Install the CASCADE module

This is an optional module that adds 3D CAD file support (STEP format) for Chrono using the OpenCASCADE library.

Read the introduction to modules for a technical background on the modularity of the Chrono project.

Features

The CASCADE module uses the functions of the OpenCASCADE open-source library in order to allow loading CAD models that were saved in the STEP file format.

Here are the main features:

  • Load object shapes saved in STEP file format
  • Compute the center of mass, the mass, the inertia of shapes
  • Convert shapes in triangulated meshes for visualization

Requirements

  • To run applications based on this module:
  • To build this module:

Currently, the Chrono API is compatible with the OpenCASCADE v.7.4.0. Previous versions of OpenCASCADE are not compatible.

Building instructions

  1. Repeat the instructions for the full installation, but when you see the CMake window, you must add the following steps:
  2. Set ENABLE_MODULE_CASCADE as 'on', then press 'Configure' (to refresh the variable list)
  3. If prompted, set OpenCASCADE_DIR to the path to the OpenCASCADE project configuration script (OpenCASCADEConfig.cmake) is located
    • example Windows: C:\OpenCASCADE-7.4.0-vc14-64\opencascade-7.4.0\cmake
    • example Linux: usr/local/lib/cmake/opencascade
  4. Press 'Configure' again, then 'Generate', and proceed as usual in the installation instructions.
On Windows, to make the OpenCASCADE DLLs visible to the Chrono::Cascade demos:
  • Execute the env.bat script in the OpenCascade directory before launching the demo (but only from the same DOS shell, via command line), or
  • Set the path and environment variables to make these DLLs visible from anywhere.
    • to the PATH variable, add the paths containing the required OpenCASCADE .dll files (assuming you installed OpenCASCADE 7.4.0 in D:, otherwise put your paths), separating them with ; and no spaces between them:
      • D:\OpenCASCADE-7.4.0-vc14-64\opencascade-7.4.0\win64\vc14\bin
      • D:\OpenCASCADE-7.4.0-vc14-64\freetype-2.5.5-vc14-64\bin
      • D:\OpenCASCADE-7.4.0-vc14-64\freeimage-3.17.0-vc14-64\bin
      • D:\OpenCASCADE-7.4.0-vc14-64\ffmpeg-3.3.4-64\bin
    • optionally you may add also these environment variables (again, modify the path if you used another installation directory for OpenCASCADE)
      • CSF_LANGUAGE=us
      • MMGT_CLEAR=1
      • CSF_EXCEPTION_PROMPT=1
      • CSF_STEPDefaults=D:\OpenCASCADE-7.4.0-vc14-64\opencascade-7.4.0\src\XSTEPResource
On Linux, you may need to add the path to the OpenCascade shared libraries to the LD_LIBRARY_PATH environment variable. For example:
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib

On MacOS you have to build your own OpenCascade folder. Homebrew has a cascade module, but it isn't compatible with chrono_cascade. So remove it, if you had installed it before. At configuration with CMake, be sure to apply the correct value for OpenCASCADE_DIR, so Cmake can find it. You also have to add the correct path in the DYLD_LIBRARY_PATH environment variable:
export DYLD_LIBRARY_PATH=/opt/OCCT/lib:$DYLD_LIBRARY_PATH
In this example OpenCascade has been installed into /opt/OCCT. If you want to install it into somewhere else, adjust your settings. DYLD_LIBRARY_PATH is set in ${HOME}/.zprofle.

How to use it

  • Look at the API section of this module for documentation about classes and functions.
  • Look at the C++ source of demos to learn how to use the functions of this module.

Troubleshooting

  • if the executables hang, freeze or crash as soon as they are loaded, you are possibly using an older version of OpenCASCADE. Uninstall it, and upgrade it to the version supported in Chrono (see above), rebuild Chrono, and set the correct paths in environment variables.
  • Some users reported errors like "missing symbol in dll" when starting the executables even with the correct version of OpenCASCADE. This is most likely due to the fact that you already have an older version of OpenCASCADE installed somewhere, even if you do not know it, where the path to those older DLLs is taking precedence in your PATH environment variable. Solution: move your paths to OpenCASCADE DLLs before all other paths in the system PATH variable. This might be caused when you installed
    • some packages for Matlab, that use OpenCASCADE under the hood
    • some packages for Anaconda, that use OpenCASCADE under the hood