Rhino 3D Tip: Use Rhino’s What Command to Identify Object Types and Validity

If you are not using Rhino’s What command regularly, you are likely missing one of the fastest ways to understand exactly what is in your model. It is a deceptively simple command, but it can save time whenever imported geometry behaves unexpectedly, solids refuse to boolean, or a file contains objects you cannot immediately identify.

The What command reports detailed information about selected objects directly in the command history. Instead of guessing whether something is a surface, polysurface, extrusion, block instance, mesh, or annotation object, Rhino tells you precisely what it is.

• Run the command: type What, then select one or more objects.
• Review object type: Rhino reports whether the object is an open surface, closed polysurface, extrusion, mesh, SubD, curve, hatch, block instance, or something else.
• Check validity: it will often indicate whether the object is valid, closed, solid, or contains issues that may affect downstream commands.
• Inspect structure: for curves and surfaces, it can reveal degree, point count, rational status, and other technical characteristics.
• Understand imported data: especially useful after bringing in DWG, STEP, IGES, or mesh files.

This matters because many Rhino commands depend on object type, not just appearance. Two objects may look identical in shaded view, but one could be a clean closed extrusion while the other is a fragmented polysurface with tiny gaps. What helps you catch that difference immediately.

Here are a few practical situations where the command becomes invaluable:

• Boolean troubleshooting: if a subtraction fails, use What to confirm both objects are actually closed solids.
• Export preparation: before sending a model to fabrication or 3D printing, verify that key parts are closed and valid.
• Imported geometry cleanup: determine whether geometry came in as lightweight extrusions, joined polysurfaces, or loose surfaces.
• Block auditing: quickly identify whether selected items are block instances rather than loose geometry.
• Curve diagnosis: check whether a curve is closed, planar, rational, or more complex than expected.

A good workflow is to pair What with other diagnostic tools:

• SelBadObjects to locate invalid entities.
• ShowEdges to reveal naked edges in polysurfaces.
• Properties for layer and attribute management.
• Check when you need additional object validation details.

One of the best habits you can build is to use What before fixing a problem, not after wasting time on the wrong assumption. If a surface will not offset, if a fillet fails, or if a part will not join, first confirm what the object really is. That quick inspection often points directly to the solution.

For Rhino users looking to sharpen daily modeling workflows, small commands like this often deliver the biggest efficiency gains. You can explore more Rhino tools, upgrades, and workflow resources through NOVEDGE’s Rhino collection. For broader CAD and 3D design insights, the NOVEDGE blog is also a valuable resource.

Tip: when something in Rhino looks right but behaves wrong, run What first. It is one of the fastest ways to replace guesswork with facts.

You can find all the Rhino products on the NOVEDGE web site at this page.