treppe-gl

Render Shadertoy style GLSL shaders onto the treppe2000.

The shader is rendered into a 16x1 float framebuffer (x = stair step) and sent as RGBW16 UDP frames to the priority port (3124) of trepped on treppe.club.berlin.ccc.de. While it runs it overrides whatever else the stairs show. On exit it sends a black frame. The stairs power must be on (Bluescreen > Stairs).

nix-shell --run "python treppe_gl.py shaders/flow.glsl"
nix-shell --run "python treppe_gl.py shaders/pulse.glsl --dry-run"

Wrappers: ./treppe-run.sh <shader> [brightness] [more options] and ./treppe-dry.sh <shader> [brightness] [more options] (dry run, nothing is sent).

Options: --brightness 0-100 (scales output, default 100), --host, --port, --fps, --dry-run (send nothing), --no-window (headless), --white {extract,alpha,off}.

Shaders define mainImage(out vec4 fragColor, in vec2 fragCoord) and may use iResolution, iTime, iTimeDelta and iFrame. The file is reloaded when it changes; on a compile error the last working shader keeps running.

The same shader also runs at full size in the debug window, so derive the step from the resolution (floor(fragCoord.x / iResolution.x * 16.0)) or use fragCoord.x / iResolution.x, never raw fragCoord.x.

2D shaders: put // canvas: 256x48 compact: mean at the top of a shader (or use --canvas 256x48 --compact mean) and it is rendered as a real 2D picture of that size, then compacted to the 16 steps, each step being a 16 pixel wide (canvas width / 16) group of columns. The width must be a multiple of 16. compact: mean averages the group (default), max takes the brightest value per channel, row averages only the middle row. The debug window then shows the actual canvas on top. See shaders/reef-2d.glsl.

White channel: extract (default) sets w = min(r,g,b) and subtracts it from rgb, alpha uses the shader's alpha, off sends w = 0.

Debug window: top is the shader at full resolution, bottom are the 16 steps as sent (step numbers, colour, white bar). Steps 13-15 are greyed out, trepped only drives 13 channels. The step to channel mapping is done by trepped, frames are sent in step order.

Tests: nix-shell --run "python -m pytest tests".