SPLINE (Command)¶

Creates a smooth curve that passes through or near a set of fit points. Splines produce flowing, organic curves ideal for contours, profiles, and freeform shapes.

Quick start

Toolbar > Draw > Spline, or type SPLINE in the Command Panel

Prompts¶

Prompt	Description
Specify start point	Starting point of the spline (first fit point)
Specify next point	Additional points — the curve adjusts to pass through each point smoothly

Keywords¶

Keyword	Availability	Description
Undo	Always (after first point)	Removes the last specified point
Close	After 3+ points	Closes the spline loop back to the first point

How to Use¶

Start the Spline command
Click or type coordinates for the first point
Continue clicking to add fit points -- the smooth curve updates in real time
Press Enter to finish, or type C to close the spline

Command: SPLINE
Specify first point: 0,0
Specify next point: 30,40
Specify next point: 60,10
Specify next point: 90,50
Specify next point: [Enter]      --> spline through 4 points

Options During Creation¶

Undo¶

Type Undo to remove the most recently placed point without ending the command. You can undo multiple points in sequence.

Close¶

Type Close (available after 3 or more points) to connect the last point back to the first, creating a closed spline loop.

Command: SPLINE
Specify first point: 0,0
Specify next point: 40,30
Specify next point: 80,0
Specify next point: 60,-30
Specify next point: Close        --> smooth closed loop

Note

Closed splines maintain curvature continuity (C2) around the entire loop, ensuring a smooth transition at the closure point.

Input Methods¶

All points accept:

Method	Example	Result
Mouse click	Click on the sheet	Point at cursor position
Absolute coordinates	`50,100`	Point at X=50, Y=100
Relative coordinates	`@30,40`	Offset from last point
Polar input	`50<45`	50 units at 45 degrees from last point
Snap to geometry	Click with Osnap enabled	Precise placement on existing entities

Precision Aids¶

Aid	Effect
Ortho	Constrains direction to horizontal/vertical
Grid Snap	Snaps points to grid intersections
Entity Snap	Snaps to Endpoint, Midpoint, Center, Intersection, etc.
Entity Track	Alignment guides from reference snap points

Editing Splines¶

Grip Editing¶

Select a spline to display fit point grips:

Drag a fit point to reshape the curve -- the spline adjusts smoothly through the new position
Add points by clicking on the spline and using the context menu
Delete points to simplify the curve

Properties Panel¶

Property	Description
Fit points	Coordinates of each through-point
Closed	Whether the spline forms a closed loop
Color	ByLayer or explicit color
Layer	Layer the spline is placed on
Thickness	Line thickness
Stroke	Line style (solid, dashed, etc.)

Examples¶

Smooth Contour Line¶

Command: SPLINE
Specify first point: 0,0
Specify next point: 20,15
Specify next point: 50,5
Specify next point: 80,20
Specify next point: 100,0
[Enter]

Closed Organic Shape¶

Command: SPLINE
Specify first point: 0,0
Specify next point: 30,40
Specify next point: 70,40
Specify next point: 100,0
Specify next point: 70,-30
Specify next point: 30,-30
Specify next point: Close         --> smooth closed loop

Spline Through Snapped Points¶

Enable Endpoint and Midpoint snaps in the Status Bar
Start SPLINE
Click on existing geometry points -- the spline passes through each snapped location
Press Enter to finish

Best Practices¶

Practice	Benefit
Use fewer fit points for smoother curves	Fewer points = less waviness; add only where needed
Snap to existing geometry	Spline connects precisely to reference points
Use Close for loops	Ensures smooth curvature continuity at the closure
Edit with grips after creation	Fine-tune the shape without redrawing
Draw on the correct layer	Set layer in Format Panel before drawing
Use splines for organic shapes	Better than arcs for flowing, non-circular curves

Quick Reference¶

Task	Input
Start spline command	`SPLINE` or Toolbar > Draw > Spline
Place fit points	Click or type coordinates for each point
Undo last point	Type `Undo`
Close the spline	Type `Close` (after 3+ points)
End the command	`Enter` or `Esc`
Edit shape after creation	Select spline, drag fit point grips
Add more points	Select spline, context menu > Add Point