Open CASCADE Technology

Build OCCT

Before building OCCT, make sure to have all required third-party libraries installed. The list of required libraries depends on what OCCT modules will be used, and your preferences. The typical minimum is FreeType (necessary for Visualization) and Tcl/Tk (for DRAW). See requirements on 3rdparty libraries for a full list.

The easiest way to install third-party libraries is to download archive with pre-built binaries, corresponding to your target configuration, from Development Portal. You can also build third-party libraries from their sources, see Build 3rd-parties for instructions.

On Linux and macOS we recommend to use libraries maintained by distributive developers, when possible.

Building with CMake tool

This chapter describes the CMake-based build process, which is now suggested as a standard way to produce the binaries of Open CASCADE Technology from sources. OCCT requires CMake version 2.8.12 or later.

CMake is a tool that generates the actual project files for the selected target build system (e.g. Unix makefiles) or IDE (e.g. Visual Studio 2010). Here we describe the build procedure on the example of Windows platform with Visual Studio 2010. However, CMake is cross-platform and can be used to build OCCT on Linux and macOS in essentially the same way.

CMake deals with three directories: source, build or binary and installation.

  • The source directory is where the sources of OCCT are located in your file system;
  • The build or binary directory is where all files created during CMake configuration and generation process will be located. The mentioned process will be described below.
  • The installation directory is where binaries will be installed after building the INSTALL project that is created by CMake generation process, along with header files and resources required for OCCT use in applications.

The good practice is not to use the source directory as a build one. Different configurations should be built in different build directories to avoid conflicts. It is however possible to choose one installation directory for several configurations of OCCT (differentiated by platform, bitness, compiler and build type), for example:

d:/occt/                   - the source directory
d:/tmp/occt-build-vc10-x64 - the build directory with the generated
                             solution and other intermediate files created during a CMake tool working
d:/occt-install            - the installation directory that is
                             able to contain several OCCT configurations

Configuration process

For unexperienced users we recommend to start with cmake-gui – a cross-platform GUI tool provided by CMake on Windows, Mac and Linux. A command-line alternative, ccmake can also be used.

If the command-line tool is used, run the tool from the build directory with a single argument indicating the source (relative or absolute path) directory, and press c to configure:

cd d:/tmp/occt-build-vc10-x64
ccmake d:/occt

If the GUI tool is used, run this tool without additional arguments and after that specify the source directory by clicking Browse Source and the build (binary) one by clicking Browse Build:

Each configuration of the project should be built in its own directory. When building multiple configurations it is suggested to indicate in the name of build directories the system, bitness and compiler (e.g., d:/occt/build/win32-vc10).

Once the source and build directories are selected, "Configure" button should be pressed in order to start manual configuration process. It begins with selection of a target configurator. It is "Visual Studio 10 2010 Win64" in our example.

To build OCCT for Universal Windows Platform (UWP) specify the path to toolchain file for cross-compiling d:/occt/adm/templates/uwp.toolchain.config.cmake. Alternatively, if you are using CMake from the command line add options -DCMAKE_SYSTEM_NAME=WindowsStore -DCMAKE_SYSTEM_VERSION=10.0. Universal Windows Platform (UWP) is supported only on "Visual Studio 14 2015". File CASROOT/samples/xaml/ describes the building procedure of XAML (UWP) sample.

Once "Finish" button is pressed, the first pass of the configuration process is executed. At the end of the process, CMake outputs the list of environment variables, which have to be properly specified for successful configuration.

The error message provides some information about these variables. This message will appear after each pass of the process until all required variables are specified correctly.

The change of the state of some variables can lead to the appearance of new variables. The new variables appeared after the pass of the configuration process are highlighted with red color by CMake GUI tool.

There is "grouped" option, which groups variables with a common prefix.

The following table gives the full list of environment variables used at the configuration stage:

