Module position

Position computation utilities for RPE charts.

Replicates the coordinate system used by the player at a fixed scene size of 1350×900. Provides functions to compute:

• Line positions (from event layers + parent chains)
• Note positions relative to their line (local coordinates)
• Note positions relative to the scene (world coordinates)

Coordinate system

Use p / o / d / w / h to convert between chart space and scene pixels (mirroring the game's Game.p/o/d/w/h helpers).

Usage

import { getLineState, getNotePosition, preprocess } from './chart-utils';

preprocess(chart);

// Where is line 0 at beat 8?
const state = getLineState(chart, 0, 8);
console.log(state.sceneX, state.sceneY, state.rotationRad);

// Where is note 3 on line 0 at beat 8?
const pos = getNotePosition(chart, 0, 3, 8);
if (pos) console.log(pos.sceneX, pos.sceneY);

// Find the note closest to clicked pixel (700, 450)
const closest = findClosestNote(chart, { x: 700, y: 450 }, 8, 0, 50);
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