NURBS – the state of the art.
Quite all the modern commercial CAD codes are general purpose and model 3D surfaces by means of NURBS (Non Uniform Rational B-Splines).
NURBS are defined with grids of control Points in a Cartesian coordinate system X, Y, Z (longitudinal position, offset and height). The slope and curvature of the resulting surface come out from the reciprocal position of these points.
These grids are usually defined acting interactively “by sight” on the screen. This mode is quick but coarse. The drawback is that a careful curvature fairing must follow every design session and this involves a problematic and patient work to tune (manually) the coordinates of the control points in the 3D space. To simplify the fairing work, it is often recommended to keep these grids as simple as possible by making use of few control points…
Moreover, many CAD systems allow only a linear surface scaling according the three Cartesian axis, with constant scale factors; the whole surface is so uniformly stretched or squeezed keeping unchanged the original curvature patterns. Automation systems or more sophisticated fine-tunings for the 3D model and generation of parent series are not supplied.
This technology, developed per high complexity applications, is tipically offered with a fully non-programmable manual interface.
As a result there are a number of limitations when is required a quick fine-tuning of simple 3D surfaces with high precision shapes. This is the case of the design of aerodynamic appendages and high performance racing hulls.
Lofter is different: complementary to traditional CAD systems, it is designed to exceed some their constraints.
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