B-Splines by interpolation

See also: Splines by control points, Bezier Splines, B-Spline from scattered points, Convert into b-spline.

Menu access : Curves | Splines

Description:

Allows you to create curves going through points you define.

General philosophy:

1. Choose INTERPOLATION in the list

2. Select the starting point of the curve.

3. Select the passing points.

4. Use the  STOP WITH NULL CURVATURE  button when you have selected the last point.

Available Option(s) :

Tangency:

The button  START TANGENT  (for the beginning of the curve) or  TANGENT   (for the other points) allows you to set tangency using lines or points.

The option  Tangent on curve extremity = YES   or  NO  allows to define if the spline is hooked to the extremity of the selected curve or on the curve at the selected point.

The more the tangency point is far from the b-spline point, the more the tangent is pronounced. You can modify the tangency point afterwards using the "Move parents" function.

When defining a tangency on a point of the b-spline, the button  DIRECTION  allows you to use an axis or line as direction for the tangent.

Once the length of the tangent has been defined dynamically, the option  Length=......    allows you to  define a more specific value for the tangency length.

The option  Mode= OPEN  or  CLOSED  allows you to choose the curve type you want to get. An open curve has distinct extremities. While a close curve has no extremities (you cannot start or end with tangent); the first and last points are automatically linked.

Example(s):

Specific point(s):

You can select several time the same point to "overload" a point.

Thanks to the function "Edit | Insert", you can dynamically insert a knot or a point into a basic b-spline.

•  Insert= POINT  allows to insert a new point and modify the b-spline geometry.

•  Insert= KNOT  allows to insert a new point without modifying the actual b-spline geometry.

Available modification(s):

The icon allows you to

• show or hide the control polygon of the curve or the tangents.

• modify the parameter of a tangent.

• add or remove a tangent on a passing point.

• Separate or link up the two tangents of a passing point. Once the tangents separated, you can move them independently by using the icon . In the above illustration, tangents on the right end extremum have been  separated.

The icon allows you to move a point of the curve or the curve itself.