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NEWSLETTERS:

The January/February issue of IEEE Computer Graphics and Applications named SMLibTM to their Top 10 Software of 1998. John Dill said in his article, "Choosing only 10 products gets harder and harder, as the products open up new areas, specialize, and form new combinations." One of the SMLibTM customers has seconded the award by saying " SMLibTM is certainly one of my Top 10 products."

Solid Modeling Solutions in conjunction with HarmonyWare, Inc. announces the general availability of IGES/SMLib, its new capability to translate IGES formats into and out of SMLibTM. Details on IGES/SMLib can be found on the web at www.harmonyware.com.

IGES/SMLib allows reading and writing of IGES files, interfacing with the Nlib and TSLib kernels of SMLibTM. Its major features include:

• Resistance to faults in the physical format of the IGES file.
• Reads most IGES geometry entities.
• Imports and exports points, curves, surfaces, and trimmed surfaces; imports solid faces as unconnected trimmed surfaces.
• Trimmed surface types 142/144, 141/143, and 508/510 supported.
• Sophisticated cleaning tools: eliminating minor self-intersections and gaps in trim loops, improving singularities, etc.
• Supports conversions of IwBrep entities to and from IGES trimmed surfaces.
• Simple high level interfaces, plus full access to the powerful under-the-hood classes used to implement them.

The translator is available as C++ source code, designed with the new ISO C++ standard in mind, but targeted at the prior generation of compilers.

Solid Modeling Solutions had a booth recently at the MICAD show in Paris, France during the exhibit from February 9 ñ 12. Solid Modeling Solutions and IntegrityWare will be sharing a booth at the Westec '99 show in Los Angeles Convention Center. See us in booth #5947 from March 22 ñ 25. We have also committed to a booth at the MTECH/West show in the Los Angeles Convention Center from May 25 ñ 27, SIGGRAPH 99 in Los Angeles from August 10 ñ 12, and the MTECH show in Chicago's McCormick Place from November 10 ñ 12. More details will be provided on our website at www.smlib.com.

Our underlying assumption is that we cannot possibly satisfy everyone's filleting, chamfering and blending requirements. We have seen teams of 4-6 programmers working full time on filleting for years at major CAD companies and still have not satisfied all of their user requirements in all application areas.

Our basic plan is to offer 50%-75% of the functionality of something like Parasolid or ACIS combined with an Object-Oriented Framework where the users of SMLibTM can easily plug in additional functionality with minimal effort. Here is how we will accomplish this:

We are implementing a framework which handles basic topological cases and has a reasonable set of geometric cases. The framework will handle most of the bookkeeping tasks and will have object-oriented difficult condition handlers. For example, what does one do if the fillet rolls off the edge of a surface or if the fillet rails self intersect. We will implement a basic set of default difficult handlers. The end users can then change the default behavior by implementing a subclass of the particular handler. For example, if the fillet rolls off the surface, the user might want to cut the fillet, roll a ball along the edge, roll the fillet over onto the adjacent surface, just quit, etc.

The generation of fillet geometry has two major parts which can be modified - the way the rails are generated and the geometry used to create the cross sections. The user will also be able to pass into the fillet module existing surface geometry to be used during the filleting operation. For example, he may want some sort of fancy blend between two surfaces to be used as the fillet surface for a given edge. We would simply take the geometry instead of trying to generate it from scratch. So far we have implemented the following three rail tracing methods:

• Constant radius fillet
• Constant distance and angle between surface
• Variable radius fillet using a Law function

We have also implemented the following three cross section geometry types:

• Circular - rational
• Circular with a non-rational approximation
• Linear

We can now generate fillets with any combination of the above rail generation techniques and cross section geometries.

Perhaps the most difficult part of this whole problem is the handling of different corner cases based on the type of edge being filleted and the radii of the fillets entering a vertex. We will implement perhaps 20 different corner cases and have a default mechanism for blending corners using the N-sided patch from NLib. This is probably an area where much customization would occur based on the target applications (i.e. plastics, auto body design, sheet metal, etc.). They should be able to implement new corner cases in one or two days.

At some point we will add analytic fillet surface cases (torus, cylinder, cone, etc.) and analytical corners (sphere, torus) to improve accuracy and down stream reliability.

We will augment our surface definitions with implicit fillet information to capture the fact that a surface was generated from a blending operation. This is useful for refining the surface when operations like Booleans occur. If a fillet is cut, we would insert additional knots into it to make the vertices very accurate.

We will use the powerful solver capability in GSLib to solve for exact edge/rail and rail/rail intersections prior to the generation of the fillet surface. This will ensure that we generate only the portions of the fillet that we need and that they are exact at the topological vertices when initially created.

We hope this gives you a better understanding of how the SMLibTM licensees will be able to use the SMLibTM filleting so as to satisfy the needs of many different end users.

In the next SMLib Newsletter issue we will be presenting an "SMLib Market Position White Paper". This paper will discuss SMLib's position in the market and illustrate how you can best take advantage of SMLib's unique capabilities and pricing.