Compiling the system

Before continuing, please make sure that you have read and followed the instructions on cloning Mitsuba 2 and its dependencies and choosing desired variants.

Compiling Mitsuba 2 from scratch requires recent versions of CMake (at least 3.9.0) and Python (at least 3.6). Further platform-specific dependencies and compilation instructions are provided below for each operating system. Some additional steps are required for GPU-based backends that are described at the end of this section.

Linux

The build process under Linux requires several external dependencies that are easily installed using the system-provided package manager (e.g., apt-get under Ubuntu).

Note that recent Linux distributions include two different compilers that can both be used for C++ software development. GCC is typically the default, and Clang can be installed optionally. During the development of this project, we encountered many issues with GCC (mis-compilations, compiler errors, segmentation faults), and strongly recommend that you use Clang instead.

To fetch all dependencies and Clang, enter the following commands on Ubuntu:

# Install recent versions build tools, including Clang and libc++ (Clang's C++ library)
sudo apt install clang-9 libc++-9-dev libc++abi-9-dev cmake ninja-build

# Install libraries for image I/O and the graphical user interface
sudo apt install libz-dev libpng-dev libjpeg-dev libxrandr-dev libxinerama-dev libxcursor-dev

# Install required Python packages
sudo apt install python3-dev python3-distutils python3-setuptools

Additional packages are required to run the included test suite or to generate HTML documentation (see Developer guide). If those are interesting to you, also enter the following commands:

# For running tests
sudo apt install python3-pytest python3-pytest-xdist python3-numpy

# For generating the documentation
sudo apt install python3-sphinx python3-guzzle-sphinx-theme python3-sphinxcontrib.bibtex

Next, ensure that two environment variables CC and CXX are exported. You can either run these two commands manually before using CMake or—even better—add them to your ~/.bashrc file. This ensures that CMake will always use the correct compiler.

export CC=clang-9
export CXX=clang++-9

If you installed another version of Clang, the version suffix of course has to be adjusted. Now, compilation should be as simple as running the following from inside the mitsuba2 root directory:

# Create a directory where build products are stored
mkdir build
cd build
cmake -GNinja ..
ninja

Tested version

The above procedure will likely work on many different flavors of Linux (with slight adjustments for the package manager and package names). We have mainly worked with software environment listed below, and our instructions should work without modifications in that case.

  • Ubuntu 19.10

  • clang 9.0.0-2 (tags/RELEASE_900/final)

  • cmake 3.13.4

  • ninja 1.9.0

  • python 3.7.5

Windows

On Windows, a recent version of Visual Studio 2019 is required. Some tools such as git, CMake, or Python (e.g. via Miniconda 3) might need to be installed manually. Mitsuba’s build system requires access to Python >= 3.6 even if you do not plan to use Mitsuba’s python interface.

From the root mitsuba2 directory, the build can be configured with:

# To be safe, explicitly ask for the 64 bit version of Visual Studio
cmake -G "Visual Studio 16 2019" -A x64

Afterwards, open the generated mitsuba.sln file and proceed building as usual from within Visual Studio. You will probably also want to set the build mode to Release there.

Additional packages are required to run the included test suite or to generate HTML documentation (see Developer guide). If those are interesting to you, also enter the following commands:

conda install pytest numpy sphinx

Tested version

  • Windows 10

  • Visual Studio 2019 (Community Edition) Version 16.4.5

  • cmake 3.16.4 (64bit)

  • git 2.25.1 (64bit)

  • Miniconda3 4.7.12.1 (64bit)

macOS

On macOS, you will need to install Xcode, CMake, and Ninja. Additionally, running the Xcode command line tools once might be necessary:

xcode-select --install

Note that the default Python version installed with macOS is not compatible with Mitsuba 2, and a more recent version (at least 3.6) needs to be installed (e.g. via Miniconda 3 or Homebrew).

Now, compilation should be as simple as running the following from inside the mitsuba2 root directory:

mkdir build
cd build
cmake -GNinja ..
ninja

Tested version

  • macOS Catalina 10.15.2

  • Xcode 11.3.1

  • cmake 3.16.4

  • Python 3.7.3

Running Mitsuba

Once Mitsuba is compiled, run the setpath.sh/bat script to configure environment variables (PATH/LD_LIBRARY_PATH/PYTHONPATH) that are required to run Mitsuba.

# On Linux / Mac OS
source setpath.sh

# On Windows
C:/.../mitsuba2> setpath

Mitsuba can then be used to render scenes by typing

mitsuba scene.xml

where scene.xml is a Mitsuba scene file. Alternatively,

mitsuba -m scalar_spectral_polarized scene.xml

renders with a specific variant that was previously enabled in mitsuba.conf. Call mitsuba --help to print additional information about the various possible command line options.

GPU variants

Variants of Mitsuba that run on the GPU (e.g. gpu_rgb, gpu_autodiff_spectral, etc.) additionally depend on the NVIDIA CUDA Toolkit and NVIDIA OptiX. CUDA needs to be installed manually while OptiX 7 ships natively with the latest GPU driver. Make sure to have an up-to-date GPU driver if the framework fails to compile the GPU variants of Mitsuba.

Tested versions of CUDA include 10.0, 10.1, and 10.2. Only OptiX 7 is supported at this moment.

Warning

Neither GPU- nor differentiable rendering currently work on macOS, which is sadly unlikely to change in the future. Apple has expelled NVIDIA graphics (and therefore APIs like CUDA that Mitsuba depends on) from the Mac ecosystem some years ago. Please voice your concerns to Apple if you are unhappy with this state of affairs.

In case your CUDA installation is not automatically found by CMake (for instance because the directory is not in PATH), you need to either set the environment variable CUDACXX or the CMake cache entry CMAKE_CUDA_COMPILER to the full path to the compiler. E.g.

# Environment variable
export CUDACXX=/usr/local/cuda/bin/nvcc

# or

# As part of the CMake process
cmake .. -DCMAKE_CUDA_COMPILER=/usr/local/cuda/bin/nvcc

By default, Mitsuba is able to resolve the OptiX API itself, and therefore does not rely on the optix.h header file. The MTS_USE_OPTIX_HEADERS CMake flag can be used to turn off this feature if a developer wants to experiment with parts of the OptiX API not yet exposed to the framework.

Embree

Mitsuba’s scalar and packet backends can optionally use Intel’s Embree library for ray tracing instead of the builtin kd-tree in Mitsuba 2. To do so, invoke CMake with the -DMTS_ENABLE_EMBREE=1 parameter or use a visual CMake tool like cmake-gui or ccmake to flip the value of this parameter. Embree tends to be faster but lacks some features such as support for double precision ray intersection.