fix: fall back to direct tile URLs on proxy errors

vendor/clouds3d.js

@@ -1834,13 +1834,24 @@ function tileProbeProxy() {
     probe(GROUND_TILE_PROXY + GROUND_TILE_Z + '/0/0.jpg',
         function () { GROUND_TILE_URL = GROUND_TILE_PROXY; });
 }
-function fetchTileBlob(tileX, tileY) {
-    // ESRI World_Street_Map format: {z}/{y}/{x}.jpg (y before x, jpg not png)
-    return fetch(GROUND_TILE_URL + GROUND_TILE_Z + '/' + tileY + '/' + tileX + '.jpg')
-        .then(function (r) {
+function fetchBlobWithFallback(primaryUrl, fallbackUrl) {
+    function get(url) {
+        return fetch(url).then(function (r) {
             if (!r.ok) throw new Error('tile http ' + r.status);
             return r.blob();
         });
+    }
+    return get(primaryUrl).catch(function (e) {
+        if (fallbackUrl && primaryUrl !== fallbackUrl) return get(fallbackUrl);
+        throw e;
+    });
+}
+function fetchTileBlob(tileX, tileY) {
+    // ESRI World_Street_Map format: {z}/{y}/{x}.jpg (y before x, jpg not png)
+    return fetchBlobWithFallback(
+        GROUND_TILE_URL + GROUND_TILE_Z + '/' + tileY + '/' + tileX + '.jpg',
+        GROUND_TILE_DIRECT + GROUND_TILE_Z + '/' + tileY + '/' + tileX + '.jpg'
+    );
 }
 
 function decodeToBitmap(blob) {
@@ -2181,11 +2192,10 @@ function loadElevTile(zx, zy, halfX, halfY) {
         });
     });
     function fetchFresh(db) {
-        return fetch(ELEV_TILE_URL + ELEV_Z + '/' + zx + '/' + zy + '.png')
-            .then(function (r) {
-                if (!r.ok) throw new Error('elev http ' + r.status);
-                return r.blob();
-            })
+        return fetchBlobWithFallback(
+            ELEV_TILE_URL + ELEV_Z + '/' + zx + '/' + zy + '.png',
+            ELEV_TILE_DIRECT + ELEV_Z + '/' + zx + '/' + zy + '.png'
+        )
             .then(function (blob) {
                 if (db) tileDbPut(db, { id: id, blob: blob, savedAt: Date.now() });
                 return decodeToBitmap(blob);