Compare two drawing revisions
Nomic overlays two sheets and reports each difference as a link. Red is the earlier sheet, blue is the later one, and black is what they share.
Start in chat
- Attach both drawings to a new conversation. They can be two PDFs, two pages of one PDF, or two folders of sheets.
- Click the Compare drawing revisions starter chip, or ask in your own words. For example, "What changed on A-201 between revision 2 and revision 3?"
- Say which sheet is older when the file names don't make it obvious. Nomic draws the older sheet in red and the newer one in blue, so swapping them reverses the reading.
Sheets at different scales, sheet sizes, or orientations are fine. You can also compare across disciplines, such as structural framing over the architectural plan, or a shop drawing against its contract sheet.
Open a change
Click any comparison link in the reply. The viewer opens both sheets overlaid and cropped to that change.
Use the Compare palette in the top-right corner of the viewer:
| To | Do this |
|---|---|
| See the whole sheet | Pick Full sheet (or Cited area to go back) |
| See one sheet alone | Click its Before or After row |
| Flip between Before and After | Press F with your pointer over the viewer |
| Hide a sheet | Click its eye icon |
| Get the palette out of the way | Click the minus icon to collapse it |
| Leave the comparison | Click the X |
Get a comparison image
PDF exports don't include the overlay. Ask Nomic for the comparison image instead: each comparison is saved to the conversation's session folder, and Nomic links the saved image.
If the comparison looks wrong
- The whole sheet is red and blue on two issues of one sheet. The sheets didn't line up. A telltale sign is the grid or building outline doubled as a red line next to a blue one. Ask Nomic to re-register the sheets using grid intersections at opposite corners.
- Text is a red and blue smear. That text moved or changed. Press F to read each sheet on its own.
- The viewer header says No overlay. That viewer can't draw the comparison, so it shows one sheet. Report it with the conversation link.
- A drawing review doesn't show comparison links. Drawing reviews cite each compared sheet with a callout instead. Ask for the comparison in a regular conversation.