Open CASCADE Technology (OCCT)

Open CASCADE Technology (OCCT, often written OpenCascade) is a free, open-source C++ geometry kernel for 3D solid and surface modeling, CAD data exchange and visualisation, used by software developers who build CAD, CAM and CAE applications. It is the modeling engine behind FreeCAD and many engineering tools. An OpenCascade download today means version 8.0.1, released on 30 July 2026 by Open Cascade SAS.

To be clear about the dental angle: OCCT has no dental features, and there is no “dental edition” or dental CAD module. It will not design a crown, plan an implant or generate an aligner. It is relevant to dentistry only for developers and technically minded labs building their own tools, for example to convert engineering CAD files, generate parametric parts or embed STEP and STL handling in a custom application.

Open CASCADE Technology at a glance

What it does

• Foundation Classes: basic types, collections and memory management for the rest of the kernel.
• Modeling Data and Modeling Algorithms: boundary-representation (B-rep) solids and surfaces, Boolean operations, sweeps, fillets and chamfers.
• Mesh: tessellation of exact geometry into triangles for display or STL export.
• Visualization: OpenGL-based 3D display with interactive selection and ray tracing.
• Data Exchange: STEP (AP203, AP214, AP242), IGES up to 5.3, glTF 2.0, OBJ, VRML and STL.
• Application Framework (OCAF): documents with undo/redo, attributes and persistence.
• Draw Test Harness: a Tcl-based console with 2D/3D viewers for trying algorithms without writing a full application.

How dental teams use it

These are general CAD tasks. They suit developers or labs with in-house programming skills; they are not dental features of OCCT.

Convert a STEP file to STL for printing

1. Read the STEP file with OCCT’s STEP reader (or open it in Open Cascade’s free CAD Assistant viewer, which is built on OCCT).
2. Tessellate the shape with the incremental mesher, choosing a deflection small enough for your printer’s resolution.
3. Write the result with the STL writer and check the mesh in your slicer or dental CAD software.

Generate parametric lab parts in code

1. Build primitive solids (boxes, cylinders) with the primitive API and combine them with Boolean fuse and cut.
2. Round edges with fillets and expose the dimensions as parameters.
3. Export each variant to STEP for machining or STL for printing, and validate it before use.

Use an OCCT-based application instead of code

1. Install FreeCAD, whose geometry kernel is OCCT.
2. Model engineering-style items such as holders or jigs with its part and sketch tools.
3. Export to STL; for organic shapes such as teeth, stay with mesh-based dental CAD.

Install and first run

• Binaries and source: the official site and GitHub release pages publish source archives and platform packages with the third-party libraries included.
• Building from source: use CMake with a supported compiler on Windows, Linux or macOS; the official documentation for 8.0 lists third-party dependencies and build options.
• Python: OCCT itself is C++, but third-party bindings exist, such as pythonOCC and OCP (the bindings used by CadQuery, published on PyPI as cadquery-ocp with 8.0.1 builds).
• First test: start the Draw Test Harness, load a sample shape and display it to confirm that the build and graphics driver work.
• Gotchas: version 8.0 is a major release, so code or bindings written for 7.x may need changes; check that any wrapper you use supports the OCCT version you installed.

Limitations

• No dental functions: no tooth libraries, margin lines, crown, implant or aligner design.
• A developer library, not an end-user CAD program; you need C++ (or a wrapper) and CAD knowledge.
• Designed for exact B-rep geometry. Intraoral and model scans are triangle meshes: OCCT can import STL, but a scan stays a triangulation rather than editable surfaces, and mesh-first tools handle such data better.
• Some exchange formats and advanced tools are sold as commercial add-ons.
• Anything you build for patient use needs your own validation; OCCT carries no medical certification.

Open CASCADE Technology vs alternatives

Commercial kernels such as Parasolid are used in major CAD products but are not open source. CGAL is an open-source C++ library focused on computational geometry and meshes rather than B-rep CAD. FreeCAD is not an alternative so much as an application built on OCCT. For triangle-mesh work closer to dental scans, OpenFlipper is a mesh-processing framework, and VTK handles STL/PLY display and mesh filters. If you only need to look at a STEP or STL file, a viewer such as CAD Assistant is simpler than the kernel.

FAQ

Is OpenCascade free to download?

Yes. OCCT is free and open source under LGPL 2.1 with an additional exception, and it can be used in commercial applications. Some add-on components from Open Cascade are commercial.

Is there an OpenCascade download for Windows and Linux?

Yes. Version 8.0.1 supports Windows and Linux on x86-64, as well as macOS, Android, iOS and the web.

How do I use OpenCascade from Python?

Through third-party bindings: pythonOCC or OCP, which CadQuery uses. Check that the binding matches your OCCT version.

What is OpenCascade CAD Assistant?

CAD Assistant is Open Cascade’s free viewer and converter for STEP, IGES, STL, OBJ, glTF and other formats, built on OCCT and free for personal and commercial use.

OpenCascade vs Parasolid: what is the difference?

Both are B-rep geometry kernels. OCCT is open source under LGPL; Parasolid is a proprietary commercial kernel.

OpenCascade vs FreeCAD?

OCCT is the geometry kernel; FreeCAD is a full parametric CAD application that uses OCCT underneath.

Can OpenCascade be used for dental CAD?

Only as a building block. It has no dental tools; developers can use it for STEP/STL conversion and parametric parts inside their own dental software.

Last checked against official sources: 29 September 2026 (developer website: occt3d.com). Versions and licence terms change — confirm on the developer's site before deploying in a clinic.