# SPLINEDIT in AutoCAD

> How AutoCAD's SPLINEDIT (SPE) works: Close, Join, Fit data, Edit vertex, convert to Polyline and Reverse, prompt by prompt. Try it free in your browser.

SPLINEDIT edits a spline. Pick one at `Select spline:`, or select it before the command; double-clicking a spline runs SPLINEDIT on it too. Anything else says `Object selected is not a spline.` and asks again; a polyline fitted by PEDIT's Spline is turned into a spline of the same curve, without a word. Then it asks for an option again and again, each applied at once, until `EXit` or Enter. The spline shows its fit points' grips, and while you edit its vertices, its control vertices and frame. The whole edit is one step that `U` takes back. Typed `'ZOOM` works at any of its prompts.

- **Command:** `SPLINEDIT`
- **Aliases:** `SPE`
- **Panel:** [Modify](https://mellowcad.com/docs/commands.md#modify)
- **Try it:** [Open the editor](/draw), type `SPE` and press Enter.

## At the command line

The engine draws it and writes its history as you would type it: the prompts in AutoCAD 2027's order, with the same option letters.

A spline through five fit points, closed by SPLINEDIT: a smooth loop through them all.

```text
Command: SPLINEDIT
Select spline:
Enter an option [Close/Join/Fit data/Edit vertex/convert to Polyline/Reverse/Undo/eXit] <eXit>: C
Enter an option [Open/Fit data/Edit vertex/convert to Polyline/Reverse/Undo/eXit] <eXit>:
```

## Options

### `Close` (`C`)

Closes the spline smoothly: a fit spline through its fit points, a CV spline on its vertices. On a closed spline the option is `Open`, and Join is not offered.

### `Join` (`J`)

Joins open curves that meet its ends, by JOIN's rules for a spline, and says how many it joined.

### `Fit data` (`F`)

Edits the points the spline passes through. A CV spline, which has none, is first given fit points on its curve. Its options: `Add` picks a fit point and adds new ones after it, again and again (at an open spline's first point, `After` or `Before`); `Delete` removes fit points, down to two, three on a closed spline (`Cannot delete beyond this.`); `Move` steps through the fit points with `Next` and `Previous`, or `Select`, and moves the current one to the point you give; `Purge` drops the fit data, leaving a CV spline; `Tangents` sets the start and end directions, or `System`; `Close` and `EXit` as at the first prompt. A pick that is no fit point says `Not a fit point.`.

### `Edit vertex` (`E`)

Edits the control vertices; a fit spline loses its fit data at the first edit. `Add` puts a vertex at the point you pick on the spline; `Delete` removes one, down to two, three on a closed spline; `Elevate` raises the order, up to 26, never down; `Move` moves vertices, stepping as Fit data's Move does; `Weight` sets a vertex's weight, after `Spline is not rational. Will make it so.`, so the curve pulls nearer to it or further away. A pick that is no vertex says `Not a control vertex.`.

### `convert to Polyline` (`P`)

Asks a precision from 0 to 99, 10 by default, and replaces the spline with a polyline of straight segments, more of them the higher the precision; a 3D polyline where the spline does not lie flat, parallel to the XY plane. It ends the command. The precision is kept for the session, and PEDIT's conversion uses it too.

### `Reverse` (`RE`)

Turns the spline round, its first point last: `Spline has been reversed.`.

### `Undo` (`U`)

Takes back the last option, a whole Fit data or Edit vertex at once. With none left: `Command has been completely undone.`.

### `eXit` (`EX`)

Ends the command, as Enter does.

## What it does not do yet

Kink, which puts a sharp corner at a fit point or vertex; toLerance, which refits the spline within a tolerance; Tangents of a closed spline. convert to Polyline makes far more vertices of a fit spline than AutoCAD does, never arcs, and always replaces the spline. Group at `Select spline:`. The `+` AutoCAD draws on the current point while you step through the points.

[What it does and still lacks, in detail (in English)](https://github.com/ovelilla/mellowcad/blob/main/docs/coverage/modify.md#splinedit--spe--es-editspline--spe--pt-br-editarspline--espl)

## Questions

### What is the shortcut for SPLINEDIT in AutoCAD?

`SPE`, then Enter or Space. The full name works too, and `_SPLINEDIT` in any language of AutoCAD. Double-clicking a spline also runs it.

### How do I convert a spline to a polyline?

Run SPLINEDIT, pick the spline and choose `Polyline`; a precision of 10 gives a smooth polyline. [`PEDIT`](https://mellowcad.com/docs/commands/pedit.md) on a spline offers to convert it too.

### How do I add or move points on a spline?

Choose `Fit` to work on the points it passes through, then `Add` or `Move`. Choose `Edit` to work on the control vertices that frame it.

### How do I close a spline?

Choose `Close`: it closes smoothly, without a corner where it meets itself. `Open` opens it again.

### How do I join two splines?

Choose `Join` and select the spline whose end meets this one's, or use [`JOIN`](https://mellowcad.com/docs/commands/join.md).

## Related commands

- [SPLINE in AutoCAD](https://mellowcad.com/docs/commands/spline.md)
- [PEDIT in AutoCAD](https://mellowcad.com/docs/commands/pedit.md)
- [JOIN in AutoCAD](https://mellowcad.com/docs/commands/join.md)
- [LIST in AutoCAD](https://mellowcad.com/docs/commands/list.md)