Open CASCADE Technology consists of C++ classes grouped into Packages. They are organized into Toolkits (libraries), and the latest are grouped into seven Modules. You can download Open CASCADE library totally free and use it at any PC with Windows, macOS or Linux. Please refer to our Download page for easy OCCT access. If you are interested in OCCT open-source code, go to the Git Repository for simple git access without registration.


Geometric modeling

OCCT algorithms allow to:

  • Calculate the intersection of two 2D curves,
    surfaces, or a 3D curve and a surface
  • Project points onto 2D and 3D curves,
    points onto surfaces, and 3D curves
    onto surfaces
  • Construct lines and circles from
  • Construct curves and surface
    from constraints
  • Construct curves and surfaces
    by interpolation and

Geometric modeling

Surface and solid modeling

OCCT comes with algorithms for:

  • Construction of primitives (box, sphere, cylinder, cone, torus, wedge)
  • Computation and comparison of distances between shapes
  • Construction of prisms and pipes
  • Surface extrusion/revolution
  • Defining offset surfaces/curves
  • Defining fillets and chamfers
  • Boolean operations (input, common, cut, fuse.)

Surface and solid modeling

Data Exchange

Data Exchange module allows developing OCCT-based applications that interact with other CAD systems by writing and reading 3D models to and from external data in open and vendor-neutral formats.

This tool handles various problems of interoperability between CAD systems, caused by differences in model validity criteria and requirements to internal representation.

Supported formats:

B-Rep: STEP (ISO 10303), IGES, BREP (native)
Mesh: glTF, VRML (ISO 14772), OBJ Wavefront, STL


OCCT visualization toolset provides:

  • Cross-platform renderer based on OpenGL and OpenGL ES
  • Compatibility with mobile, embedded (OpenGL ES)
    and web (WebGL) platforms
  • Built-in photo-realistic Ray-Tracing engine
    supporting global illumination
  • Clipping planes/box with capping
  • PBR metallic-roughness
    material workflow
  • Fast algorithms picking
    objects by mouse


Should you have more particular queries (for example, how to read dwg files in OCCT or what is the easiest free cad drawing software to use for your specific purposes etc.), one of the ways you can get support is reading blog or posting on OCCT forum, where all the questions are very welcome.

Active forum topics

New forum topics

Use cases

Open CASCADE Technology is also a backbone of many good projects. For example, FreeCAD providing parametric 3D modelling, drafting and many other capabilities is easy to use for beginners. KiCad – free 3D CAD software for PCB layouts design. Gmsh – a fast meshing tool. Salome – a platform for numerical simulation. CAD Assistant – a powerful viewer and converter.
Visit OCCT Projects & Products Marketplace to learn more.


OCCT in Research & Science

Open CASCADE Technology (OCCT) is actively used at an academic and research levels around the globe. OCCT Research and Science website section presents more than 600 articles and research projects conducted by 400+ organizations in 48 countries. Browse by subject, author, or country to get a wider look at OCCT capabilities and application opportunities. Explore the collection of research publications via the link.

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