mirror of
https://github.com/bilawalsidhu/gods-eye-view.git
synced 2026-11-04 18:34:02 +00:00
Sameh Khamis
f68aa988ec
A view can carry the marks the app's annotate_map action draws, and links carry them in the an parameter, bounded in count and size. A tilted view of an area now places the camera behind its center so the area stays in the middle of the frame.
93 lines
2.7 KiB
JavaScript
93 lines
2.7 KiB
JavaScript
/**
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* Suggested views: the God's Eye View view that shows a tool's answer, and
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* the link that opens it when the app's address is known.
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*/
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import { createView, viewUrl } from '../view/index.js';
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import { areaCenter, areaRadiusKm } from './area.js';
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const MIN_ALTITUDE_M = 500;
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const MAX_ALTITUDE_M = 15_000_000;
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// A top-down view sees roughly this many meters of ground per meter of altitude.
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const GROUND_PER_ALTITUDE = 0.55;
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const POINT_ALTITUDE_M = 50_000;
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/** A camera looking straight down that frames a resolved area. */
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export function cameraForArea(area) {
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const center = areaCenter(area);
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return {
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lat: center.lat,
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lon: center.lon,
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altitude_m: Math.min(
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MAX_ALTITUDE_M,
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Math.max(
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MIN_ALTITUDE_M,
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(areaRadiusKm(area) * 1000) / GROUND_PER_ALTITUDE,
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),
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),
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};
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}
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const EARTH_RADIUS_M = 6_371_008.8;
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/**
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* The camera position for looking at a point from `altitudeM` with a heading
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* and a tilt: straight above it when looking down, otherwise pulled back
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* along the heading so the point stays in the middle of the view.
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*/
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export function cameraLookingAt(
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target,
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{ altitudeM, headingDeg = 0, pitchDeg = -90 },
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) {
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const camera = {
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lat: target.lat,
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lon: target.lon,
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altitude_m: altitudeM,
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heading_deg: headingDeg,
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pitch_deg: pitchDeg,
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};
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if (pitchDeg <= -89.5) return camera;
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// Ground distance from the camera to the point it looks at, on flat ground.
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const back = altitudeM / Math.tan((-Math.min(pitchDeg, -5) * Math.PI) / 180);
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const heading = (headingDeg * Math.PI) / 180;
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const lat =
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target.lat -
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((back * Math.cos(heading)) / EARTH_RADIUS_M) * (180 / Math.PI);
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const lon =
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target.lon -
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((back * Math.sin(heading)) /
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(EARTH_RADIUS_M * Math.cos((target.lat * Math.PI) / 180))) *
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(180 / Math.PI);
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return {
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...camera,
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lat: Math.max(-90, Math.min(90, lat)),
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lon: ((((lon + 180) % 360) + 360) % 360) - 180,
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};
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}
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/** The app's address, or null when it is not configured. */
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function appUrl(services) {
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try {
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return services.app?.baseUrl ? new URL(services.app.baseUrl).href : null;
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} catch {
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return null;
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}
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}
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/**
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* A view of an area or point with layers on and optionally something
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* followed, plus `url` (null without the app's address). A point is framed
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* from `altitudeM` above it.
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*/
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export function suggestView(
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services,
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{ area, point, layers = [], follow = null, altitudeM = POINT_ALTITUDE_M },
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) {
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const camera = area
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? cameraForArea(area)
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: { lat: point.lat, lon: point.lon, altitude_m: altitudeM };
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const view = createView({ camera, layers, follow });
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const base = appUrl(services);
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return { ...view, url: base ? viewUrl(base, view) : null };
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}
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