Can I create a curve by clicking on specific points (InterpCrv) in Rhinoceros 3D?

ByCADbrief Staff

Short Answer

Yes — in Rhino 3D, you can create a curve by clicking specific points using interpcrv, which is the standard professional method for building a smooth curve through picked points. It is commonly used for tracing shapes, fairing profiles, and sketch-based modeling. Limitation: the curve must pass through every picked point, which can create unwanted waviness.

What You Need to Know Before

Warning: If your points are unevenly spaced or accidentally snapped to the wrong object, InterpCrv can produce lumpy or unstable geometry that is difficult to edit later. This is especially common when Osnaps like Near or Point are left on during dense curve picking.

How to Create a Curve Through Specific Points in Rhino 3D

  • Command: InterpCrv

  • Shortcut: InterpCrv

  • Quick Steps:

    1. Run InterpCrv from the Command line, or go to Curve > Free-Form > Interpolate Points.
    2. Click the points in order where you want the curve to pass; use Osnaps such as Point or End if you need exact placement.
    3. Press Enter to finish, then choose a real option such as Degree=3 for a smooth curve or adjust Knots=Uniform/Chord if prompted.

Variables & Settings

  • Key Setting: Degree

  • Expert Setting: Degree controls curve smoothness and flexibility. Degree 3 is the most common professional choice because it gives a smooth interpolated curve without becoming unnecessarily hard to control. Higher degrees can overcomplicate the shape and make fairness worse.

Why it Fails

  • Cause 1 (Geometry): Picked points are too close together, out of order, or unevenly spaced, causing the interpolated curve to ripple or loop unexpectedly.

  • Cause 2 (layers/Locks): Target reference objects or point objects are on locked layers, so snapping or point selection does not behave as expected.

  • Cause 3 (Command/Logic): InterpCrv forces the curve through every selected point, so it is the wrong choice when you want a looser control-vertex style curve; CurveThroughPt logic does not simplify bad point placement.

Quick Fix & Best Practice

  • Quick Fix: Rebuild the result with Rebuild using a sensible point count and degree 3, or redraw with fewer, better-spaced clicks using InterpCrv.
  • Manager’s Verdict: Use InterpCrv when the curve must pass through known points exactly. Avoid it for design intent curves where clean control and easy editing matter more than exact point penetration.

FAQ

Can InterpCrv snap to existing object points in Rhino?
Yes, use Osnaps like Point, End, or Near while placing the interpolation points.

Is InterpCrv better than Control Point Curve?
No, it is better only when the curve must pass through specific picked points.

Can I edit an InterpCrv after creating it?
Yes, but heavy editing is often harder than with a control-point curve.

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