Pythagorean-Hodograph B-Spline Curves
This work provides a new mathematical tool for practitioners in computer-aided design and manufacturing, robotics, and animation who need curves with exact arc-length and rational offsets.
The paper introduces Pythagorean-Hodograph (PH) B-Spline curves, a new class of planar parametric curves that generalize PH Bézier curves, with the property that their arc-length is a B-Spline function and their offsets are NURBS curves. This offers advantages for CAD/CAM, robotics, and related fields.
We introduce the new class of planar Pythagorean-Hodograph (PH) B-Spline curves. They can be seen as a generalization of the well-known class of planar Pythagorean-Hodograph (PH) Bézier curves, presented by R. Farouki and T. Sakkalis in 1990, including the latter ones as special cases. Pythagorean-Hodograph B-Spline curves are non-uniform parametric B-Spline curves whose arc-length is a B-Spline function as well. An important consequence of this special property is that the offsets of Pythagorean-Hodograph B-Spline curves are non-uniform rational B-Spline (NURBS) curves. Thus, although Pythagorean-Hodograph B-Spline curves have fewer degrees of freedom than general B-Spline curves of the same degree, they offer unique advantages for computer-aided design and manufacturing, robotics, motion control, path planning, computer graphics, animation, and related fields. After providing a general definition for this new class of planar parametric curves, we present useful formulae for their construction, discuss their remarkable attractive properties and give some examples of their practical use.