Open Cascade Technology

Open Cascade Technology (OCCT), formerly called "CAS.CADE", is an open-source software development platform for 3D CAD, CAM, CAE, etc. that is developed and supported by Open Cascade SAS.
OCCT is a full-scale B-Rep (Boundary representation) modeling toolkit. OCCT is available under LGPL permitting its usage in open source and proprietary applications.
History.
"CAS.CADE" (abbreviated from Computer Aided Software for Computer Aided Design and Engineering) was originally developed in the early 1990s by Matra Datavision, developer of Euclid CAD software as the underlying infrastructure for its future version Euclid Quantum. In 1998 the company abandoned software development to concentrate on services, and most of the software development facilities were sold to Dassault Systèmes, developer of competing CATIA.
Open sourcing.
In 1999 Matra Datavision decided to publish its CAS.CADE infrastructure under an open-source model under the "Open CASCADE Technology Public License" and renamed it Open Cascade.
In 2000, a separate company, Open Cascade SAS, was created to make business around Open Cascade. Open Cascade SAS was sold in 2003 to Principia, a French service provider corporation, and then in 2006 it was acquired by Euriware Group, a subsidiary of Areva.
In 2004, software was renamed to Open Cascade Technology in order to distinguish it from the name of the company itself.
Open Cascade S.A.S. provides a certified version of the library, which is released sporadically, usually 1–2 releases per year. Until version 6.5.0 (2011), only minor and major versions were publicly available, while intermediate (maintenance) releases were accessible only to customers of Open Cascade S.A.S. For example, version 6.3.0 was publicly released in 2008, and the next public version 6.5.0 was released in early 2011. All recent releases starting from version 6.5.0 are public.
Community fork.
In March 2011, Thomas Paviot initiated a fork of the then most recent publicly available version 6.5.0 of Open Cascade library. The initiative is called Open Cascade Community Edition. The project aims to establish a separate community-based release and bug-report process for the library.
Collaborative development portal.
In December 2011, Open Cascade installed a web portal for external contributors and made its Mantis Bug Tracker and further Git repository publicly available (read-only GitHub mirror has been established in '2020). According to the statements on the new website, external contributors from the Open Source Community are encouraged to participate in the development of Open Cascade Technology, i.e. register bugs directly in the bugtracker, make contributions to the code after signing a Contributor License Agreement, etc.
License change.
Since 18 December 2013 with version 6.7.0 Open Cascade Technology is available under the LGPL 2.1 with additional exception. Versions before that were licensed under the "Open Cascade Technology Public License" which was not compatible with the GPL and was considered non-free by the Fedora project.
Functionality.
Object libraries.
OCCT's functionality is split into several large modules. Each module defines a list of toolkits (libraries). Key Modules:
Workshop Organization Kit.
Workshop Organization Kit (WOK) is Open Cascade development environment, which has been designed to allow a large number of developers to work on a product getting advantage of common reference version shared over the local network.
Until OCCT 7.0.0 release, substantial modifications in the source code were not possible without using WOK, since it is the only tool that provides support for CDL (CAS.CADE definition language), used for declaration of most of OCCT classes and also serving to define logical structure of OCCT libraries. WOK has been included in previous OCCT distributions; since OCCT version 6.4 it is made an independent tool.
Within 7.0.0 release, all CDL files have been dropped from OCCT source code making WOK no longer necessary for OCCT development.
CAD Programs based on Open Cascade Technology.
Several CAD programs relies on Open CASCADE Technology including:
CAD programs developed by Open Cascade itself relying on Open CASCADE Technology: