Project Overview

Open CASCADE Technology (OCCT) is an object-oriented C++ class library designed for rapid production of sophisticated domain-specific CAD/CAM/CAE applications.

A typical application developed using OCCT deals with two or three-dimensional (2D or 3D) geometric modeling in general-purpose or specialized Computer Aided Design (CAD) systems, manufacturing or analysis applications, simulation applications, or even illustration tools.

Key Advantages

Companies choose Open CASCADE Technology because of its strong competitive advantages over other CAD kernels.

No license fees

Software vendors choose Open CASCADE Technology because it can be used free of charge, and with no limitation as to the number of installed copies, meaning a greatly reduced cost of solutions based on it. Absence of license fees reduces costs of evaluation period, prototyping and piloting projects.

Access to source code

CAD/CAM/CAE software developers who need full control over the quality, stability and robustness of their applications choose Open CASCADE Technology because they can access its high-quality code. The users of Open CASCADE Technology can freely adapt, modify and enrich its source code by necessary functionality according to their particular needs.

Product continuity

Software vendors who care about the longevity of their products use Open CASCADE Technology because its permanent evolution and continuity are ensured by OPEN CASCADE, our industrial customers maintaining their own Open CASCADE Technology based solutions, and the worldwide community of Open CASCADE Technology users.


Companies, which pay significant attention to the quality of their software, develop with Open CASCADE Technology because its increasing quality and robustness is ensured by the Initial Developer (OPEN CASCADE). A large community of industrial users and customers are constantly testing the software thus helping OPEN CASCADE maintain a high level of quality and robustness of Open CASCADE Technology.

Openness and interoperability

Software vendors requiring their products to provide easy connection with other CAD/CAM/CAE software used by their customers prefer Open CASCADE Technology because it provides wide data exchange possibilities, both through neutral formats and directly with CAD systems. This enables an open, long-term viability of the solutions based thereupon. Learn more about the companies that have already chosen Open CASCADE Technology to empower their projects on a page dedicated to Our Customers.

OCCT library is designed to be truly modular and extensible, providing C++ classes for:

  • Basic data structures (geometric modeling, visualization, interactive selection and application specific services)
  • Modeling algorithms
  • Working with mesh (faceted) data
  • Data interoperability with neutral formats (IGES, STEP)

The C++ classes and other types are grouped into packages. Packages are organized into toolkits (libraries), to which you can link your application. Finally, toolkits are grouped into seven modules.
This modular structure is illustrated in the diagram below.

  • Foundation Classes module underlies all other OCCT classes
  • Modeling Data module supplies data structures to represent 2D and 3D geometric primitives and their compositions into CAD models
  • Modeling Algorithms module contains a vast range of geometrical and topological algorithms
  • Mesh module implements tessellated representations of objects
  • Visualization module provides complex mechanisms for graphical data representation
  • Data Exchange module inter-operates with popular data formats and relies on Shape Healing to improve compatibility between CAD software of different vendors
  • Application Framework module offers ready-to-use solutions for handling application-specific data (user attributes) and commonly used functionality (save/restore, undo/redo, copy/paste, tracking CAD modifications, etc.).

In addition, Open CASCADE Test Harness, also called Draw, provides an entry point to the library and can be used as a testing tool for its modules.


OCCT3D Open-Source Core Project Organization

Product Owner

The Project Leader drives the opening of development of the OCCT3D Open-Source Core product. He is responsible for all that relates to the organization of the project and the elaboration of the road-map.
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Technical Leader

The Technical Leader leads the development team that implements the collaborative work tools and methodologies. He is responsible for all that relates to the technical solutions proposed on this development website.
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Project Manager

Plays the lead role in planning, executing, monitoring, controlling, releasing activities. Inspires a sense of shared purpose within the project team, ensure everyone remains informed, motivated, happy and on board.
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Community Manager

Community Manager works on project promotion, partnerships and communication.
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The present project would not exist without the tremendous work done by the former MATRA DATAVISION development team, including the Architect of the main OCCT data structures (the so called Shape and Data Framework), the Designer of OCAF, the Modeling team who developed most of Geometry and Topology algorithms as well as the Topological Naming, the Designer of Data Exchange services, the Graphic team as well as the team in charge of the Kernel toolkit and development tools such as CDL, WOK and Draw. We are also grateful to the management who supported this project and decided to go to the open source.