Sketcher BSplineDecreaseDegree/de

Beschreibung
Verringert den Grad (die Ordnung) des B-Spline.

B-Splines sind im Grunde eine Kombination aus Bézier-Kurven (sehr schön erklärt in dies und dieses Video).

In diesem kubischen Spline (Grad 3) gibt es 3 Segmente, d.h. 3 Kurven sind an 2 Knoten verbunden (der Grad wird durch die Zahl angezeigt, die Anzeige kann über die Schaltfläche in der Werkzeugleiste geändert werden ):



The outer segments have each 2 control points, the inner one none to fulfill the constraint that the knots have multiplicity 1. (see this page for an explanation of the multiplicity)

Decreasing the degree will not delete control points but try instead to conserve the shape of the spline. Therefore segments will be added. For our example you see a lot of new spline segments with each one control point and the shape of the spline has only slightly been changed:



If you take this result and increase the degree, you cannot get the initial state of the spline because information was lost by the prior decrease of the degree. For our example increasing the degree again leads to this:



Anwendung

 * 1) Select an edge from an existing B-spline, and press.