Rhino 3D Tip: Diagnose Naked, Boundary, and Non‑Manifold Edges with ShowEdges

When joins fail or 3D prints leak, run ShowEdges to reveal where geometry is open or topologically suspect. It’s a fast, visual way to diagnose and fix problems. If you need Rhino or plug-ins, check out NOVEDGE.

What ShowEdges reveals

• Naked edges: Edges of a surface or polysurface that are not joined to a neighbor. These create leaks in “solid” models.
• Boundary edges: The outer perimeter of an open surface or polysurface—useful to understand where an object is intentionally open.
• Non-manifold edges: Edges shared by more than two faces or with ambiguous topology. These break many downstream operations.

How to use it

• Path: Analyze > Edge Tools > Show Edges, or type ShowEdges.
• Select the surface or polysurface to inspect.
• Enable Naked edges, Non-manifold edges, and/or Boundary edges as needed.
• Use the selection/zoom options in the dialog to isolate problem edges quickly.
• Toggle off ShowEdges when done to clear the highlights.

Typical fixes, by symptom

• Tiny gaps after Join
  • Adjust model tolerance first: DocumentProperties > Units > Absolute tolerance. Many gaps are smaller than your current tolerance.
  • Use RebuildEdges to refit trimmed edges to underlying surfaces; then Join again.
  • If the gap is planar, DupBorder and create a PlanarSrf, then Join.
• Misaligned or short edges
  • ExtendSrf to overlap neighbors, then Trim and Join.
  • MatchSrf with Position/Tangent as appropriate to align edges before joining.
  • For organic transitions, BlendSrf to bridge tricky edge pairs.
• Missing patches or holes
  • DupEdge or DupBorder to capture the opening; Patch for irregular shapes, PlanarSrf for flat loops, or Sweep/Loft where continuity matters.
  • Cap planar openings on closed loops with Cap or CapHole.
• Non-manifold situations
  • Explode, then Separate conflicting faces and resolve overlaps; re-Join cleanly.
  • Avoid JoinEdge as a routine fix; it forces joins without improving geometry and can hide issues until later operations fail.

Pro tips

• Run ShowEdges before Booleans and before exporting for 3D printing/CAM to catch leaks early.
• Create a quick alias: for example, NE = _ShowEdges _Naked=_Yes _NonManifold=_Yes _Boundary=_No.
• Use EdgeContinuity to evaluate G0/G1 matches along joined edges where aesthetics or aerodynamics matter.
• Pair with Zebra or CurvatureGraph on adjacent surfaces to diagnose continuity before committing to joins.
• Keep your display mode contrasty so highlighted edges stand out; consider a custom analysis color.
• For licenses, upgrades, and expert advice, visit NOVEDGE or browse the NOVEDGE blog for more Rhino tips.

A clean model is a reliable model. Make ShowEdges part of your routine checks to save time, prevent failed Booleans, and deliver watertight results ready for fabrication. Need tools or guidance? The team at NOVEDGE can help.