Insert Spline Graphically

Enters a Spline graphically using the mouse by specifying Points on the Spline.

A spline is a set of more than 2 points connected smoothly by cubic arcs. HYDRUS allows three types of splines:

• cubic spline, i.e., a curve defined by multiple polynomials of the third order. It passes smoothly through all points.
• Bezier’s curve – a smooth curve that passes through boundary points, but does not have to pass through internal points .
• B-spline – a general Bezier’s curve.

More information can be found at:

http://mathworld.wolfram.com/BezierCurve.html

http://mathworld.wolfram.com/B-Spline.html

Once a command for defining a new spline graphically is selected, a cursor in the View Window will become a cross with a small empty circle in the middle. The coordinates of the location of the cursor will be displayed next to the cursor and on the Edit Bar, which will automatically change to the one displayed below. The Edit Bar will also show, which point and curve (their numbers) are being defined and what reference coordinate system (the current coordinate system, the grid origin, or the last inserted point) is used. One node is specified after the other. A user can also select on the Edit Bar the type of the spline (standard spline, B-spline, or Bezier curve). The process of defining a new spline is ended by pressing the Esc keyboard button, the right mouse button (see the Help part of the Edit Bar), or clicking the Stop button on the Edit Bar.