Phosphor

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I wondered what a DOOM engine looks like if you draw it with a beam instead of pixels. The walls are lines. The corners are bright. Old frames decay.

Oscilloscope Raycaster

A DOOM-style engine where each wall is a glowing vertical line. Navigate a 14×14 labyrinth. The phosphor screen never fully clears — old views linger and decay behind the new one.

Initialising 0 cells traced

Arm the signal, then walk the labyrinth with WASD or the arrow keys. A / D turn. Close walls chime.

Cells Traced 0 / —

Facing 0°

Wall Distance — m

Controls

W / Arrow Up: move forward.
S / Arrow Down: move backward.
A / Arrow Left: turn left.
D / Arrow Right: turn right.

Build Notes

The scene uses a standard DDA raycaster — the same algorithm behind DOOM and Wolfenstein 3D. Instead of filling each column with a textured stripe, each column is a single-pixel vertical line stroke. Distance maps to brightness.

The oscilloscope effect comes from two canvas tricks: the screen is never fully cleared — a semi-transparent black fill decays the previous frame each tick, like phosphor persistence — and shadowBlur adds the green glow around each line.

Edge Logic

Wall corners glow brightest. When adjacent ray columns land on different surfaces, the transition is drawn as a second, wider line in near-white — the beam dwelling on the edge of something.

The oscilloscope aesthetic reverses what software rendering usually hides. In a normal raycaster, filled columns make distance invisible — every wall looks opaque and solid. Here, the thinness of the line is the rendering. Far walls are barely there. Close walls are bright enough to glow. The room only exists as a trace.

Canvas: 320 × 200 px, rendered as crisp low-resolution canvas.
Map: 14 × 14 grid; 0 = open cell, 1 = wall cell.
Field of view: 60 degrees (Math.PI / 3), cast across one ray per canvas column.
Raycaster: DDA grid stepping, up to 64 steps per ray, with side-hit tracking for wall brightness.
Phosphor persistence: Each frame covers the previous frame with rgba(0,0,0,0.22) instead of fully clearing it.
Beam color: RGB 51, 255, 102, with canvas shadowBlur for the green glow.
Motion: Move speed 3.5 u/s; turn speed 2.2 rad/s; collision margin 0.28 map units.
Audio path: Browser-native oscillator.type = 'triangle'; 55 Hz drone, close-wall chimes, and no NES-style PeriodicWave.

Live JavaScript asset: /assets/phosphor/main.js?v=20260404a.
Native Triangle vs. NES-Style Triangle: Phosphor is the native-triangle contrast point in the audio comparison.
Dead Beat: related software-rendered room and Web Audio experiment.
Falling Hall: later software-rendered descent with explicit bell-synthesis parameters.
chewgum-dsp v0.1.0: extracts the NES-style triangle and bell path used elsewhere; Phosphor does not use that library.

Shane Curry, "Phosphor," https://shanecurry.com/lab/toys/phosphor/, published 2026-04-04, updated 2026-04-30.