How to turn a 2D drawing into a 3D solid in Rhino?

Short Answer

Yes — in Rhino 3D, the most common way to turn a 2d drawing into a 3d solid is to use ExtrudeCrv on closed, planar curves and enable the Solid option. This quickly creates a closed polysurface from 2D outlines. Limitation: open or non-planar curves will not produce a true solid.

What You Need to Know Before

Warning: If your 2D drawing contains tiny gaps, overlapping segments, or curves that are not truly closed, Rhino may extrude surfaces instead of a valid solid. Imported DWG linework is especially prone to this and often needs cleanup first.

How to Turn a 2D Drawing into a 3D Solid in Rhino

• Command: ExtrudeCrv

• Shortcut: ExtrudeCrv

• Quick Steps:

  1. Select the closed 2D curve(s), then type ExtrudeCrv in the command line.
  2. In the command options, set Solid=Yes and, if needed, keep BothSides=No for a standard one-direction extrusion.
  3. Enter the extrusion distance or pick the height in the viewport to create the 3D solid.

Variables & Settings

• Key Setting: Solid = Yes

• Expert Setting: This option tells Rhino to cap the extrusion and create a closed polysurface instead of just side surfaces. If Solid is set to No, the result will not be a true solid even if the source curve is closed.

Why it Fails

• Cause 1 (Geometry): The 2D profile is open, self-intersecting, or not planar, so Rhino cannot create a closed solid.
• Cause 2 (layers/Locks): The source curves are on a locked layer or mixed with hidden duplicate geometry, causing selection and extrusion problems.
• Cause 3 (Command/Logic): ExtrudeCrv was run with Solid=No, or the user extruded separate segments instead of first joining them into one closed boundary.

Quick Fix & Best Practice

• Quick Fix: Run Join on the outline, then use SelOpenCrv to detect any open curves before running ExtrudeCrv again with Solid=Yes.
• Manager’s Verdict: Use this method for most architectural, product, and fabrication workflows because it is fast and reliable. Avoid it when the 2D profile is messy or non-planar—clean the curves first.

FAQ

Can Rhino make a solid from open curves?
No, open curves usually create open surfaces, not solids.

What if my imported DWG will not extrude as a solid?
Check for gaps, overlaps, and unjoined segments, then repair the boundary.

Is ExtrudeCrv better than PlanarSrf first?
Yes, for most simple closed 2D shapes, extruding the curve directly is faster.

.