Variable Type Purpose
CMAKE_BUILD_TYPE String Specifies the build type on single-configuration generators (such as make). Possible values are Debug, Release and RelWithDebInfo
USE_FREETYPE Boolean Indicates whether FreeType product should be used in OCCT for text rendering
USE_FREEIMAGE Boolean Indicates whether FreeImage product should be used in OCCT visualization module for support of popular graphics image formats (PNG, BMP, etc.)
USE_OPENVR Boolean Indicates whether OpenVR product should be used in OCCT visualization module for support of Virtual Reality
USE_OPENGL Boolean Indicates whether TKOpenGl graphic driver using OpenGL library (desktop) should be built within OCCT visualization module
USE_GLES2 Boolean Indicates whether TKOpenGles graphic driver using OpenGL ES library (embedded OpenGL) should be built within OCCT visualization module
USE_RAPIDJSON Boolean Indicates whether RapidJSON product should be used in OCCT Data Exchange module for support of glTF mesh file format
USE_DRACO Boolean Indicates whether Draco product should be used in OCCT Data Exchange module for support of Draco compression in glTF mesh file format
USE_TK Boolean Indicates whether Tcl/Tk product should be used in OCCT Draw Harness module for user interface (in addition to Tcl, which is mandatory for Draw Harness)
USE_TBB Boolean Indicates whether TBB (Threading Building Blocks) 3rd party is used or not. Note that OCCT remains parallel even without TBB product
USE_VTK Boolean Indicates whether VTK 3rd party is used or not. OCCT comes with a bridge between CAD data representation and VTK by means of its dedicated VIS component (VTK Integration Services). You may skip this 3rd party unless you are planning to use VTK visualization for OCCT geometry. See the official documentation VTK Integration Services (VIS) for the details on VIS
3RDPARTY_DIR Path Defines the root directory where all required 3rd party products will be searched. Once you define this path it is very convenient to click "Configure" button in order to let CMake automatically detect all necessary products
3RDPARTY_FREETYPE_* Path Path to FreeType binaries
3RDPARTY_TCL_* 3RDPARTY_TK_* Path Path to Tcl/Tk binaries
3RDPARTY_FREEIMAGE* Path Path to FreeImage binaries
3RDPARTY_TBB* Path Path to TBB binaries
3RDPARTY_VTK_* Path Path to VTK binaries
BUILD_MODULE_<MODULE> Boolean Indicates whether the corresponding OCCT module should be built or not. It should be noted that some toolkits of a module can be built even if this module is not checked (this happens if some other modules depend on these toolkits). The main modules and their descriptions can be found in User Guides
BUILD_LIBRARY_TYPE String Specifies the type of library to be created. "Shared" libraries are linked dynamically and loaded at runtime. "Static" libraries are archives of object files used when linking other targets. Note that Draw Harness plugin system is incompatible with "Static" builds, and therefore it is disabled for these builds.
BUILD_ADDITIONAL_TOOLKITS String Semicolon-separated individual toolkits to include into build process. If you want to build some particular libraries (toolkits) only, then you may uncheck all modules in the corresponding BUILD_MODUE_<MODULE> options and provide the list of necessary libraries here. Of course, all dependencies will be resolved automatically
BUILD_YACCLEX Boolean Enables Flex/Bison lexical analyzers. OCCT source files relating to STEP reader and ExprIntrp functionality are generated automatically with Flex/Bison. Checking this option leads to automatic search of Flex/Bison binaries and regeneration of the mentioned files
BUILD_SAMPLES_MFC Boolean Indicates whether MFC samples should be built together with OCCT. This option is only relevant to Windows platforms
BUILD_SAMPLES_QT Boolean Indicates whether QT samples should be built together with OCCT.
BUILD_Inspector Boolean Indicates whether Inspector should be built together with OCCT.
BUILD_DOC_Overview Boolean Indicates whether OCCT overview documentation project should be created together with OCCT. It is not built together with OCCT. Checking this option leads to automatic search of Doxygen binaries. Its building calls Doxygen command to generate the documentation in HTML format
BUILD_PATCH Path Points to the directory recognized as a "patch" for OCCT. If specified, the files from this directory take precedence over the corresponding native OCCT sources. This way you are able to introduce patches to Open CASCADE Technology not affecting the original source distribution
BUILD_WITH_DEBUG Boolean Enables extended messages of many OCCT algorithms, usually printed to cout. These include messages on internal errors and special cases encountered, timing, etc.
BUILD_ENABLE_FPE_SIGNAL_HANDLER Boolean Enable/Disable the floating point exceptions (FPE) during DRAW execution only. Corresponding environment variable (CSF_FPE) can be changed manually in custom.bat/sh scripts without regeneration by CMake.
CMAKE_CONFIGURATION_TYPES String Semicolon-separated CMake configurations
INSTALL_DIR Path Points to the installation directory. INSTALL_DIR is a synonym of CMAKE_INSTALL_PREFIX. The user can specify both INSTALL_DIR or CMAKE_INSTALL_PREFIX
INSTALL_DIR_BIN Path Relative path to the binaries installation directory (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_BIN})
INSTALL_DIR_SCRIPT Path Relative path to the scripts installation directory (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_SCRIPT})
INSTALL_DIR_LIB Path Relative path to the libraries installation directory (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_LIB})
INSTALL_DIR_INCLUDE Path Relative path to the includes installation directory (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_INCLUDE})
INSTALL_DIR_RESOURCE Path Relative path to the resources installation directory (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_RESOURCE})
INSTALL_DIR_LAYOUT String Defines the structure of OCCT files (binaries, resources, headers, etc.) for the install directory. Two variants are predefined: for Windows (standard OCCT layout) and for Unix operating systems (standard Linux layout). If needed, the layout can be customized with INSTALL_DIR_* variables
INSTALL_DIR_DATA Path Relative path to the data files installation directory (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_DATA})
INSTALL_DIR_SAMPLES Path Relative path to the samples installation directory. Note that only "samples/tcl" folder will be installed. (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_SAMPLES})
INSTALL_DIR_TESTS Path Relative path to the tests installation directory (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_TESTS})
INSTALL_DIR_DOC Path Relative path to the documentation installation directory (absolute path is ${INSTALL_DIR}/${INSTALL_DIR_DOC})
INSTALL_FREETYPE Boolean Indicates whether FreeType binaries should be installed into the installation directory
INSTALL_FREEIMAGE Boolean Indicates whether FreeImage binaries should be installed into the installation directory
INSTALL_TBB Boolean Indicates whether TBB binaries should be installed into the installation directory
INSTALL_VTK Boolean Indicates whether VTK binaries should be installed into the installation directory
INSTALL_TCL Boolean Indicates whether TCL binaries should be installed into the installation directory
INSTALL_TEST_CASES Boolean Indicates whether non-regression OCCT test scripts should be installed into the installation directory
INSTALL_DOC_Overview Boolean Indicates whether OCCT overview documentation should be installed into the installation directory
Only the forward slashes ("/") are acceptable in the CMake options defining paths.

