Geometry & modeling
CAD kernel
Definition
A CAD kernel is the geometry engine inside a CAD program that creates and modifies solids: booleans, fillets, shells, intersections, and tessellation for display. Parasolid and Open CASCADE are common examples, and the kernel largely decides which operations are reliable and how exports behave.
Also known as: geometric modeling kernel, geometry kernel, modeling kernel, solid modeling kernel
Updated
Shared kernels#
Many CAD programs license the same kernel. Siemens says its Parasolid kernel's XT format is compatible with more than 350 applications. Open CASCADE Technology is an open-source kernel used by FreeCAD, and CadQuery reaches it through Python bindings called OCP.
Why the kernel shows up in daily work#
Two programs on the same kernel usually exchange geometry more cleanly than two on different kernels, because they agree on tolerances and surface types. When a fillet fails or an imported part has gaps, the cause is often a kernel limit or a tolerance mismatch rather than the user's modeling. Text-to-CAD tools that output B-Rep also need a kernel, either licensed or built in-house, to turn generated operations into valid solids.
Sources
Related terms
B-Rep
B-Rep is the way professional CAD kernels describe a solid: by its boundary, made of exact surfaces (faces), the curves where they meet (edges), and the points where edges end (vertices). Because the geometry is exact and the topology is explicit, B-Rep models can be measured, filleted, dimensioned, and manufactured precisely.
CadQuery
CadQuery is an open-source Python library for building parametric CAD models in code on top of the Open CASCADE kernel. It can export STEP as well as STL and 3MF, which makes it a common target when LLMs are asked to write CAD scripts.
AI-native CAD
AI-native CAD describes CAD software designed with AI as a core part of how geometry is created and edited, rather than an assistant added to an existing product. It is a marketing term without a standard definition, so claims should be judged by what the software actually does.