GNU Rocket is an intuitive new way of... bah, whatever. It's a sync-tracker, a tool for synchronizing music and visuals in demoscene productions. It consists of a GUI editor (using Qt), and an ANSI C library that can either communicate with the editor over a network socket, or play back an exported data-set.

The GNU Rocket editor uses qmake as a build-system abstraction, which can be used to output Makefiles, Visual Studio project files or can be built directly from QtCreator. See the qmake documentation for details.

GNU Rocket contains an example client called example_bass. This is a simple OpenGL, SDL 1.2 and BASS audio library application, that demonstrates how to use the GNU Rocket API.

Before compiling the example, you need to make sure you have recent SDL and BASS libraries and includes.

The header files and libraries can be installed local to the project by copying all .lib-files to the example_bass/lib/, all .h files to example_bass/include/, and all .dll files to the example_bass/.

Once the prerequisites are installed, the example can be compiled either by opening examples.sln and selecting "Build" -> "Build Solution" from Visual Studio 2008, or by doing "make example_bass/example_bass" on Unix-base systems.

The GNU Rocket editor is laid out like a music-tracker; tracks (or columns) and rows. Each track represents a separate "variable" in the demo, over the entire time-domain of the demo. Each row represents a specific point in time, and consists of a set of key frames. The key frames are interpolated over time according to their interpolation modes.

Each key frame has an interpolation mode associated with it, and that interpolation mode is valid until the next key frame is reached. The different interpolation modes are the following:

• Step : This is the simplest mode, and always returns the key's value.
• Linear : This does a linear interpolation between the current and the next key's values.
• Smooth : This interpolates in a smooth fashion, the exact function is what is usually called "smoothstep". Do not confuse this mode with splines; this only interpolates smoothly between two different values, it does not try to calculate tangents or any such things.
• Ramp : This is similar to "Linear", but additionally applies an exponentiation of the interpolation factor.

Some of the GNU Rocket editor's features are available through the menu and some keyboard shortcut. Here's a list of the supported keyboard shortcuts:

Please report bugs or other feedback to the GNU Rocket mailing list: gnu-rocket@googlegroups.com