Beastt1992
EXTRA LINK IN THE POST

[Steven P]

I tend to do this manually - often stretching lines one way or another to make way for other details, but these are not changes that need to be recorded - your LISP would record that though? Adding a cloud myself allows me to position it so that it is not on top of other entities.

[Beastt1992]

56 minutes ago, Steven P said:

I tend to do this manually - often stretching lines one way or another to make way for other details, but these are not changes that need to be recorded - your LISP would record that though? Adding a cloud myself allows me to position it so that it is not on top of other entities.

Hi Steven, spot on! The LISP definitely flags raw geometry changes, not design intent.

I actually use it as a "first pass" safety net. It's much faster to let the script cloud everything that moved and simply delete the few "false positives" (like lines stretched for spacing) than to manually hunt for actual design changes.

For the overlapping issue: the clouds are standard polylines on a dedicated layer. You can easily grip-stretch them out of the way, or use DFCT beforehand to increase the padding so they draw looser.

It doesn't replace a drafter's eye, but it definitely handles the heavy lifting of finding the changes first! Thanks for checking it out.