Videopaper

Live wallpapers for macOS — including a scientifically accurate, ray-traced black hole rendered in real time on your GPU.

Website & DMG download: videopaper.ssh.codes

Videopaper is a SwiftUI app that turns an ambient animation or a local video file into a desktop wallpaper across one or more monitors. macOS does not expose a public API for setting a video as the system wallpaper asset, so Videopaper uses desktop-level, click-through AppKit windows: motion renders over the static wallpaper while staying behind normal app windows.

The relativistic scenes

Three scenes (Sources/Videopaper/Services/BlackHoleRenderer.swift) are real Schwarzschild geodesic ray tracers in Metal, not video loops. The black hole:

• every pixel integrates the exact null-geodesic (Binet) equation d²u/dφ² = 3u² − u through curved spacetime with RK4 — gravitational lensing, the shadow, and the photon ring emerge from the math
• accretion disk with the Novikov–Thorne temperature profile, exact Doppler + gravitational redshift g = √(1−3M/r) / ((1−ΩL_z)√f_cam), relativistic beaming (I ∝ g⁴), and Planck-spectrum colors
• disk-plane crossings found analytically per half-winding and refined with cubic Hermite interpolation, so higher-order photon-ring images come from the same integrator
• HDR (rgba16Float) render → bright pass → separable Gaussian bloom → ACES tonemap, driven by a CVDisplayLink capped at 60 fps
• fully halts (zero CPU/GPU) when the wallpaper is occluded or the screen locks

The pulsar is an oblique-rotator neutron star with R = 4.2 GM/c^2 (compactness 0.48): the same geodesic integrator with a solid surface, so gravitational self-lensing brings the far side into view — both magnetic polar caps at once. A tilted corotating dipole drives hollow beam cones (the lighthouse flash emerges from the volume integral along bent rays), aurora-like L-shell glow, and a magnetic-thermal surface map (hot caps, cool ember belt on the magnetic equator). The quasar adds volumetrics along the bent rays: relativistic jets with per-sample Doppler boosting (beta = 0.88 — the counter-jet nearly vanishes, like real one-sided quasar jets), a clumpy absorbing dust torus with a disk-heated rim, an X-ray corona, and a hotter near-Eddington disk.

Features

• Built-in animated scenes: Black Hole, Pulsar, Quasar, Aurora, Stars, Sunrise, Daylight, Sunset, Moonlight, Prism, and Ember.
• Local video wallpaper playback with looping, speed, fit mode, audio mute/volume, and dimming controls.
• Multi-monitor detection with per-display enable toggles and per-monitor assignments — each display can use its own scene or video.
• Menu bar controls for applying, stopping, and changing the wallpaper.
• Local persistence for saved source, playback, display, and launch preferences.

Build & run

./script/build_and_run.sh

The script builds the SwiftPM app (macOS 14+), stages dist/Videopaper.app, and launches it. Or grab the prebuilt DMG from videopaper.ssh.codes.

License

MIT