What it does
An FFGL effect for Resolume Arena and Avenue: SW Schlieren. A 20 cm loudspeaker fires a short pulse into the air on every beat of Resolume's tempo, on every hit it hears in the music, or when you press Fire, and you watch your clip through that air the way a schlieren camera would. Each pulse spreads as a ring, light on one side and dark on the other, and the clip bends where it passes.
You can't see sound, but you can see what it does to light. A pressure wave squeezes the air, denser air bends light towards it by a few millionths of a radian, and a knife edge at the focus of a lens turns those bends into light and shade. August Toepler worked that out in 1864, and it's still how people photograph shock waves. So the plugin is the whole chain, in real units: a Pop, a Kick or a Blast at 120 to 190 dB a metre from the speaker, a spherical wave that fades as 1/r and steepens into shocks when it's loud or short enough (weak-shock theory's entropy solution, shocks and all), the beam's view of it summed through the air, and air's Gladstone–Dale constant bending the light.
The camera is the one cheat. Sound gets across the frame in milliseconds, so it's a high-speed camera, 30× to 30 000×, but the beats still arrive in real time and each one fires a pulse that you then watch slowed down. Four optics turn the bending into a picture: a knife edge you can turn, a colour wheel in its place, a shadowgraph screen where the bent light piles up into caustics, and background-oriented schlieren, with the clip as a backdrop up to 100 km behind the air (a few arcseconds of bend needs that kind of distance to move a pixel). Walls on the floor or round all four edges send every ring back to cross the others.
- A pulse on every beat, half beat, two beats or bar of Resolume's tempo, placed inside the frame where the beat fell, or on onsets in the music, or when you press Fire
- Three pulses, Pop, Kick and Blast, from 120 to 190 dB at a metre and 0.05 to 20 ms long, steepening into shocks by weak-shock theory when they're loud or short
- Four optics: a knife edge you can turn, colour schlieren, a shadowgraph screen with its caustics, and background-oriented schlieren with the clip as a distant backdrop
- Real units: a field 0.5 to 50 m wide, a camera from 30× to 30 000×, Sensitivity in arcseconds and Distance from 10 m to 100 km
- Rigid walls on the floor or all four edges, so the rings echo and cross
- Accent from the music's own dynamics, Grey Field for dark clips, and Pressure and Deflection views of the air on its own
- Universal macOS bundle and a Windows x64 DLL
Where it stands
v0.1.0, and early days. It's measured by an offline harness driving the plugin's own code on an Apple Silicon Mac, at two rasters and on Apple's software renderer: every pulse leaves within 6e-14 s of its beat, its front is where the speed of sound puts it to the pixel, the beam's view of each pulse matches a brute-force line-of-sight integral to 2e-6 of its peak, shocks form where weak-shock theory says and agree with an independent Godunov solver, each of the four optics obeys its law at every pixel sampled, and a rigid floor mirrors the field bit for bit. It catches sixteen models that are wrong on purpose and sixteen one-character sabotages of its own code, and all 21 controls the sweep can move change the picture. Past roughly 170 dB at a metre, the shocks are a good look rather than a prediction. It hasn't been loaded into Resolume on macOS yet, and no host has played it any music. On Windows it loads, registers and renders in Arena 7.27.1 on software rendering (no GPU, no sound) with every control as declared, and passed all 9 of the fleet's checks; eight or nine controls measurably changed the picture there across two runs, and the rest that act on the rings were too close to call against air that never sits still. There's a user guide, but no presets, browser demo or OpenFX port yet. Try it in your own rig before you trust it in a show.