scrawl
AI-assisted project. This codebase was created with Claude
(Anthropic), directed and reviewed by a human author. It has never been loaded into
Resolume on macOS.
On Windows both plugins load, register and draw in Resolume Arena 7.27.1 on a machine with
software rendering and no GPU or sound device, with every control as declared.
The numbers here are measured by an offline harness that drives the real
plugin classes in a headless GL context: a held drawing is the same picture to the bit
until the next one is due, the boil read back out of the rendered pixels matches the
hand's stated law to 2-3%, a line's cross-section sums to Line Width to a few thousandths
of a pixel, and a kick is on the page in the first drawing made after it. On Resolume's
own drum loops (through a stand-in for its FFT, see Status) every band's
onsets fall on the loops' sixteenth notes far beyond chance. The checks are re-run
against fourteen models that are wrong on purpose and have to fail, eight one-character
mutants of the shipped shaders and C++ have to be caught, and a control sweep fails if any
parameter does nothing.
Hand-drawn doodles to the music, for Resolume Arena/Avenue, as two FFGL plugins: SW
Scrawl, a source, and SW Scrawl Over, the same over your clip. Rings of sound coming
off the speakers, impact stars on the snare, a zigzag bolt on the big kicks, little curls
floating up off the hi-hats, and one long wobbly line that is the music itself. They're
redrawn twelve times a second by a hand that can't hold still, so every line boils.
It's after the sound effects in Edgar Wright's Scott Pilgrim vs. the World (2010), where
a basement band's noise gets drawn into the air in felt tip. The plugin borrows the idea
and none of the film's artwork, and it has nothing to do with the film's makers.
SW Scrawl Over at its defaults on Resolume's own NeonRoom2 clip, with its Beat 001
loop driving it, 1.5 s in. Rendered by the plugin's offline harness (sctest --over --pipe --wav), not captured from Resolume.
Download
v0.1.0 — prebuilt for macOS and Windows. Pick your platform:
All builds, checksums and release notes: github.com/stoatworks-labs/scrawl/releases.
macOS builds are signed and notarised and open normally. The Windows builds are unsigned, so SmartScreen warns once.
The one idea
Every drawing is a new pass of a hand that can't hold still. Effects animation is
drawn again for every drawing, twelve a second on twos, and no two passes of a pen land in
the same place. So each doodle has an intended path, a ring or a spike or a zigzag, and
each drawing of it gets its own error from the hand:
- the boil, a wobble along the line's normal: three sinusoids in arc length whose
wavelengths belong to the doodle (a hand has a character) and whose phases belong to
the drawing;
- registration, the whole pass landing a little off and a little twisted, as when a
sheet isn't quite back on the pegs;
- pressure, the pen landing at the start of a stroke, lifting off the end, and pressing
unevenly in between.
The error scales with the gesture, A = Wobble × (0.003 + 0.02 × extent) frame heights, so
a big circle wanders further than a small tick. Between drawings everything holds still,
the picture included. That's the whole look, and the rest falls out of it:
- The line boils at 24, 12 or 8 drawings a second, and nothing moves in between, which
is what makes hand-drawn animation look hand-drawn.
- Circles don't close. A hand-drawn ring runs on past where it started, a little wide of
it.
- Strokes taper where the pen lands and lifts, and a stroke being written on stops
abruptly at the pen.
- Wobble 0 is a plotter: no boil, no registration error and no wander in the pen's
pressure, so a still doodle comes out the same in every drawing. The ends still taper,
since landing and lifting don't depend on Wobble.
- Passes draws everything two or three times with independent errors, for the sketchy
doubled line.
The GPU decides nothing. The hand makes every line on the CPU as a chain of capsules; the
shaders rasterise their union, blur a quarter-size copy for the glow, and lay it over the
clip.
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