Install the VSG module

This is a run-time visualization system for interactive 3D viewing of Chrono simulations.

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

Features

The VSG module is used to display Chrono simulations in an interactive 3D view. Here are the main features:

  • Supports most visualization shapes specified as assets on Chrono physics objects (bodies, links, etc)
  • The following default mouse and key controls are supported:
    • mouse left button for camera rotation
    • mouse right button for camera x z motion
    • mouse wheel rotation for camera forward/backward
    • press arrows to have x z camera motion, press page up & down for y vertical motion

Dependencies

  • This module you requires the Vulkan SDK and the VSG libraries.

Building and installing prerequisistes

There are two prerequisites for building the Chrono VSG module:

  • Vulkan is a cross-platform API for 3D graphics. The Vulkan SDK can be downloaded from https://vulkan.lunarg.com/. Follow the installation instructions specific to your platform.

  • VulkanScenegraph is a graphics library built on the Vulkan graphics API. At this time, the VSG library, its dependencies, and additional related utility libraries must be built from sources.

    The official mechanism for building and installing all VSG dependencies is to use vsgFramework provided by the VSG developers. Note however that this approach will use the latest VSG development code and as such may be incompatible with the current Chrono::VSG module.

    To address this issue, we provide a set of scripts (for both Windows and Linux) in the contrib/build-scripts/vsg directory of the Chrono source tree. These scripts allow us to target specific releases of the VSG dependencies (i.e., tags in their respective GitHub repositories) and ensure compatibility with the current Chrono::VSG code.

The two approaches for building and installing the VSG dependencies are described in the next two sections. For the reasons detailed above, We strongly recommend using the provided VSG build scripts.

1. VSG Framework

The official way of obtaining all VSG prerequisites for the Chrono::VSG module is to build the vsgFramework which collects several VSG-related projects and facilitates their build and installation in one single step.

The VSG libraries are themselves under active development, and so is vsgFramework. While functional, things do occasionally break down and some fixes may be needed to get the necessary dependency libraries. The instructions below reflect the current state of the vsgFramework code.

  1. Clone the vsgFramework GitHub repository. Assume the sources are in a local directory [vsgFramework_source].
  2. Create a buid directory and an install directory for vsgFramework. Assume these are [vsgFramework_build] and [vsgFramework_install], respectively.
  3. Use CMake to configure vsgFramework. Note that the only components that are necessary for Chrono::VSG are assimp, vsgImGui, and vsgXchange. Enable the corresponding BUILD_*** CMake options and unselect all other.
  4. Set the installation directory (CMAKE_INSTALL_PREFIX) to be the [vsgFramework_install] directory created above.
  5. Note that vsgFramework can create either static or dynamic VSG libraries. Either type will work on Linux or on MacOS. However, only dynamic libraries (DLLs) work on Windows. Set the CMake variable BUILD_SHARED_LIBS accordingly.
  6. Complete CMake configuration and generate the build scripts.
  7. Build and install the vsgFramework libraries (using whatever is appropriate for the generator you selected in CMake; make, ninja, VS, etc.)
  8. The VSG headers, libraries, and DLLs (if appropriate) installed in [vsgFramework_install] must be made available and accessible to CMake during configuration of Chrono below. If needed (e.g., on Windows), add to the system PATH environment variable the directory [vsgFramework_install]/bin.
The assimp component requires zlib. On some Linux systems, installing the default zlib package may not provide a library that is suitable for dynamic linking. You may need to rebuild zlib yourself, making sure you generate position-independent code. In particular, if using GCC, make sure to add the flag -fPIC.

2. VSG build scripts

With the VSG libraries themselves under active development, their latest versions may be incompatible with the current Chrono::VSG code. To ensure compatibility between the Chrono::VSG and its VSG dependencies, we provide (with the Chrono source code) a set of scripts which download specific code versions of the VSG dependencies, build all necessary libraries, and install them in a user-specified location.

These scripts (buildVSG.bat and buildVSG.sh, for Windows and Linux, respectively) are available in the contrib/build-scripts/vsg directory of the Chrono repository.

  1. Copy the appropriate script and place in an arbitrary temporary directory.
  2. Edit the script copy to:
    • Force a download of the VSG library codes.
    • Specify the install directory (set the variable VSG_INSTALL_DIR).
    • Decide whether to build shared or static libraries and whether to also build debug libraries.
  3. Run the script (.\buildVSG.bat or sh buildVSG.sh, as appropriate) from the location of the script copy. This will create a temporary directory where all source repositories will be cloned and a set of directories where the individual VSG dependencies are built.
  4. The install directory will contain (under subdirectories of VSG_INSTALL_DIR/lib/cmake) all VSG CMake project configuration scripts required to configure Chrono with the Chrono::VSG module enabled.

Building instructions

Once the necessary dependencies are installed, perform the following steps to configure and build the Chrono::VSG module:

  1. Repeat the instructions for the full Chrono installation
  2. During CMake configuration, set ENABLE_MODULE_VSG to 'on', then press 'Configure'
  3. When prompted, provide the paths to the various VSG project configuration scripts (vsg_DIR, vsgImGui_DIR, and vsgXchange_DIR). For example, assuming you used the provided build scripts, these should be <VSG_INSTALL_DIR>/lib/cmake/vsg, <VSG_INSTALL_DIR>/lib/cmake/vsgImGui, and <VSG_INSTALL_DIR>/lib/cmake/vsgXchange, respectively.
  4. Press 'Configure' again, then 'Generate', and proceed as usual in the installation instructions.
When using shared libraries for third-party dependencies, you must ensure that these are found at run time.
On Windows, you can either copy the dependency DLLs to the same directory as the executables or else add the path to these shared libraries to the PATH environment variable.
On Linux, you may need to append to the LD_LIBRARY_PATH environment variable.

Usage

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