libopendrop

libopendrop is a visualizer library à la Milkdrop2 or ProjectM. However, unlike both Milkdrop2 and ProjectM, it is implemented using modern C++17 with a central focus on correctness, performance, and simplicity.

Preset authoring is not restricted by an arbitrary shader model; while the underlying libopendrop engine is compatible with Milkdrop2 and ProjectM-style presets, libopendrop is more flexible in that it supports any GL draw calls within its preset implementations.

All presets for libopendrop are written natively in C++ and GLSL, and thus are significantly more performant than equivalent presets running in either Milkdrop2 or ProjectM.

Building

libopendrop builds using Bazel. A nice way to manage Bazel installs is to use bazelisk.

First, install Go:

Debian, Ubuntu, etc.

sudo apt-get install golang-go

Fedora

sudo dnf install golang-go

Next, put the golang bin directory onto your PATH. The following works for bash:

cat >>~/.bashrc << EOF
export PATH=\$PATH:\$HOME/go/bin
EOF
source ~/.bashrc

Now we can install bazelisk:

go get github.com/bazelbuild/bazelisk

Next, install the prerequisites for building libopendrop:

Debian, Ubuntu, etc.

sudo apt-get install libpulse-dev libgl-dev libglm-dev libncurses5-dev \
                     libncurses5 libsdl2-dev python3-pip

Fedora

sudo dnf install pulseaudio-libs-devel mesa-libGL-devel ncurses-devel \
                 ncurses SDL2-devel python3-pip

Use the runner program to build with bazelisk and run against the system audio source:

./run_libopendrop.sh -s system

The -s flag selects which pulseaudio source to use for input to the visualizer. Available options can be listed by passing -s ?:

./run_libopendrop.sh -s ?

Consult the usage for more information:

./run_libopendrop.sh -h

Toolchains and Cross-Compilation

libopendrop is configured to build for host platforms using either GNU gcc or LLVM clang. Cross-compilation for armeabihf targeting Raspberry Pi is also supported using LLVM clang. To select an alternative compiler, provide the -c argument to run_libopendrop.sh:

Argument	Compiler	Cross Compilation Target
-c gcc (default)	GNU gcc	None (host)
-c clang	LLVM clang	None (host)
-c pi	LLVM clang	Raspberry Pi (armeabihf)

Cross-compiled binaries cannot be run on the host when the architectures are incompatible. To build only and not run the binary afterwards, pass -z:

./run_libopendrop.sh -c pi -z

Cross-compilation support for Raspberry Pi is provided via a fork of rpi_bazel with a specially-configured sysroot image captured from a Raspberry Pi Raspbian system after installing various packages needed for other projects. This sysroot should work for building binaries that run on Raspbian (or Raspberry Pi OS). Some additional packages may need to be installed to match the configuration in the sysroot.

See the installation procedure in the setup_pi.sh script used to configure the Raspbian system described above for more details.

Testing

Unit tests are implemented for the libraries in libopendrop. Run all tests using:

./run_libopendrop.sh -t

The compiler for the tests can be changed with -c as above.

Sanitizers

AddressSanitizer and MemorySanitizer configurations are also available. Pass --config=msan or --config=asan:

./run_libopendrop.sh -t --config=asan

To get symbolized output from the sanitizers, Clang needs to know where to find llvm-symbolizer. On some distributions this binary has a numerical prefix, e.g. llvm-symbolizer-10. Adding a symlink somewhere on PATH with the canonical name fixes this:

sudo ln -s /usr/bin/llvm-symbolizer-10 /usr/bin/llvm-symbolizer

Preset Authoring

---

NOTE: The preset API is in flux and is likely to change significantly to achieve various features.

---

New presets can be forked from the existing set using preset/fork_template_preset.sh:

cd preset
./fork_template_preset.sh [-t some_existing_preset] new_preset

This will generate a new directory with the name new_preset forking some_existing_preset (or template_preset by default, if not specified with -t). To add this new preset to libopendrop, add it to the list in preset/BUILD:

PRESET_DEPS_LIST = [
  "//preset/alien_rorschach",
  "//preset/cube_boom",
  ...
  "//preset/new_preset",
]

Then, add a call to include the header in preset/preset_list.h:

// Preset includes
#include "preset/alien_rorschach/alien_rorschach.h"
#include "preset/cube_boom/cube_boom.h"
  ...
#include "preset/new_preset/new_preset.h"

And finally, add the class name to the list in the definition of opendrop::GetRandomPresetFromList():

  ...
return GetRandomPreset<opendrop::AlienRorschach,
                       opendrop::CubeBoom,
                         ...
                       opendrop::NewPreset>(std::forward<Args>(args)...);
  ...

Demo Video

The following is a demo of preset/cube_wreath with input audio from Vortex by Rezz and PEEKABOO. Be sure to enable 1080p60 for the best viewing experience.