MANIPULACIÓN DE A-SPLINES CÚBICOS BASADA EN RESTRICCIONES

Abstract

In geometric modeling or graphic design applications the interactive manipulation of geometric properties, such as position, tangency and curvature is crucial. Qupting [12], the conventional methods do not provide direct control at arbitrary points on the curve. Users may have some control at a few specific points and this control strongly depends on the representation of the curve. For instance, Bezier curves offer direct representational control of position and tangency at the endpoints of its sections, but not at its interior points. Users control
properties on the interior of the curves indirectly by manipulating the control vertices or by complicating the curves through subdivisions. In this work, we introduce methods to provide a more direct and intuitive control of a cubic A-spline curve: the first method permits to assign a tangent direction to a prescribed interior point, while the second assigns a prescribed line as the tangent line at some interior point. These are basic tasks in the constraint-based curve manipulation and in the present work we demonstrate that they may be efficiently solved
using cubic A-spline curves.