The Spline Command

Toolbar	Draw
Pull-down	DrawSpline
Keyboard	SPLINE	short-cut	SPL

The Spline command creates a type of spline known as a nonuniform rational B-spline, NURBS for short. A spline is a smooth curve that is fitted along a number of control points. The Fit Tolerance option can be used to control how closely the spline conforms to the control points. A low tolerance value causes the spline to form close to the control points. A tolerance of 0 (zero) forces the spline to pass through the control points. The illustration on the right shows the effect of different tolerance values on a spline that is defined using the same four control points, P1, P2, P3 and P4.

Splines can be edited after they have been created using the SPLINEDIT command, ModifyObjectSpline from the pull-down menu. Using this command, you can change the tolerance, add more control points move control points and close splines, amongst other things. However, if you just want to move spline control points, it is best to use grips. See the Stretching with Grips section of the Modifying Objects tutorial for details.

Command Sequence

Command: SPLINE
Specify first point or [Object]: (Pick P1)
Specify next point: (Pick P2)
Specify next point or [Close/Fit tolerance] : (Pick P3)
Specify next point or [Close/Fit tolerance] : (Pick P4)
Specify next point or [Close/Fit tolerance] :
Specify start tangent: (pick a point)
Specify end tangent: (pick a point)

You can create linear approximations to splines by smoothing polylines with the PEDIT command, ModifyPolyline from the pull-down menu. However, you can also turn polylines into true splines using the Object option of the Spline command