@doot-games/notefield

The scrolling notefield on a canvas. Upscroll, receptors near the top, notes rising from below to meet them, driven entirely by song time. Depends on @doot-games/noteskin. Used by gameplay and, in a narrow variant, by the editor.

Scroll

Scroll speed is XMOD, matching StepMania. A note beats_away from now sits beats_away * speed note-heights past the receptor, so pixels per second = (bpm / 60) * speed * noteSize. A speed of 2.4 travels 2.4 note-heights per beat.

API

createNotefield(canvas, config?) returns a renderer.

• observe() start a ResizeObserver and size the canvas. resize() sizes once. disconnect() stops observing.
• render(time, chart, opts?) draw one frame. opts: speed, judge, held (per-lane key-down array), beats, showFeedback.
• blast(lane, color, songTime) push an expanding hit ring.
• geom(), laneX(i), pps(chart, speed), yAtTime(t, now, chart, speed), timeAtY(y, now, chart, speed) geometry helpers for hit-testing, used by the editor.

config: recFrac (receptor position, default 0.18 from the top), maxGap, maxLaneW, spread, minRecY. When a judge is passed it must be built from the same chart, so its tracking array lines up by index and the renderer culls judged notes and draws holds and center feedback.