The Hidden Core
An exploration of one of the most interesting topics in the CAD industry follows. This subject often goes unnoticed, as it represents a less visible layer of CAD software ecosystems. The following text examines the relationship between CAD vendors and modeling kernel developers.
It is difficult to build systems that are entirely self-contained from a technical perspective. Invisible layering is the true nature of large software systems. A development company can aim for full-stack control or remain partially dependent on an external, third-party kernel.
In simple terms, many CAD systems are built on top of a geometric modeling kernel that handles the core mathematical components: Boundary representation (B-rep) of geometry and topology, boolean operations, intersections, interpolations, approximations, etc. The CAD company builds the application's user interface (UI), user experience (UX), workflows, and higher-level features around the kernel.
Notable geometric modeling kernels include:
3D ACIS Modeler (ACIS) is a geometric modeling kernel developed by Spatial Corporation, a division of Dassault Systèmes.
Convergence Geometric Modeler (CGM) is the proprietary geometric modeling kernel developed by Dassault Systèmes.
Parasolid is a geometric modeling kernel owned and developed by Siemens.
Open CASCADE Technology (OCCT) is a world-known 3D modeling kernel, freely available as open source.
Rhinoceros 3D (by Robert McNeel & Associates) implements its own NURBS-surface geometry kernel.
Autodesk ShapeManager is the solid modeling kernel used in AutoCAD-based products. It is derived from ACIS.
C3D kernel is a geometric modeling engine originally developed for KOMPAS-3D software. It was later established as an independent product under the C3D Labs.
What can we understand from this, and what does this relationship actually look like?
The modeling kernel is the engine of any CAD system, while the CAD application is the layer of high-level logic, command chains, and UI usability built on top of that engine. The CAD application inherits the limitations of the kernel.
Moreover, kernel licenses are expensive, and partners often sign revenue-sharing agreements. These costs are passed down to the end user, meaning your subscription fee supports both the usable application and the underlying kernel.