3rd party search mechanism

If 3RDPARTY_DIR directory is defined, then required 3rd party binaries are sought in it, and default system folders are ignored. The procedure expects to find binary and header files of each 3rd party product in its own sub-directory: bin, lib and include. The results of the search (achieved on the next pass of the configuration process) are recorded in the corresponding variables:

  • 3RDPARTY_<PRODUCT>_DIR – path to the 3rdparty directory (with directory name) (e.g. D:/3rdparty/tcltk-86-32);
  • 3RDPARTY_<PRODUCT>_LIBRARY_DIR – path to the directory containing a library (e.g. D:/3rdparty/tcltk-86-32/lib);
  • 3RDPARTY_<PRODUCT>_INCLUDE_DIR – path to the directory containing a header file (e.g., D:/3rdparty/tcltk-86-32/include);
  • 3RDPARTY_<PRODUCT>_DLL_DIR – path to the directory containing a shared library (e.g., D:/3rdparty/tcltk-86-32/bin) This variable is only relevant to Windows platforms.
Each library and include directory should be children of the product directory if the last one is defined.

The search process is as follows:

  1. Common path: 3RDPARTY_DIR
  2. Path to a particular 3rd-party library: 3RDPARTY_<PRODUCT>_DIR
  3. Paths to headers and binaries:

If a variable of any level is not defined (empty or <variable name>-NOTFOUND) and the upper level variable is defined, the content of the non-defined variable will be sought at the next configuration step. If the search process at level 3 does not find the required files, it seeks in default places.

If a search result (include path, or library path, or dll path) does not meet your expectations, you can change 3RDPARTY_<PRODUCT>_*_DIR variable, clear (if they are not empty) 3RDPARTY_<PRODUCT>_DLL_DIR, 3RDPARTY_<PRODUCT>_INCLUDE_DIR and 3RDPARTY_<PRODUCT>_LIBRARY_DIR variables (or clear one of them) and run the configuration process again.

At this time the search will be performed in the newly identified directory and the result will be recorded to corresponding variables (replace old value if it is necessary). For example, 3RDPARTY_FREETYPE_DIR variable


can be changed to


During the configuration process the related variables (3RDPARTY_FREETYPE_DLL_DIR, 3RDPARTY_FREETYPE_INCLUDE_DIR and 3RDPARTY_FREETYPE_LIBRARY_DIR) will be filled with new found values.

The names of searched libraries and header files are hard-coded. If there is the need to change their names, change appropriate CMake variables (edit CMakeCache.txt file or edit in cmake-gui in advance mode) without reconfiguration: 3RDPARTY_<PRODUCT>_INCLUDE for include, 3RDPARTY_<PRODUCT>_LIB for library and 3RDPARTY_<PRODUCT>_DLL for shared library.

