Solid Modeling Solutions: Difference between revisions

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NURBS ([[Nonnon-uniform rational B-spline]]), 3D geometry, and [[Solidsolid modeling]] technology emerged in the 1980s and 1990s into a commercial implementation known as SMLib (for solid modeling library). This article will provide the background and history of this implementation into a commercial product line from [http://www.smlib.com Solid Modeling Solutions]™ (SMS). SMS is an independent supplier of source code for a suite of 3D geometry kernels. SMS provides advanced NURBS-based geometry libraries, SMLib™, TSNLib™, GSNLib™, NLib™, SDLib™, VSLib™, and PolyMLib™, that encompass extensive definition and manipulation of NURBS curves and surfaces with the latest fully functional non-manifold topology.

VSLib™ provides deformable modeling as part of a library using the constrained optimization techniques of the calculus of variations. The library supports several very different geometric operations.

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Once there was a reasonably good understanding of rational Bezier and non-uniform splines, we still had to put them together. Up to this point, the staff had not written or seen the form

: <math> P(t) = \frac{\sum_i w_i P_i b_i (t)}{ \sum_i w_i b_i (t) }

<!-- : P(t) = ∑iwiPibi(t) / ∑iwibi(t) -->

for anything more than a conic Bezier segment. Searching for a single form, the group worked together, learning about knots, multiple knots and how nicely Bezier segments, especially the conics, could be imbedded into a B-spline curve with multiple knots. Looking back, it seemed so simple: It is easy to verify that the equation for P(t) is valid for the B-spline basis functions as well as for Bernstein basis functions. By the end of 1980 the staff knew we had a way to present all the required curve forms using a single representation, now know as the NURBS form. But this new representation could easily have died at this point. The staff were already 12 to 18 months down a development path. They had completed a large number of algorithms using the old curve forms. They now had to convince our managers and the other technical groups, such as the database and graphics groups, that they should be allowed to start over using a single representation for all curves. The NURBS surface form did not present a problem since they had not yet developed any surface algorithms. The review of this new TIGER curve form was held on February 13, 1981. The review was successful and the staff were allowed to start over using the new curve form. It was at this time that the NURBS acronym was first used by the other side of the TIGER project, i.e., the TIGER software development groups of Boeing Computer Services. Management was very eager to promote the use of these new curve and surface forms. They had a limited understanding of the mathematics but they were very aware of the need to communicate geometric data between systems. Hence, Boeing very quickly prepared to propose NURBS to the August ’81 [[IGES]] meetings. Richard Fuhr, of our group, was assigned the job of presenting NURBS to IGES. His presentation was very well received and shortly afterwards he put together the Boeing document which was distributed to many IGES members.

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For reviews of geometry kernels shortly after the first release of SMLib, see Joe Greco's article "Kernel Wars - Episode 1"<ref>"Kernel Wars - Episode 1", Joe Greco, CADENCE magazine, November 1999</ref> and Don LaCourse's article on Geometric Modeling Kernels Revisited".<ref>"Geometric Modeling Kernels Revisited", Don LaCourse, Cadalyst magazine, April 2001</ref> Also, see a recent review of PolyMLib in Desktop Engineering, Nov 2008.<ref>"Polygonal Mesh Library for Postprocessing 3D Scan Data", Desktop Engineering, Nov 2008</ref>

==SMS Architecturearchitecture==

SMLib™ - fully functional non-manifold topological structure and

solid modeling functionality.