Step 6: 3D Geometry Traces¶

Purpose¶

Establish the intrados lines that Step 7 will measure. Traces can come from automatic extraction, imported 3DM curves, or both.

Trace sources¶

Automatic traces¶

The application can derive candidate rib lines automatically from processed imagery using edge detection and skeletonisation, then split the result into individual line candidates.¹ This gives you a fast starting point rather than a finished scholarly interpretation.

Automatic traces work best where ribs are clearly separated and well captured in the scan.

Manual traces from Rhino 3DM¶

If you have manually traced the rib geometry in Rhino or another tool that exports 3DM, you can import those traces directly. Manual traces are preferable when automatic extraction is unreliable.

To import: click Import 3DM, select the file, and map the Rhino layer names to the corresponding rib identifiers in the application.

What you do here¶

1. Inspect automatic traces. Review the detected lines in the 3D canvas.

2. Import manual traces (optional). If automatic extraction is unsatisfactory for some or all ribs, import a 3DM file and review the imported lines.

3. Compare sources. If you have both automatic and manual traces, compare them side by side.

4. Select the active trace set. Choose whether to use automatic traces, manual traces, or both.

5. Save the confirmed trace set before moving to Step 7.

Interface controls¶

Control	What it does
Automatic / manual / combined toggle	Switches which trace source is shown and used downstream
Import 3DM button	Opens a file browser to load a Rhino 3DM file
Rib list	Lists all detected or imported traces; click to highlight in the 3D canvas
Visibility toggles	Show or hide automatic and manual trace overlays independently
Save button	Confirms the active trace set for Step 7

What to check before moving on¶

• The main ribs you intend to measure each have a usable trace.
• Traces follow the rib centre as closely as practical.
• Obvious spurious lines have been excluded.

Expected result¶

A confirmed set of traces ready for measurement in Step 7.