Projects generation

Once the configuration process is done, the "Generate" button is used to prepare project files for the target IDE. In our exercise the Visual Studio solution will be automatically created in the build directory.


Go to the build folder, start the Visual Studio solution OCCT.sln and build it by clicking Build -> Build Solution.

By default, the build solution process skips the building of the INSTALL and Overview projects. When the building process is finished build:

  • Overview project to generate OCCT overview documentation (if BUILD_DOC_Overview variable is checked)
  • the INSTALL project to run the installation process

For this, right-click on the Overview/INSTALL project and select Project Only -> Build Only -> Overview/INSTALL in the solution explorer.


Installation is a process of extracting redistributable resources (binaries, include files etc) from the build directory into the installation one. The installation directory will be free of project files, intermediate object files and any other information related to the build routines.

Normally you use the installation directory of OCCT to link against your specific application. The directory structure is as follows:

data            - data files for OCCT (brep, iges, stp)
doc             - OCCT overview documentation in HTML format
inc             - header files
samples         - samples
src             - all required source files for OCCT
tests           - OCCT test suite
win32\vc10\bind - binary files (installed 3rdparties and occt)
          \libd - libraries (installed 3rdparties and occt)
The above example is given for debug configuration. However, it is generally safe to use the same installation directory for the release build. In the latter case the contents of install directory will be enriched with subdirectories and files related to the release configuration. In particular, the binaries directory win64 will be expanded as follows:
If CMake installation flags are enabled for the 3rd party products (e.g. INSTALL_FREETYPE), then the corresponding binaries will be copied to the same bin(d) and lib(d) directories together with the native binaries of OCCT. Such organization of libraries can be especially helpful if your OCCT-based software does not use itself the 3rd parties of Open CASCADE Technology (thus, there is no sense to pack them into dedicated directories).

The installation folder contains the scripts to run DRAWEXE (draw.bat or, samples (if they were installed) and overview.html (short-cut for installed OCCT overview documentation).

Cross-compiling (Android)

This section describes the steps to build OCCT libraries for Android from a complete source package with GNU make (makefiles). The steps on Windows 7 and Ubuntu 15.10 are similar. There is the only one difference: makefiles are built with mingw32-make on Windows and native GNU make on Ubuntu.

Required tools (download and install if it is required):

Run GUI tool provided by CMake and:

  • Specify the root folder of OCCT ($CASROOT, which contains CMakelists.txt file) by clicking Browse Source.
  • Specify the location (build folder) for CMake generated project files by clicking Browse Build.

Click Configure button. It opens the window with a drop-down list of generators supported by CMake project. Select "MinGW MakeFiles" item from the list

  • Choose "Specify toolchain file for cross-compiling", and click "Next".
  • Specify a toolchain file at the next dialog to android.toolchain.cmake, and click "Finish".

If ANDROID_NDK environment variable is not defined in current OS, add cache entry ANDROID_NDK (entry type is PATH) – path to the NDK folder ("Add Entry" button):

If on Windows the message is appeared: "CMake Error: CMake was unable to find a build program corresponding to "MinGW Makefiles" CMAKE_MAKE_PROGRAM is not set. You probably need to select a different build tool.", specify CMAKE_MAKE_PROGRAM to mingw32-make executable.

How to configure OCCT, see Configure section taking into account the specific configuration variables for Android:

  • ANDROID_ABI = armeabi-v7a
  • ANDROID_NDK_LAYOUT is equal to CMAKE_BUILD_TYPE variable

Click Generate button and wait until the generation process is finished. Then makefiles will appear in the build folder (e.g. D:/tmp/occt-android ).

Open console and go to the build folder. Type "mingw32-make" (Windows) or "make" (Ubuntu) to start build process:




Parallel building can be started with using -jN argument of "mingw32-make/make", where N is the number of building threads:

mingw32-make -j4


make -j4

Type "mingw32-make/make" with argument "install" to place the libraries to the install folder:

mingw32-make install


make install

Building with Genproj tool

genproj is a legacy tool (originated from command "wgenproj" in WOK) for generation of Visual Studio, Code::Blocks, Qt Creator (qmake), and XCode project files for building Open CASCADE Technology. These project files are placed inside OCCT directory (in adm subfolder) and use relative paths, thus can be moved together with sources. The project files included in official distribution of OCCT are generated by this tool.

If you have official distribution with project files included, you can use them directly without a need to call genproj.

genproj is a less flexible alternative to use of CMake build system (see Building with CMake tool), but still has some small features useful for OCCT development.

