What is ʼEdge Continuityʼ in Rhino?

Short Answer

Edge continuity in Rhino means how smoothly two surface edges meet: position only (G0), tangent/slope continuity (G1), or curvature continuity (G2). The most common professional way to evaluate it is with MatchSrf or edge analysis tools while adjusting continuity options. Limitation: good edge continuity does not guarantee the whole surface is clean.

What You Need to Know Before

Warning: surfaces can look smooth in shaded view but still fail continuity checks at the edge, especially after trims or rebuilt patches. A very common hidden problem is matching trimmed edges instead of the underlying surface, which can produce unstable or misleading results.

How to Check or Create Edge Continuity

• Command: MatchSrf

• Shortcut: No default shortcut

• Quick Steps:

  1. Run MatchSrf from the command line, then select the surface edge you want to modify and the target edge to match.
  2. In the command options, set Continuity to Position, Tangency, or Curvature, depending on the required edge continuity.
  3. Turn on options like Refine match if needed, then confirm and inspect the result with Zebra or curvature analysis.

Variables & Settings

• Key Setting: Continuity

  This option controls whether the matched edge only touches the target edge (Position/G0), aligns directionally (Tangency/G1), or also smooths curvature transition (Curvature/G2). In production modeling, G1 is common for general surfacing, while G2 is preferred for higher-quality reflections.

Why it Fails

• Cause 1 (Geometry): the surfaces have poor underlying structure, bad degree/span layout, or heavily trimmed edges that cannot support a clean G1 or G2 match.

• Cause 2 (layers/Locks): one of the source or target objects is on a locked layer, so Rhino cannot modify the surface being matched.

• Cause 3 (Command/Logic): trying to force curvature continuity between incompatible surfaces can distort the result or fail because the edge conditions are too different.

Quick Fix & Best Practice

• Quick Fix: use Rebuild or RebuildEdges before MatchSrf if the edge is messy or the trim is unreliable, then re-run the continuity match.
• Manager’s Verdict: use G1 for most production joins and G2 only where reflection quality matters, such as Class-A style visible surfaces; avoid over-matching poor base geometry.

FAQ

What is the difference between G0, G1, and G2 in Rhino?

G0 is contact, G1 is tangent alignment, and G2 adds curvature smoothness.

How do I check if two Rhino surfaces are smoothly connected?

Use Zebra, Environment Map, or curvature analysis after running MatchSrf.

Does Join create edge continuity in Rhino?

No, Join only joins edges topologically; it does not improve geometric continuity.

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