Hermitian B-splines

This paper proposes to study a spline model, called HB-splines, that is in fact a B-spline representation of Het mite splines, combined with some rest riction on the differential values at segment boundaries. Although this mod el does not appear able to offer something new to the computer graphics com munity, we think that HB-splines deserve to be considered for themselves be cause they embed many interesting features. First, they include all the cla ssical properties required in a geometric modeling environment (convex hull , local control, arbitrary orders of parametric or geometric continuity). S econd, they have a nice aptitude for direct manipulation (i.e. manipulation without using control points). For this purpose, we propose a new graphic widget, called control sails, that offers the user an intuitive way to spec ify local properties (position, tangent, curvature) of a curve ol a surface . Finally, they provide an elegant formulation of a biorthogonal wavelet fa mily, that permits multiresolution manipulations of the resulting curves or surfaces, in a very efficient way.