What is ʼShow Edgesʼ and ʼNaked Edgesʼ in Rhino?
Short Answer
In Rhino, ShowEdges is the standard tool used to inspect edge conditions on surfaces and polysurfaces, including naked edges, which are edges not joined to another surface. Professionals commonly use it to find gaps before joining, offsetting, or creating solids. It only reports edge status; it does not repair geometry.
What You Need to Know Before
Warning: Naked edges often indicate tiny gaps, bad trims, or unjoined faces that can cause Boolean failures, bad offsets, or non-watertight exports for STL and STEP. A model can look closed on screen but still fail manufacturing or meshing because of these edge defects.
How to Find Show Edges and Naked Edges in Rhino
Command: ShowEdges
Shortcut: No default shortcut
Quick Steps:
- Select the surface or polysurface, then run ShowEdges from the command line.
- In the Show Edges options, enable Naked edges and, if needed, also check Non-manifold edges.
- Review the highlighted edges in the viewport, then use Zoom or sub-object inspection to locate the problem areas.
Variables & Settings
Key Setting: Naked edges toggle in the ShowEdges command options
Expert Setting: Turn on Non-manifold edges when checking complex joined geometry. Naked edges show open boundaries, while non-manifold edges reveal invalid edge sharing conditions that can also break solid workflows.
Why it Fails
Cause 1 (Geometry): Adjacent surfaces do not actually meet within Rhino’s absolute tolerance, leaving open edges that show as naked.
Cause 2 (layers/Locks): Part of the object may be on a locked or referenced workflow state, preventing proper editing after naked edges are found.
Cause 3 (Command/Logic): Users often expect ShowEdges to fix the model automatically, but it is only an analysis command and must be followed by Join, MatchSrf, ExtendSrf, or rebuilding steps.
Quick Fix & Best Practice
Quick Fix: Run Join first; if edges still remain naked, use MatchSrf or rebuild/extend the surrounding surfaces, then run ShowEdges again.
Manager’s Verdict: Use ShowEdges as a required QA check before Booleans, shelling, and export. If naked edges remain, do not assume the model is production-ready, especially for CAM, 3d printing, or exchange to other CAD systems.
FAQ
Does ShowEdges repair naked edges automatically?
No, it only highlights edge conditions for inspection.
What is a naked edge in Rhino?
It is an edge of a surface or polysurface that is not joined to another adjacent edge.
Can a closed-looking model still have naked edges?
Yes, display shading can hide small gaps that ShowEdges will detect.
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