mirror of
https://github.com/bilawalsidhu/gods-eye-view.git
synced 2026-11-04 10:24:02 +00:00
Sameh Khamis
e8e49a49e0
The vessel source accepts an optional area and sends it as lat, lon and radius_km. The vessel layer asks for the area the camera shows (centered on the middle of the screen, sized by camera height), or every vessel from high enough up, and asks again when the view moves or zooms by a quarter of that radius. vessels_in_area names its area too. Servers that hold every vessel may ignore the area; callers still keep only what is inside it.
32 lines
1.3 KiB
JavaScript
32 lines
1.3 KiB
JavaScript
/** Smallest area asked for around the view, in kilometres. */
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export const VIEW_AREA_MIN_RADIUS_KM = 10;
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/** Largest area asked for; a wider view asks for every vessel instead. */
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export const VIEW_AREA_MAX_RADIUS_KM = 450;
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/**
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* The radius worth asking for from a camera this high, in kilometres: about
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* the height, so the area covers what a camera looking down shows. Null when
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* the view is wide enough that every vessel is wanted.
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*/
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export function viewAreaRadiusKm(heightM) {
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if (!Number.isFinite(heightM)) return null;
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const radiusKm = heightM / 1000;
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if (radiusKm > VIEW_AREA_MAX_RADIUS_KM) return null;
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return Math.max(VIEW_AREA_MIN_RADIUS_KM, radiusKm);
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}
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/**
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* Whether a view moved far enough from the last area asked for to ask
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* again: its radius changed by a quarter, or its center moved a quarter of
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* the radius. Switching between an area and every vessel always counts.
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*/
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export function viewAreaMovedEnough(previous, next) {
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if (!previous || !next) return previous !== next;
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if (Math.abs(next.radiusKm - previous.radiusKm) >= previous.radiusKm * 0.25)
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return true;
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const lat = ((previous.lat + next.lat) / 2) * (Math.PI / 180);
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const dLat = (next.lat - previous.lat) * 111.32;
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const dLon = (next.lon - previous.lon) * 111.32 * Math.cos(lat);
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return Math.hypot(dLat, dLon) >= previous.radiusKm * 0.25;
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}
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