SPLINE

Access Methods

Button

Ribbon: Home tab

Draw panel

SplineNot available on the ribbon in the current workspace

Menu: Draw

SplineNot available in menus in the current workspace

Toolbar: Draw

Summary

There are two methods for creating splines in AutoCAD: with fit points or with control vertices. Each method has different options.

Control the display of the control vertices with the CVSHOW and CVHIDE command.

List of Prompts

The following prompts are displayed.

Method

Controls whether the spline is created with fit points or control vertices. The options differ depending on whether you select Options for Splines with Fit Points or Options for Splines with Control Vertices.

Fit: Draw a spline by specifying fit points.

Changing the Method updates the SPLMETHOD system variable.
Control Points: Draw a spline by specifying control vertices.

This is the preferred method if you are creating geometry to use with 3D NURBS surfaces. Changing the Method updates the SPLMETHOD system variable.

Object: Converts 2D or 3D quadratic or cubic spline-fit polylines to equivalent splines and (depending on the setting of the DELOBJ system variable) deletes the polylines.
Next Point: Enters additional curve segments until you press Enter.
Undo: Removes the last specified point.
Close: Closes the spline curve by defining the last point as coincident with the first and making it tangent to the joint.

Specify a point to define the tangent vector or use the Tangent and Perpendicular object snap modes to make the spline tangent or perpendicular to existing objects.

Options for Splines with Fit Points

Options specific to fit points are displayed when the Method option is set to Fit. (SPLMETHOD system variable)

Knots

Specifies the knot parameterization which affects the shape of the curve as it passes through a fit point. (SPLKNOTS system variable)

Chord - Numbers edit points with decimal values representing their location on the curve.
Square Root - Numbers edit points based on the square root of the chordal length between consecutive knots.
Uniform - Numbers edit points with consecutive integers.

Start Tangency

Creates splines based on tangent direction.

End Tangency

Stops creating curves based on tangent direction. You can continue creating spline curves by specifying fit points.

When you choose End Tangency, you are prompted for the last tangent of the last entered fit point.

Tolerance

Specifies the distance from specified fit points that the spline must pass through. Tolerance applies to all fit points except start and endpoints.

Options for Splines with Control Vertices

Options specific to control vertices are displayed when the Method option is set to CV. (SPLMETHOD system variable)

Degree: Sets the maximum number of “bends” you can get in each span; the degree can be 1, 2 or 3. There will be one more control vertex than the number of degrees, so a degree 3 spline has 4 control vertices.