Capabilities
Drawing Overlay
Ask Nomic to compare two sheets and it lays one over the other, the way a light table or Bluebeam's overlay does. Linework only on the earlier sheet is red, linework only on the later sheet is blue, and anything the two share is black. Each change Nomic reports is a link: click it and the viewer opens both sheets overlaid and cropped to that change.
Watch two revisions of a reflected ceiling plan overlaid in the viewer.
Key Use Cases
Ask for a comparison
Attach both drawings to a conversation, or include them through a project, and ask. The Compare drawing revisions starter chip on a new conversation does this for a whole set. You can also ask in your own words:
“What changed on A-201 between revision 2 and revision 3?”
“Overlay the structural framing plan on the architectural floor plan and flag beams that land in open space.”
“Compare this shop drawing against contract sheet S-301.”
The two sheets don’t need to match in scale, sheet size, or orientation. Nomic registers them from their own linework. Two issues of the same sheet should come out nearly all black, with color only where something changed. Two disciplines of the same building come out mostly colored, because they draw different things; the shared column grid and building outline should still line up in black.
Nomic replies with a list of what was added, removed, or changed. Each item is a comparison link to that spot on the sheet.
Open a change in the overlay
Click a comparison link in the reply. The viewer opens the later sheet with the earlier one drawn over it, cropped to the change Nomic cited. The rest of the sheet is washed out so poor alignment elsewhere doesn’t look like a change.
The Compare palette in the top-right corner of the viewer controls the overlay:
Cited area / Full sheet — Compare just the cited change or the whole sheet. Links that cite a whole sheet open to the full sheet and don’t show this switch.
Before (red) and After (blue) — Click a row to show that sheet alone; click it again to show both. The eye icon hides that sheet.
F — With your pointer over the viewer, flip between Before and After to spot what moved.
Collapse the palette to a small chip with the minus icon, or close the comparison with the X.
Opening the same link again starts fresh: both sheets, cropped to the cited area.
Keep the comparison image
Every comparison Nomic runs is also saved as an image in the conversation’s session folder. Ask for the comparison image and Nomic links it. The link opens the image in the viewer, and the file stays in the session folder for sharing outside Nomic.
Reading the colors
| Color | Means |
|---|---|
| Red | Only on the earlier sheet (Before): removed or moved from here |
| Blue | Only on the later sheet (After): added or moved to here |
| Black | On both sheets: unchanged |
Moved text prints twice, red across blue, and is often unreadable in the overlay. Flip between Before and After with F to read each value. If grid lines or the building outline show as a red line beside a blue twin at a constant offset, the sheets didn't register; ask Nomic to re-register them before trusting the changes it lists.
Where comparisons appear
Comparison links open the overlay from a chat reply, a Markdown artifact, or an ordinary table. Some places don't show it yet:
- Drawing reviews. The Drawing Review artifact doesn't render comparison links. Findings that compare two sheets cite each sheet with its own callout instead.
- Exported PDFs. An annotated PDF doesn't include the overlay. Use the saved comparison image instead.
- The legacy PDF viewer. If the viewer header shows No overlay, that viewer can't draw the comparison and shows only one sheet.