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OpenCamLib (OCL) is an open source library aiming to provide computer aided manufacturing (CAM) algorithms. FreeCAD uses OCL in the experimental Path Surface.svg 3D Surface path operations and other experimental features.





Note: Beginning with FreeCAD version 0.19, OCL should be included with all Windows distribution packages.

To install OCL on Windows, follow these instructions.

  1. Obtain the Python version of OpenCamLib (OCL).
    • Build from source using the Python version used by your FreeCAD version. Peter Lama's fork of the same source has project files for a MSVC build.
    • Download the Python 2.7 x86/x64 binary by sgrogan on GitHub.
    • Download the Python 3.6 x64 binary by sgrogan on GitHub.
  2. Navigate to your OCL build or binary folder
  3. Copy the ocl.pyd library file
  4. Proceed with one of the following four(4) options:
    • Navigate to your FreeCAD\lib folder, and paste the ocl.pyd file there. (This is the preferred option.)
    • Navigate to your FreeCAD\bin folder, and paste the ocl.pyd file there.
    • Navigate to your FreeCAD\Mod folder. Create a new folder, OCL. Enter the OCL folder and paste the ocl.pyd file.
    • Navigate to your %USERPROFILE%\AppData\Roaming\FreeCAD folder. Create a new folder, Mod. Enter the Mod folder. Create a new OCL folder. Enter the OCL folder and paste the ocl.pyd file. (This is the least preferred option.)
  5. Restart FreeCAD
  6. Verify proper installation
    1. Click ViewPanelsPython console.
    2. Type "import ocl" into the Python console and press the enter key.
    3. If no error appears, you have correctly installed OCL
      • If you receive an error:
        • Check the placement and name of the ocl.pyd file as instructed above
        • Verify the correct architecture type of the OCL library you installed - x86 or x64
        • Verify the Python version used to build the OCL library is the same as that of your FreeCAD software - 2.7 or 3.6 currently


The repository is here and contains basic installation instructions.

Before beginning installation, or during the installation process, you will probably find you need to install some additional packages:


For example:

sudo apt install cmake
sudo apt install libboost-program-options-dev
# Optional, for documentation:
sudo apt-get install doxygen
sudo apt-get install texlive-full

Note: the "libboost-program-options-dev" may be substituted with "libboost-all-dev".

If you are struggling, carefully review any error messages you get during the cmake and make phases as you may need to install additional packages.


  1. Install OpenCamLib from the AUR package.
  2. Then run the following code snippet inside FreeCAD's Python console
import sys
import ocl

Python 3

Identify the version of cmake you have installed with cmake --version

For cmake >= 3.12, add these flags:

cmake -DBUILD_PY_LIB=ON -DUSE_PY_3=ON -DCMAKE_BUILD_TYPE=Release ../src -Wno-dev

For cmake < 3.12 (like in Ubuntu 18.04, which has 3.10), first you'll need to edit src/pythonlib/pythonlib.cmake, and apply this patch:

Index: opencamlib-2019.07/src/pythonlib/pythonlib.cmake
--- opencamlib-2019.07.orig/src/pythonlib/pythonlib.cmake
+++ opencamlib-2019.07/src/pythonlib/pythonlib.cmake
@@ -48,13 +48,13 @@ if(${CMAKE_VERSION} VERSION_LESS "3.12.0
     message("Python not found")
-    COMMAND ${PYTHON_EXECUTABLE} -c "from distutils.sysconfig import get_python_lib; print get_python_lib(0,0,\"/usr/local\")"
+    COMMAND ${PYTHON_EXECUTABLE} -c "import site; print(site.getsitepackages()[-1])"
   ) # on Ubuntu 11.10 this outputs: /usr/local/lib/python2.7/dist-packages
-    COMMAND ${PYTHON_EXECUTABLE} -c "from distutils.sysconfig import get_python_lib; print get_python_lib(plat_specific=1,standard_lib=0,prefix=\"/usr/local\")"
+    COMMAND ${PYTHON_EXECUTABLE} -c "import site; print(site.getsitepackages()[-1])"

Then, in order for Python 3 to be detected correctly you'll need to add 2 more flags to the cmake line:


See the FreeCAD forum at Re: How to activate openCamLib after compiling it, and a few posts following.


git clone
cd opencamlib
mkdir build
cd build
cmake -DBUILD_PY_LIB=ON -DUSE_PY_3=ON -DCMAKE_BUILD_TYPE=Release .. -Wno-dev
make -j4
make install

To test the build enter the following in the Python console:

import area
import ocl

The return value should be:

['AdaptivePathDropCutter', 'AdaptivePathDropCutter_base', 'AdaptiveWaterline', 'AdaptiveWaterline_base', 'Arc', 'ArcSpanType', 'BallConeCutter', 'BallCutter', 'BatchDropCutter', 'BatchDropCutter_base', 'BatchPushCutter', 'BatchPushCutter_base', 'Bbox', 'BullConeCutter', 'BullCutter', 'CCPoint', 'CCType', 'CLPoint', 'CompBallCutter', 'CompCylCutter', 'ConeConeCutter', 'ConeCutter', 'CutterLocationSurface', 'CylConeCutter', 'CylCutter', 'Ellipse', 'EllipsePosition', 'Fiber', 'Fiber_base', 'Interval', 'Line', 'LineCLFilter', 'LineCLFilter_base', 'LineSpanType', 'MillingCutter', 'Path', 'PathDropCutter', 'PathDropCutter_base', 'Path_base', 'Point', 'STLReader', 'STLSurf', 'STLSurf_base', 'SpanType', 'Triangle', 'Triangle_base', 'Waterline', 'Waterline_base', 'WeaveVertexType', 'ZigZag', 'ZigZag_base', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', 'eps', 'epsD', 'epsF', 'version']

In case of an error the return value will be:

['__doc__', '__file__', '__loader__', '__name__', '__package__', '__path__', '__spec__']

For cmake the Release option is very important, when using Debug area and ocl will collide and either library will not load (depending on what what was loaded first).

More help

In case you run into difficulties, you may find additional help at these forum posts:


Thank you to Dr. Anders Wallin for providing OCL to the public.