Can I bend a solid object along a custom curve in Rhinoceros 3D?

Short Answer

Yes — in Rhino 3D, you can bend a solid object along a custom curve using FlowAlongCrv, which is the most common professional method for matching geometry to a target path. It works best when the object is first built straight along a base curve. Limitation: complex solids can distort if the reference curves do not match well.

What You Need to Know Before

Warning: FlowAlongCrv can stretch, twist, or self-intersect closed or detailed solids if the base curve and target curve have very different lengths or curvature. This is especially risky with fillets, holes, or polysurfaces near the ends of the object.

How to Bend a Solid Along a Custom Curve

• Command: FlowAlongCrv

• Shortcut: No default shortcut

• Quick Steps:

  1. Select the solid, then run FlowAlongCrv from the command line or Transform menu.
  2. Pick the base curve the object was originally aligned to, then pick the target curve you want the solid to follow.
  3. Set options such as Rigid=No for true bending, then press Enter to complete the flow.

Variables & Settings

• Key Setting: Rigid=No or Rigid=Yes

• Expert Setting: Rigid=No deforms the solid so it actually bends along the target curve, which is the usual choice for this task. Rigid=Yes keeps the object shape rigid and only repositions it along the curve, so it will not produce a true bend.

Why it Fails

• Cause 1 (Geometry): The solid was not modeled relative to a clean base curve, so Rhino cannot deform it predictably along the target curve.

• Cause 2 (layers/Locks): The object or reference curve is on a locked layer, preventing valid selection during the command.

• Cause 3 (Command/Logic): The base curve and target curve have mismatched direction or very different length, causing flipped orientation, compression, or severe distortion.

Quick Fix & Best Practice

• Quick Fix: Use Dir to check and align curve direction before running FlowAlongCrv, and rebuild the target curve if it has uneven control point distribution.

• Manager’s Verdict: Use FlowAlongCrv when the part is designed straight and needs to follow a path for concept, industrial design, or non-uniform forms. Avoid it for precision mechanical parts unless you verify critical dimensions after deformation.

FAQ

Can I bend a polysurface instead of a single solid in Rhino?
Yes, FlowAlongCrv works on polysurfaces if the geometry is valid.

Is Bend better than FlowAlongCrv for a custom curve?
No, Bend is mainly for simple bend deformation, while FlowAlongCrv is better for a custom path.

Can I keep the object from stretching during the bend?
Yes, partially — matching base and target curve length helps reduce stretching.

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