Insert
Curve Interpolation Points
The New curve Mode of the Curve through Interpolation Points command enables you to create a new spline curve by specifying its interpolation points.
The points to be interpolated can be specified either by entering them directly in the document, or by reading them in an ASCII file (extension ".pt"; each line in the file must contain the coordinates of a point in the world coordinate system; each coordinate is separated by the following through a blank character). The input mode can be chosen in the From drop-down list:
| Points | To enter points by specifying them directly in the document, by clicking or using the snap commands. |
| ASCII file | To read the points in an ASCII file that can be selected in an ordinary file selection box by clicking Browse. |
By default, the curves created using this command are NURBS curves with degree = 3 and continuity = 2 (ordinary cubic splines). In order to provide smoother continuity at each interpolation point, it is possible to create also quintic and septic curves (degree=5 or 7). This is a great benefit when modifying the curve by editing its control points, as the curvature plots will remain smooth.
The Degree drop-down list under More Options enables you to choose 3 to create an ordinary cubic spline, 5 to create a quintic curve or 7 to create a septic curve when you need smoother continuity at the interpolation points.
The curve shape can be controlled using the options of the Rule drop-down list.
While this command is active, you can start the Curvature command (either from the menu bar or from the context menu). This will start the curvature analysis on the curve and the result will be displayed as a curvature plot on the curve being created/modified. You will also get the Curvature related options in the selection list.
| Associativity If you select the Associative Mode — see the "Associativity" section of "An Overview on Curves" — check box in the selection list and enter points by snapping to special points of existing entities in the model, an associativity link will be retained between the created point and the special point you snapped to. If the position of the special point changes, the position of the point you created will change as well and the curve shape will be modified accordingly. The Curve through Control Points does not apply to associative curves created using this method. |