Rhino 3D Tip: Validate Curve Quality with CurvatureGraph for G2/G3 Continuity

Use CurvatureGraph to validate curve quality before surfacing. It reveals radius changes, flat spots, kinks, and ripple artifacts so you can lock in G2/G3 continuity with confidence.

Quick start

• Select curves and run CurvatureGraph.
• Adjust Scale so the tallest combs are visible but not clipping the view.
• Increase Density/Samples for closer inspection in tight areas; reduce for long, simple spans.
• Use CurvatureGraph again to toggle off (or CurvatureGraphOff if you prefer a dedicated command).

How to read the comb

• Height ≈ 1/Radius: taller spikes indicate tighter curvature (smaller radius); short spikes indicate flatter areas (larger radius).
• Direction: combs point toward the instantaneous center of curvature—helpful when comparing adjacent curves.
• Smoothness: an even, gradually changing comb indicates fair curvature. Sudden jumps or oscillations signal ripples or stacked knots.
• At joins:
  • G0 (position only): a break in the comb with no alignment.
  • G1 (tangent): comb direction aligns but heights differ at the join.
  • G2 (curvature): both direction and height match seamlessly at the join.
  • G3+: the rate of change matches—look for very smooth transitions without inflection noise.

Workflow to diagnose and fix issues

• Unify directions with Dir before comparing multiple curves.
• Remove unnecessary structure:
  • FitCrv to a tight tolerance to reduce knots while preserving shape.
  • Rebuild (degree 5 is a good starting point for Class-A-like work) to even out control spacing.
  • RemoveMultiKnot or RemoveKnot to eliminate stacked knots that cause comb spikes.
  • Fair to gently smooth small ripples without destroying intent.
• Rebuild transitions:
  • BlendCrv or Match with G2/G3 options to unify joins.
  • Enable History on blends/matches so edits update the curvature comb live.
• Recheck with CurvatureGraph and fine-tune Scale and Density to validate the final flow.

Pro tips

• Scale heuristic: aim for the tallest comb to be about 5–10% of the curve span for a readable display.
• Isolate suspect areas with Isolate or a clipping plane to keep the view clean while you adjust.
• Use Curvature (command) at key points to read numeric radius; compare with design intent.
• Before surfacing, ensure input curves achieve the target continuity—surface tools can only follow what curves provide.
• For mirrored designs, analyze one side, then Mirror after locking in G2/G3 on the source side.

Related checks

• After surfacing, validate with Zebra and EnvironmentMap to confirm continuity visually.
• Use EdgeContinuity to verify surface-to-surface G0/G1/G2 at trims.

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