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Shape a smooth spline

Build a freeform curve from control points and reshape it without moving its ends.

About 5 minCadivari 0.3.0Watch and try

Useful first: Draw connected lines

An open spline passes through its first and last control points. Interior control points pull the curve toward them. With four points, Cadivari uses a cubic B-spline, so you can form a smooth outline with very few handles.
An open spline passes through its first and last control points. Interior control points pull the curve toward them. With four points, Cadivari uses a cubic B-spline, so you can form a smooth outline with very few handles.

An open spline passes through its first and last control points. Interior control points pull the curve toward them. With four points, Cadivari uses a cubic B-spline, so you can form a smooth outline with very few handles.

Try it in Cadivari

  1. Place four control points

    In a Top-plane sketch, press B or choose Spline. Click four well-spaced points in a gentle S arrangement. The dashed control polygon shows how those points influence the preview.

  2. Finish the open curve

    Press Enter or click the green check. While drawing, Backspace removes the last uncommitted control point; Esc cancels the whole unfinished spline.

  3. Move an interior control point

    Press V and select the spline. Drag one gold interior handle. Watch the curve and dashed polygon change while the endpoints stay fixed. Undo the completed drag with Ctrl + Z.

  4. Try a smoothing pass

    With the spline selected, click Smooth curve in Properties. It gently relaxes the control polygon while preserving open endpoints. Each click is a separate undoable edit.

  5. Make a separate closed loop

    Press B to start another spline. After at least three control points, move back to the first point until the snap turns green and click to close it. Select it to inspect the closure state in Properties.

Over to you

A small exercise

Create a four-point open spline, adjust one interior handle and undo. Then draw a separate closed spline and compare the Open and Closed states in Properties.

What you should see

The open curve stays anchored at its endpoints during the interior edit. The closed spline has a shared start and end handle that remains connected when moved.

Things to look out for

  • Interior control points usually do not lie on the curve. They control its shape rather than marking corners.
  • Pressing Enter finishes an open spline. To close it, snap back to its first point after placing at least three points.
Check your understandingDoes a spline pass through every control point

No. An open spline passes through its endpoints; its interior points influence the curve. Use the curve itself when judging the finished outline.

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Go deeper in the knowledge base

Instructions checked against the Cadivari 0.3.0 source and knowledge base on 2026-09-16. Lesson revision 1.