OCCT3D

Open-source 3D foundation

Open CASCADE Technology

Open CASCADE Technology (OCCT) is the open-source C++ foundation maintained by the OCCT3D team for CAD, CAM, CAE, and specialized 3D applications.

View source on GitHub Read documentation
GEOMETRY / TOPOLOGYB-REP MODEL01Model and analyzegeometry02Present and exchangedata03Build the productlayer
  1. 01Model and analyze geometry
  2. 02Present and exchange data
  3. 03Build the product layer

A modular C++ platform

Modular C++ toolkits for 3D applications

OCCT separates foundational mathematics, geometry, topology, modeling algorithms, visualization, exchange, and application data into explicit modules.

Teams can inspect the implementation, integrate at toolkit level, and keep their own product architecture around the open foundation.

Core capabilities

Modeling, visualization, exchange, and application data

Modeling and geometry

Create, inspect, transform, and repair curves, surfaces, meshes, and boundary-representation models.

  • Curves and surfaces
  • B-rep topology
  • Boolean and feature operations
  • Meshing and shape healing

Interactive visualization

Build desktop and embedded 3D experiences with presentation, selection, clipping, and rendering services.

  • Interactive 3D views
  • Selection and highlighting
  • Hidden-line removal
  • Materials and rendering

Data exchange

Move precise geometry, assemblies, names, colors, and attributes through established engineering formats.

  • STEP and IGES
  • Mesh and scene formats
  • XDE assemblies and metadata
  • Shared exchange wrappers

Application data

Organize long-lived engineering documents with transactions, persistence, attributes, and product structures.

  • OCAF documents
  • Transactions and undo
  • Attributes and persistence
  • Application structure
Explore the OCCT user guides

Where OCCT fits

Applications that construct, analyze, or exchange 3D models

Use OCCT when the application must do more than display a file: it must construct, analyze, transform, exchange, or persist engineering models.

OCCT
Specialized CADCAM and inspectionEngineering simulationMedical imagingArchitecture and BIMDesign automationDigital twinsTechnical viewers

Why OCCT

Source code, license, documentation, and release history

Review the platform through its license, source code, documentation, release history, and public development record.

Open-source terms

OCCT is distributed under LGPL 2.1 with an additional exception. Review the license itself for the terms that apply to your product.

Read the license

Native C++ control

Integrate at the module or toolkit boundary and keep ownership of the application architecture and user experience.

Technical overview

Public development

Inspect changes, issues, tests, and release tags in the same repository used to evolve the platform.

Open the repository

Professional paths

Add focused support, training, maintenance, or commercial components without replacing the open foundation.

Explore support

Developed in public

Documentation, source code, and community development

Start with the architecture and API documentation, build a focused example against representative data, then report observable behavior with a reproducible case.

Developer community GitHub repository

Using OCCT in a product

Need a commercial component or engineering support?

Build directly with OCCT, add a DevTool, or send a bounded technical question with the relevant version and workflow.

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