Release God's Eye View as open source

src/data/scenePick.js

@@ -0,0 +1,48 @@
+/**
+ * Validation for positions that came back from a Cesium screen pick.
+ *
+ * `scene.pickPosition()` reads the depth buffer. Over empty sky — high-altitude
+ * views where the pick ray misses everything renderable — that read can produce
+ * a Cartesian that is not a place on the globe. Feeding one to
+ * `Cartographic.fromCartesian` either throws
+ * `DeveloperError: normalized result is not a number`, returns undefined, or —
+ * worst of all — quietly succeeds and hands back somewhere underground.
+ *
+ * A pick that does not name a real place on the globe is a MISSED pick, so
+ * callers treat a degenerate result exactly as they already treat a miss.
+ */
+
+/**
+ * FLOOR. WGS84's polar radius is 6,356,752 m and the deepest bathymetry is
+ * ~11 km below the geoid, so nothing this app renders can sit nearer the
+ * ellipsoid's center than ~6,346,000 m. Six million keeps ~346 km of margin
+ * below that while still rejecting every core-interior value — and those are
+ * the dangerous ones, because they are finite and non-zero and so convert
+ * WITHOUT complaint: `(500, 0, 0)` becomes a point 6,378 km underground that
+ * reverse-geocodes as 0°, 0°.
+ */
+const MIN_PICK_MAGNITUDE_M = 6_000_000;
+
+/**
+ * CEILING. The highest thing this app draws is a geostationary satellite,
+ * 42,164 km from the center. A million kilometres is ~24× that (and well past
+ * the Moon), so it cannot reject a real contact — but it does reject the absurd
+ * finite magnitudes that overflow Cesium's geodetic iteration into NaN, which
+ * throws exactly like a NaN input does.
+ */
+const MAX_PICK_MAGNITUDE_M = 1_000_000_000;
+
+/**
+ * Whether a picked Cartesian names a real position on or above the globe, and
+ * so can be converted to a Cartographic both safely and meaningfully.
+ *
+ * @param {{x: number, y: number, z: number}|null|undefined} position
+ * @returns {boolean}
+ */
+export function isPickedWorldPosition(position) {
+  if (!position) return false;
+  const { x, y, z } = position;
+  if (!Number.isFinite(x) || !Number.isFinite(y) || !Number.isFinite(z)) return false;
+  const magnitude = Math.hypot(x, y, z);
+  return magnitude >= MIN_PICK_MAGNITUDE_M && magnitude <= MAX_PICK_MAGNITUDE_M;
+}