Example: Spline Surface Data Format
The parametric spline surface is a nonuniform bicubic spline surface which passes through a grid with tangent vectors given at each point. The grid is curvilinear in uv space.
The tan_cond field, which represents the tangency of the spline surface in the Neutral file format, is an array of two integers. A value of 4 in the tan_cond field indicates that the spline surface is periodic in the given direction. Any other integer value indicates that the spline surface is nonperiodic in the given direction.
A cylindrical spline surface includes a spline surface in its definition.
The following illustration shows a spline surface.
Data format:
u_par_arr[] | Point parameters, in the u direction, of size Nu |
v_par_arr[] | Point parameters, in the v direction, of size Nv |
point_arr[][3] | Array of interpolant points, of size Nu & Nv |
u_tan_arr[][3] | Array of u tangent vectors at interpolant points, of size Nu & Nv |
v_tan_arr[][3] | Array of v tangent vectors at interpolant points, of size Nu & Nv |
uvder_arr[][3] | Array of mixed derivatives at interpolant points, of size Nu & Nv |
Parameterization:
• Allows for a unique 3 & 3 polynomial around every patch.
• There is second-order continuity across patch boundaries.
