Splines in sketches
The spline tools in the Sketch > Create panel let you create different types of splines as sketch geometry or construction geometry in an active sketch in Fusion.
A spline is a smooth, freeform curve that passes through or near a set of points that influence the shape of the curve. There are two kinds of splines in Fusion.
You can create open or closed splines.
You can use the following tools to create splines in an active sketch:
- Fit Point Spline
- Control Point Spline
to create a new sketch or right-click an existing sketch and select Edit Sketch to enter the Sketch contextual environment.Fit Point Spline
The Fit Point Spline tool creates a smooth curve that passes through a series of points.
Click to place the first point, place additional fit points, then click the Check icon 
to complete the spline.
Control Point Spline
The Control Point Spline tool creates a smooth curve driven by a control frame that you create by placing a series of points. Control Point Splines are also known as CV Splines.
Click to place the first point, place additional control points, then click the Check icon to complete the spline.
- A control point spline does not usually pass through the control points, except for the first and last points. In contrast to fit points, control points define the underlying frame used to calculate the curve.
- Control points apply tension to the spline in a given direction. If you pull a control point farther away, the tension on the curve increases in that area. If you push a control point closer, the tension relaxes.
- In most cases, you need more control points than fit points to define a given shape, because each control point has less influence on the overall curve than a fit point does.
- Control point splines do not offer tangent/curvature handles To apply more refined shape control, add more points.