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81 lines
3.0 KiB
JavaScript
81 lines
3.0 KiB
JavaScript
/**
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* @file Pure styling helpers for live traffic flow — level → bucket/color/
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* speed/density. Cesium-free so thresholds are unit-testable; the traffic
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* layer maps buckets to Cesium colors at spawn time.
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*
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* `level` is TomTom's `traffic_level`: current speed / free-flow speed,
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* 0..1 where 1 = free flow. Non-finite input degrades to free-flow/neutral
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* everywhere — a road with unusable data must render like the simulation,
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* never as a phantom traffic jam.
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*
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* @module data/trafficFlowStyle
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*/
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/** @const {number} Levels at/above this render as free-flowing (green). */
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const FREE_THRESHOLD = 0.85;
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/** @const {number} Levels at/above this (and below FREE) render slow (amber); below is jam (red). */
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const SLOW_THRESHOLD = 0.55;
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/**
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* Bucket color palette as Cesium-free rgba tuples ([r, g, b] 0–255 + alpha 0–1):
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* green #2ecc71 / amber #f0b23e / red #e05252, all at 0.9 alpha.
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* @type {{free:number[], slow:number[], jam:number[]}}
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*/
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export const FLOW_BUCKET_RGBA = {
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free: [46, 204, 113, 0.9],
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slow: [240, 178, 62, 0.9],
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jam: [224, 82, 82, 0.9],
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};
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/**
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* Classify a traffic level into a congestion bucket.
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* @param {number} level - traffic_level 0..1 (1 = free flow).
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* @returns {'free'|'slow'|'jam'} Bucket name; non-finite input → 'free'.
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*/
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export function flowBucket(level) {
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if (!Number.isFinite(level)) return 'free';
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if (level >= FREE_THRESHOLD) return 'free';
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if (level >= SLOW_THRESHOLD) return 'slow';
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return 'jam';
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}
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/**
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* rgba tuple for a traffic level (bucket palette lookup).
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* @param {number} level - traffic_level 0..1.
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* @returns {number[]} [r, g, b, a] with rgb 0–255, alpha 0–1.
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*/
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export function flowColor(level) {
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return FLOW_BUCKET_RGBA[flowBucket(level)];
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}
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/**
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* Dot speed multiplier for a traffic level. Jammed roads crawl but never
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* freeze (0.15 floor keeps the layer visibly alive); free flow is unchanged.
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* @param {number} level - traffic_level 0..1.
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* @returns {number} Multiplier within [0.15, 1]; non-finite input → 1.
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*/
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export function flowSpeedScale(level) {
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if (!Number.isFinite(level)) return 1;
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return Math.min(1, Math.max(0.15, level));
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}
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/**
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* Dot density multiplier for a traffic level — congestion means more cars on
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* the road, so slower roads pack more dots: 1/max(level, 0.4), capped at 2.5.
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*
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* With `jamBoost` (the jamViz density prototype) the same curve keeps
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* climbing through deep jams — 1/max(level, 0.25), capped at 4.0 — so
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* gridlock gets visibly denser while ordinary jams barely change. The two
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* curves are identical for level ≥ 0.4.
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*
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* @param {number} level - traffic_level 0..1.
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* @param {Object} [opts]
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* @param {boolean} [opts.jamBoost=false] - Deepen the curve below the 2.5 cap.
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* @returns {number} Multiplier within [1, 2.5] (or [1, 4] boosted); non-finite input → 1.
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*/
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export function flowDensityMult(level, { jamBoost = false } = {}) {
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if (!Number.isFinite(level)) return 1;
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if (jamBoost) return Math.min(4, 1 / Math.max(level, 0.25));
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return Math.min(2.5, 1 / Math.max(level, 0.4));
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}
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