Geometry Comparison software deals with the problem of detecting differences in 3D models within a specified tolerance.

LEDAS developed its Geometry Comparison technology to check and locate all of the differences between similar-looking geometric models. These changes can come about through:

- revisions made to a model
- from files generated by different CAD systems of the same model
- the result of polygon and NURBS representations of the same geometry
- data generated by various steps in the processing of 3D geometry.

When comparing two similar-looking 3D models, it is essential to distinguish between differences that are important and defects that are negligible. So this makes 3D model comparisons very different from a simple text comparison, where only text that is fully identical is considered as having no difference.

Making comparisons between 3D geometry requires operations performed at the most basic levels, and so are usually provided by 3D modeling kernels, of which C3D is an example. Geometry comparison is a component technology powered by C3D, and so this integration expands C3D’s sphere of application. The kernel is now being marketed as a general purpose tool for any engineering software needing advanced 3D modeling.

Until now, geometry comparison has been mostly done through Boolean subtraction operations, which is a core function of geometric kernels, such as Parasolid and ACIS. The difference between 3D bodies is found by subtracting the volume of one body from another.

3D geometry consists of two levels of geometry representation: topology (made of faces, edges, vertices), and underlying geometry (surfaces and curves that define the form of faces and edges). It is relatively easy to map topology of one 3D model to the topology of another model: each entity gets its counterpart, and if mapping for some entities does not exist, then the difference is found at the topological level. It is more complicated to find difference (or to check that there are no differences) when taking into account underlying geometry and specified tolerances. The solution developed by LEDAS makes it possible to detect differences at both the topological and geometric levels.

For those of us who have grown up with and seen the CAD industry evolve, it means experiencing CAD from a relatively narrow perspective, that is, a US perspective. As it turns out, the CAD development realm actually extends far beyond our shores, and is becoming more competitive over time. Some of the most noteworthy competitors are coming from Russia.

One of the more interesting CAD tools I’ve come across in the past few years is from Russia — ASCON’s KOMPAS-3D for associative 3D modeling. Models can be made from original designs, standard part libraries, or combination if the two. While that’s not especially unique, KOMPAS-3D’s parametric technology lets you generate ranges (different configurations) of products based on a single source model.

A distinguishing feature of KOMPAS-3D is that it uses its own modeling kernel and parametric system, both of which were developed at ASCON — something I have always considered an advantage over licensing components that form the basis of a CAD product.

The following video clip provides a brief overview of the KOMPAS 3D geometric modeling kernel:

**KOMPAS 3D Modeling Kernel
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What the video lacks in detail introduces the possibility that ASCON and its 3D modeling kernel could increasingly become a power to be reckoned with in the future.

A couple of years ago ASCON Group made public its proprietary geometry kernel, C3D, as the foundation for creating CAD systems and applications.

Development of the C3D kernel began in 1995, and became the basis for ASCON’s KOMPAS-3D in 2000. The company continued to update the kernel, and last year launched it as a separate product for the CAD component market. It can handle several aspects of a CAD system, icluding 2D drawing and sketching, 3D hybrid and solid modeling, parametric constraints, and translation.

The main feature of ASCON kernel is that it is comprehensive. The core of C3D combines just about everything necessary for developing engineering application software with modules that include:

- C3D Modeler — the geometric modeler with functions for 3D solid and hybrid modeling, sketching, and 2D drawing.
- C3D Solver — the parametric constraints solver with functions for creating and solving parametric constraints on 2D and 3D geometry.
- C3D Converter — the translator module that reads and writes geometric models in all primary exchange formats.

Keep in mind, though, that the C3D kernel is not the only Russian kernel being developed there. There is also a Russian government-financed mandate to develop a “national” CAD engine, the Russian Geometry Kernel (RGK), a B-rep modeler that can create NURBS curves and surfaces. The RGK is being developed by Russian university mathematicians, and like the C3D modeler, it supports GPU acceleration and multi-threading.

The ultimate winner of the Russian kernel competition is anybody’s guess, but ASCON seems to have a number of technical things in place to make it a real player in the worldwide CAD arena. To a large extent, because it’s in control of its base product components, it may have better control over its destiny in a competitive market.

“We first became familiar with C3D when we began a joint project with ASCON aimed at integrating our LEDAS VDM (Variational Direct Modeling) technology into C3D and KOMPAS-3D,” said Ivan Rykov, CTO of LEDAS. “Our long experience in developing and using 3D modeling software makes it possible for us to easily identify the advantages and bottlenecks of any 3D modeling kernel. C3D made a really positive impression on us while we were testing it in our Geometric Comparison project, especially with regards to its stability and with the technical support from ASCON.”

“C3D is constantly increasing its portfolio of customers,” said Oleg Zykov, CEO of C3D Labs, an ASCON subsidiary and the developer of C3D. “For the first few years, we focused on the Russian market, but now our goal for 2014 is to increase sales to the international market. Because LEDAS is well-known internationally, we consider the integration C3D with their technology as a good step in this direction.”

So, it just might be true for the CAD arena, “The Russians are coming.”

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