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-only 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: Foundation Classes: defines basic classes, memory allocators, OS abstraction layer, collections (data maps, arrays, etc.), acceleration data structures (BVH Trees) and vector/matrix math used by other Modules. Modeling Data: supplies data structures to represent 2D and 3D geometric primitives (analytical curves: Line, Circle, Ellipse, Hyperbola, Parabola, Bézier, B-spline, Offset; analytical surfaces: Plane, Cylinder, Cone, Sphere, Torus, Bézier, B-spline, Revolution, Extrusion, Offset) and their compositions into B-Rep models. Modeling Algorithms: contains a vast range of geometrical and topological algorithms (intersection, Boolean operations, surface meshing, fillets, shape healing). Visualization: provides interactive services for displaying geometry in 3D Viewer; implements a compact OpenGL / OpenGL ES renderer, supporting conventional Phong, real-time PBR metal-roughness shading models as well as interactive Ray-Tracing/Path-Tracing engine. Data Exchange: provides possibility to import/export various CAD formats. STEP, IGES, glTF, OBJ, STL and VRML are supported natively. Other formats can be imported by using plug-ins. Extended Data Exchange (XDE) components rely on a unified XCAF document definition, which includes an assembly structure of CAD shapes, color/name/material/metadata/layer attributes as well as other supplementary information like PMI. Application Framework: offers solutions for handling application-specific data. DRAW Test Harness: implements a scripting interface to OCCT algorithms based on Tcl-interpreter for interactive usage, automating processes, prototyping applications and testing purposes. 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