Configuration process

The environment is defined in the file (on Linux and macOS) or custom.bat (on Windows) which can be edited directly:

  • ARCH – architecture (32 or 64), affects only PATH variable for execution
  • HAVE_* – flags to enable or disable use of optional third-party products
  • CSF_OPT_* – paths to search for includes and binaries of all used third-party products
  • SHORTCUT_HEADERS – defines method for population of folder inc by header files. Supported methods are:
    • Copy - headers will be copied from src;
    • ShortCut - short-cut header files will be created, redirecting to same-named header located in src;
    • HardLink - hard links to headers located in src will be created.
  • VCVER – specification of format of project files, defining also version of Visual Studio to be used, and default name of the sub-folder for binaries:
  • Add paths to includes of used third-party libraries in variable CSF_OPT_INC.
  • Add paths to their binary libraries in variable CSF_OPT_LIB64.
  • For optional third-party libraries, set corresponding environment variable HAVE_<LIBRARY_NAME> to either false, e.g. export HAVE_FREEIMAGE=false.
VCVER Visual Studio version Windows Platform Binaries folder name
vc10 2010 (10) Desktop (Windows API) vc10
vc11 2012 (11) Desktop (Windows API) vc11
vc12 2013 (12) Desktop (Windows API) vc12
vc14 2015 (14) Desktop (Windows API) vc14
vc14-uwp 2015 (14) UWP (Universal Windows Platform) vc14-uwp
vc141 2017 (15) Desktop (Windows API) vc14
vc141-uwp 2017 (15) UWP (Universal Windows Platform) vc14-uwp
vc142 2019 (16) Desktop (Windows API) vc14
vc142-uwp 2019 (16) UWP (Universal Windows Platform) vc14-uwp

Alternatively, you can launch genconf, a GUI tool allowing to configure build options interactively. That tool will analyze your environment and propose you to choose available options:

  • Type and version of project files to generate (from the list of installed ones, detected by presence of environment variables like VS100COMNTOOLS on Windows platform).
  • Method to populate folder inc (short-cuts by default).
  • Location of third-party libraries (usually downloaded from OCCT web site, see above).
  • Path to common directory where third-party libraries are located (optional).
  • Paths to headers and binaries of the third-party libraries (found automatically basing on previous options; click button "Reset" to update).
  • Generation of PDB files within Release build ("Release with Debug info", false by default).

Below are screenshots of genconf tool on various platforms (Windows and Linux):

Click "Save" to store the specified configuration in custom.bat (Windows) or (other systems) file.

Projects generation

Launch genproj to update content of inc folder and generate project files after changes in OCCT code affecting layout or composition of source files.

To use genproj and genconf tools you need to have Tcl installed and accessible by PATH. If Tcl is not found, the tool may prompt you to enter the path to directory where Tcl can be found.
$ genproj.bat

Note that if custom.bat is not present, genproj will start genconf to configure environment.


Visual Studio

Launch msvc.bat to start Visual Studio with all necessary environment variables defined, and build the whole solution or required toolkits.

The MSVC project files are located in folders adm\msvc\vc.... Binaries are produced in win32 or win64 folders.

To start DRAW, launch draw.bat.


Code::Blocks is a cross-platform IDE which can be used for building OCCT on Linux, macOS and Windows platforms. The generated Code::Blocks project could be found within subfolder adm/<OS>/cbp.

To start Code::Blocks, launch script To build all toolkits, click Build->Build workspace in the menu bar.

To start DRAWEXE, which has been built with Code::Blocks on Mac OS X, run the script

./ cbp [d]

Option d is used if OCCT has been built in Debug mode.


XCode is an IDE for development on macOS platform and targeting macOS and iOS platforms. genproj tool comes with a legacy XCode project files generator, but CMake is a preferred way for building OCCT on macOS platform.

To start XCode, launch script To build a certain toolkit, select it in Scheme drop-down list in XCode toolbar, press Product in the menu and click Build button.

To build the entire OCCT:

  • Create a new empty project (select File -> New -> Project -> Empty project in the menu; input the project name, e.g. OCCT; then click Next and Create).
  • Drag and drop the OCCT folder in the created OCCT project in the Project navigator.
  • Select File -> New -> Target -> Aggregate in the menu.
  • Enter the project name (e.g. OCCT) and click Finish. The Build Phases tab will open.
  • Click "+" button to add the necessary toolkits to the target project. It is possible to select all toolkits by pressing Command+A combination.

To start DRAWEXE, which has been built with XCode on Mac OS X, perform the following steps:

1.Open Terminal application 2.Enter <OCCT_ROOT_DIR>:


3.Run the script

./ xcd [d]

Option d is used if OCCT has been built in Debug mode.