Is the ʼExtrudeʼ tool the primary way to create 3D height in Rhino?

ByCADbrief Staff

Short Answer

Yes — in Rhino 3D, ExtrudeCrv is the primary and most common professional way to create 3D height from 2D curves. It is fast, reliable, and ideal for turning closed profiles into solids or open curves into surfaces. Limitation: it only works cleanly when the input curve is valid and properly planar.

What You Need to Know Before

Warning: If your curve is open, self-intersecting, or not truly planar, the extrusion may fail or create a surface instead of a closed solid. A very common mistake is assuming a visually flat curve is planar when Rhino detects small Z-value differences.

How to Create 3D Height in Rhino

  • Command: ExtrudeCrv

  • Shortcut: ExtrudeCrv

  • Quick Steps:

    1. Select the 2D curve, then type ExtrudeCrv in the command line, or use the Surface menu if available in your workspace.
    2. Specify the extrusion height by dragging in the viewport or entering a numeric distance in the command line.
    3. Set Solid=Yes for closed planar curves if you want a closed volume, then confirm the direction.

Variables & Settings

  • Key Setting: Solid=Yes/No

  • Expert Setting: This option controls whether Rhino caps the extrusion ends when the source curve is closed and planar. If Solid=No, Rhino creates open surfaces only, which is often the reason users think extrusion “failed.”

Why it Fails

  • Cause 1 (Geometry): The curve is not closed, is self-intersecting, or contains tiny gaps, so Rhino cannot build a proper solid.

  • Cause 2 (layers/Locks): The source object is on a locked layer or you are trying to extrude referenced geometry you cannot modify as expected.

  • Cause 3 (Command/Logic): The curve is not planar, so ExtrudeCrv may produce an unexpected result or refuse to cap the extrusion into a solid.

Quick Fix & Best Practice

  • Quick Fix: Run SelOpenCrv to find open curves, then use Join or repair gaps before running ExtrudeCrv again with Solid=Yes.

  • Manager’s Verdict: Use ExtrudeCrv as the default method for adding height to clean 2D profiles in Rhino. Avoid it for complex freeform shaping where commands like lofting, sweeping, or SubD modeling are more appropriate.

FAQ

Can Rhino extrude open curves?

Yes, but the result is typically a surface, not a closed solid.

What command should I use to extrude a surface instead of a curve?

Use ExtrudeSrf.

Why is Rhino not making a solid when I extrude?

Usually because the curve is not both closed and planar, or Solid=Yes was not enabled.

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