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Visualisation of Grid / SciDAC format density fields using VTK (visualisation toolkit). Peter Boyle, 2025.
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Uses:
https://vtk.org
Files are, for example, those produced by
Grid/HMC/ComputeWilsonFlow.cc
and
Grid/HMC/site_plaquette.cc
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Prerequisites:
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1) Install ffmpeg-7.0.2 (developer install, includes headers and libraries).
MacOS note: must install ffmpeg from source -- homebrew only installs binaries.
https://ffmpeg.org/download.html#releases
Note: the latest ffmpeg (7.1.1) broke software compatibility with VTK.
2) Build and install VTK-9.4.2, with FFMEG support enabled.
This is particularly involved on MacOS, so documented here.
cd VTK-9.4.2
mkdir build
cd build
ccmake ..
Using ccmake editor, set:
FFMPEG_DIR /usr/local
Toggle "advanced mode" (t)
Set:
CMAKE_EXE_LINKER_FLAGS
CMAKE_MODULE_LINKER_FLAGS
CMAKE_SHARED_LINKER_FLAGS
each to:
-framework Foundation -framework AudioToolbox -framework CoreAudio -liconv -lm -framework AVFoundation -framework CoreVideo -framework CoreMedia -framework CoreGraphics -framework AudioToolbox -framework OpenGL -framework OpenGL -framework VideoToolbox -framework CoreImage -framework AppKit -framework CoreFoundation -framework CoreServices -lz -lbz2 -Wl,-framework,CoreFoundation -Wl,-framework,Security -L/usr/local/lib -lavdevice -lavfilter -lavformat -lavcodec -lswresample -lswscale -lavutil
Set paths for each of
FFMPEG_DIR /usr/local
FFMPEG_avcodec_INCLUDE_DIR /usr/local/include
FFMPEG_avcodec_LIBRARY /usr/local/lib/libavcodec.a
FFMPEG_avdevice_INCLUDE_DIR /usr/local/include
FFMPEG_avdevice_LIBRARY /usr/local/lib/libavdevice.a
FFMPEG_avfilter_INCLUDE_DIR /usr/local/include
FFMPEG_avfilter_LIBRARY /usr/local/lib/libavfilter.a
FFMPEG_avformat_INCLUDE_DIR /usr/local/include
FFMPEG_avformat_LIBRARY /usr/local/lib/libavformat.a
FFMPEG_avresample_INCLUDE_DIR /usr/local/include
FFMPEG_avresample_LIBRARY /usr/local/lib/libavresample.a
FFMPEG_avutil_INCLUDE_DIR /usr/local/include
FFMPEG_avutil_LIBRARY /usr/local/lib/libavutil.a
FFMPEG_swresample_INCLUDE_DIR /usr/local/include
FFMPEG_swresample_LIBRARY /usr/local/lib/libswresample.a
FFMPEG_swscale_INCLUDE_DIR /usr/local/include
FFMPEG_swscale_LIBRARY /usr/local/lib/libswscale.a
VTK_MODULE_ENABLE_VTK_IOFFMPEG YES
VTK really should make it easier to pick up the flags required for FFMPEG linkage, especially as they are very quirky on MacOS.
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Aurora compilation:
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module load ffmpeg
download & untar: VTK-7.0.2
mkdir build
cd build
ccmake ../
"t"
Enable: VTK_MODULE_ENABLE_VTK_IOFFMPEG YES
"configure" ; should "discover" the installed ffmpeg module
Still need an "X" connection to make the MPEG files.
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Grid:
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3) Build and install a version of Grid
4) Ensure "grid-config" is in your path.
5) cd Grid/visualisation/
libs=`grid-config --libs`
ldflags=`grid-config --ldflags`
cxxflags=`grid-config --cxxflags`
cxx=`grid-config --cxx`
mkdir build
cd build
LDFLAGS="$ldflags $libs " cmake .. -DCMAKE_CXX_COMPILER=$cxx -DCMAKE_CXX_FLAGS=$cxxflags
make
6) Invoke as:
FieldDensityAnimate --isosurface <float-from-0-to-5> --grid X.Y.Z.T --file1 SciDacDensityFile1 [--xlate] [--mpeg]
FieldDensityAnimate --isosurface <float-from-0-to-5> --grid X.Y.Z.T --file1 SciDacDensityFile1 --file2 SciDacDensityFile2 [--xlate] [--mpeg]
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Extensions
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7) Direct calling from Grid ?:
Not yet implemented, but could develop sufficient interface to write a Lattice scalar field into MPEG direct from running code.
8) Example python code: FieldDensity.py . This is not interfaced to Grid.
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Windowless generation of AVI files: must enable offscreen rendering. From Shuhei Yamamoto:
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Hi Peter,
To make visualization work on Frontier, I did the following.
For headless off-screen rendering, ccmake tabs in advanced mode shown below are set as indicated.
VTK_OPENGL_HAS_* off
VTK_USE_X off
VTK_DEFAULT_RENDER_WINDOW_OFFSCREEN on
VTK_DEFAULT_RENDER_WINDOW_HEADLESS on
The list can be greater than necessary.
VTK can fall back to EGL or OSMesa at runtime. So I installed mesa via spack (as well as nasm and yasm). Either mesa or meson package requires llvm-config, which is included after rocm6.1. On Frontier, I used /opt/rocm-6.2.4. The only problem is that llvm-config is located on /opt/rocm-6.2.4/llvm/bin, instead of /opt/rocm-6.2.4/bin. So I edited packages.yaml for spack so that the prefix for rocm compiler is /opt/rocm-6.2.4/llvm. Just in case, I also changed c and cxx to /opt/rocm-6.2.4/llvm/bin/amdclang, amdclang++, respectively, but this change might not be necessary.
After installation, I added a path to libOSMesa.so to LD_LIBRARY_PATH, for which there might be a better way such as specifying -rpath for OSMesa lib by editing cmake files.
In addition, I have editied CMakeLists.txt for vtk to force vtk to find OSMesa package via find_package(OSMesa REQUIRED) after list(INSERT CMAKE_MODULE_PATH 0 "${vtk_cmake_dir}"), as there is Find package in vtk/CMake. There will be more elegant method, but I was not able to find a tab to switch on OSMesa.
When I compiled vtk and linked to Grid visualization code, with ffmpeg option, it produces avi file.
Best,
Shuhei