If you need to edit splines in AutoCAD, the SPLINEDIT command (often referred to as the splinedit shortcut) is the built‑in tool for modifying splines and spline‑fit polylines. This guide explains what the command does, how to use it step‑by‑step, common problems and fixes, alternative methods, and practical tips to help you edit splines reliably.
What is the splinedit shortcut?
SPLINEDIT is the AutoCAD command used to edit an existing spline or a spline‑fit polyline. It gives access to common spline editing actions such as inserting/removing edit points, moving control vertices or fit points, opening or closing the spline, rebuilding its definition, and converting a spline into a polyline.
- The command can work with two different spline types: fit‑point splines (created from fit points) and control‑vertex (CV) splines (defined by control vertices).
- The exact options shown at the command line depend on the spline type and the AutoCAD version, but typical subcommands include Insert, Remove, Move, Rebuild, Open/Close, Convert to Polyline, and options to edit control vertices (CV) or fit points.
When and why to use SPLINEDIT
Use SPLINEDIT when you need to:
- Fine‑tune the shape of a spline by moving or adding fit points or control vertices.
- Change whether a spline is open or closed.
- Convert a spline to a polyline for operations that require polylines (e.g., some CAM or export workflows).
- Rebuild a spline to change degree or number of control points (when available).
- Correct or refine geometry imported from other software that created splines.
Examples:
- Smooth a curve that was drawn roughly with a polyline by converting to a spline and editing fit points.
- Convert a decorative spline to a polyline before using PEDIT or joining operations.
How to use SPLINEDIT — Step by step
Activate the command:
- Type SPLINEDIT on the command line and press Enter.
- Or use the ribbon: Modify > Edit Spline (if available in your workspace).
Select the spline:
- When prompted, click the spline or spline‑fit polyline you want to edit.
Choose an option:
- After selection AutoCAD displays available options on the command line. Typical options include:
- Insert — add a fit point or CV.
- Remove — delete a fit point or CV.
- Move — move a specific fit point or CV.
- Open / Close — change the spline between open and closed.
- Rebuild — change the number of CVs or degree (if present).
- Convert to Polyline (Pline) — convert the spline to a polyline with a specified tolerance.
- Type the short letter (shown in the prompt) or click the option.
- After selection AutoCAD displays available options on the command line. Typical options include:
Edit points or parameters:
- When editing points, pick the point to modify and either pick a new location or enter coordinates.
- For conversion to polyline, you’ll be asked for a precision/tolerance value (smaller value = closer match to original spline but more vertices).
Finish:
- Repeat options as needed; press Enter or Esc to exit the command.
Practical example — convert a spline to a polyline:
- Type SPLINEDIT → select spline → choose Convert to Polyline (or type the letter shown, often “Pline”) → enter a tolerance (e.g., 0.01) → press Enter. The spline becomes a polyline composed of many short segments approximating the original curve.
Alternative methods to edit splines
- Grip editing: Select the spline and use displayed grips to move fit points or control vertices directly — faster for simple moves.
- Properties palette: With the spline selected, open the Properties palette to change degree, rational settings, and other numeric properties (depends on spline type).
- Explode (with caution): Exploding a spline may convert it into a polyline or lines/arc segments depending on the object and version — use when you need segment-level control, but saves only after testing.
- Create a new spline: If editing fails or is cumbersome, redraw the curve using the SPLINE command using fit points/control points and delete the original.
- PEDIT: After converting a spline to polyline, use PEDIT to join, smooth, or edit polyline vertices.
Why SPLINEDIT may not work — common problems and fixes
Problem: Command seems to do nothing or not list expected options.
- Fix: Ensure you actually selected a spline. If the object is a regular polyline or a 3D polyline, SPLINEDIT won’t show spline options. Use PEDIT for polylines.
Problem: Spline is part of a block or xref and cannot be edited.
- Fix: Explode or edit block In‑Place (REFEDIT) or unlock the xref if allowed. For xrefs, edit the source drawing.
Problem: Object on a locked or frozen layer.
- Fix: Unlock/unfreeze the layer before editing.
Problem: Spline was created as a spline‑fit polyline and some SPLINEDIT options differ.
- Fix: If needed, convert to a true spline or adjust workflow: convert to polyline only if you need segments, or recreate the curve with SPLINE for full spline edit options.
Problem: No grips visible or grips disabled.
- Fix: Ensure GRIPS system variable is set to 1, and Selection Cycling or grips are enabled in options.
Problem: Command unavailable in your AutoCAD flavor or older version.
- Fix: Use alternative editing methods (grips, Properties, recreate spline). Check Autodesk documentation for your version; consider updating or using equivalent commands.
Problem: Conversion to polyline yields poor approximation or too many vertices.
- Fix: Adjust the tolerance value when converting: smaller tolerance → more vertices but better accuracy; larger tolerance → fewer vertices but rougher curve.
Problem: Spline from imported file behaves unexpectedly.
- Fix: Run AUDIT and RECOVER on the drawing, or recreate the curve manually. Consider exporting/importing with different settings.
Practical tips & best practices
- Use grips for quick edits (move, stretch) and SPLINEDIT for structural changes (insert/delete/rebuild).
- When converting to polyline, test tolerance values on a copy of the object to find a balance between accuracy and vertex count.
- If you need tight control over curve shape for CNC or CAM, convert to polyline with a precise tolerance, then simplify vertices as required.
- Keep a backup or use a separate layer before destructive actions like explode or convert.
- Use the Properties palette to inspect whether a spline is defined by Fit points or Control vertices — this determines which SPLINEDIT options are applicable.
- Customize a Command alias (in acad.pgp) for faster access if you frequently edit splines.
FAQ
How do I tell if an object is a spline or a polyline?
Select the object and look at the Properties palette: it will list the object type as Spline, Polyline, or 3D Polyline. Spline objects have properties like Degree, Fit tolerance, Control points, or Fit points.
Can I convert a spline back from polyline to spline?
You cannot directly convert a polyline into a true spline with exact original parameters. You can recreate a spline by using the SPLINE command and snapping to polyline vertices or fit points to approximate the shape.
What tolerance should I use when converting a spline to a polyline?
There is no single value; common starting points are 0.01 or 0.001 units depending on drawing scale. Smaller values give closer fits but increase vertex count. Test on a copy of the object.
Why are some SPLINEDIT options missing?
Options vary by spline type (fit‑point vs CV spline) and AutoCAD version. Also, if the object is not a true spline (e.g., spline‑fit polyline or 3D polyline), only a subset of edit options is available.
My spline is inside a block — how can I edit it?
Use REFEDIT or BEDIT to edit the block definition, or explode the block (if acceptable) to edit geometry. Always make a backup of the block before destructive edits.
SPLINEDIT didn’t work and my drawing shows errors — what should I do?
Run AUDIT and RECOVER on the drawing to fix database issues. If errors persist, copy the geometry into a New drawing or recreate the spline.
Are there keyboard shortcuts or aliases for SPLINEDIT?
By default the command is SPLINEDIT. You can create or edit an alias in the acad.pgp file (command aliases) to shorten it (for example, assign SPE to SPLINEDIT).
I need to smooth a polyline — should I convert to spline?
Yes, you can create a spline from polyline vertices using SPLINE (pick polyline vertices as fit points), then edit the spline as needed. Alternatively, use PEDIT > Spline (if available) to create a spline fit from a polyline.