fix(annotations): cull and budget surface height sampling

src/annotations/screenAnnotationRenderer.js

@@ -83,6 +83,9 @@ export function createScreenAnnotationRenderer(
   const heightCache = new Map();
   const HEIGHT_CACHE_SOFT = 600; // target size; over this we evict keys not used this frame
   const HEIGHT_CACHE_HARD = 8000; // absolute ceiling (one big ring + others) — never exceeded
+  let cullingVolume = null;
+  const heightBounds = new Cesium.BoundingSphere(new Cesium.Cartesian3(), 9500);
+  let heightBudget = 32;
   let projGen = 0; // bumped each projection frame; entries used this frame are "hot"
   function trimHeightCache() {
     if (heightCache.size <= HEIGHT_CACHE_SOFT) return;
@@ -123,6 +126,13 @@ export function createScreenAnnotationRenderer(
       heightCache.set(key, cached);
       return cached.h;
     }
+    const now = Date.now();
+    if (cached && now < cached.nextAttempt) {
+      cached.gen = projGen;
+      return cached.h;
+    }
+    if (heightBudget <= 0) return cached?.h || 0;
+    heightBudget--;
     try {
       if (
         scene.clampToHeightSupported &&
@@ -144,7 +154,12 @@ export function createScreenAnnotationRenderer(
       /* tiles not ready */
     }
     const fallback = cached ? cached.h : 0;
-    heightCache.set(key, { h: fallback, settled: false, gen: projGen });
+    heightCache.set(key, {
+      h: fallback,
+      settled: false,
+      gen: projGen,
+      nextAttempt: now + 1000,
+    });
     trimHeightCache();
     return fallback;
   }
@@ -362,6 +377,24 @@ export function createScreenAnnotationRenderer(
     // Anchor at the real surface height (cached + validated), so marks sit on
     // the ground/building instead of at sea level. The settle-once cache keeps
     // it stable (no per-frame jitter that earlier broke nearby projections).
+    // Cheap conservative endpoint tests precede GPU-backed surface sampling.
+    // Testing the accepted height range avoids culling an elevated roof solely
+    // because its sea-level anchor lies just beyond the horizon.
+    const visibleAt = (height) => {
+      const point = Cesium.Cartesian3.fromDegrees(lon, lat, height);
+      Cesium.Cartesian3.subtract(point, scene.camera.positionWC, scratchDir);
+      return (
+        Cesium.Cartesian3.dot(scratchDir, scene.camera.directionWC) > 0 &&
+        occluder.isPointVisible(point)
+      );
+    };
+    Cesium.Cartesian3.fromDegrees(lon, lat, 0, undefined, heightBounds.center);
+    if (
+      cullingVolume?.computeVisibility(heightBounds) ===
+      Cesium.Intersect.OUTSIDE
+    )
+      return null;
+    if (!visibleAt(0) && !visibleAt(9000)) return null;
     const world = Cesium.Cartesian3.fromDegrees(
       lon,
       lat,
@@ -467,6 +500,13 @@ export function createScreenAnnotationRenderer(
 
   function projectAll() {
     if (!records.size) return;
+    heightBudget = 32;
+    cullingVolume =
+      scene.camera.frustum?.computeCullingVolume?.(
+        scene.camera.positionWC,
+        scene.camera.directionWC,
+        scene.camera.upWC,
+      ) || null;
     projGen += 1; // new frame: entries touched below are "hot" and survive trimming
     const trackedRect = trackedEntityRect();
     occluder.cameraPosition = scene.camera.positionWC;

src/annotations/screenAnnotationRenderer.test.mjs

@@ -152,10 +152,17 @@ test('outline upgrade preserves the existing SVG group identity', (t) => {
   });
 
   const camera = {
-    positionWC: Cesium.Cartesian3.ZERO,
-    directionWC: Cesium.Cartesian3.ZERO,
+    positionWC: Cesium.Cartesian3.fromDegrees(-97.5, 31.2, 1000000),
+    directionWC: Cesium.Cartesian3.normalize(
+      Cesium.Cartesian3.negate(
+        Cesium.Cartesian3.fromDegrees(-97.5, 31.2),
+        new Cesium.Cartesian3(),
+      ),
+      new Cesium.Cartesian3(),
+    ),
     positionCartographic: { height: 1000 },
   };
+  t.mock.method(Cesium.SceneTransforms, 'worldToWindowCoordinates', () => ({ x: 100, y: 100 }));
   const sampledAnchors = [];
   const scene = {
     camera,
@@ -326,3 +333,94 @@ test('an add that throws after inserting its group unwinds instead of orphaning
   );
   renderer.destroy();
 });
+
+test('hidden and back-facing annotations do not sample; visible unresolved heights have bounded retries', (t) => {
+  const previous = globalThis.document;
+  const previousRaf = globalThis.requestAnimationFrame;
+  globalThis.document = fakeDocument();
+  globalThis.requestAnimationFrame = (fn) => {
+    fn();
+    return 1;
+  };
+  t.after(() => {
+    globalThis.document = previous;
+    globalThis.requestAnimationFrame = previousRaf;
+  });
+  t.mock.timers.enable({ apis: ['setTimeout', 'Date'], now: 1000 });
+  t.mock.method(Cesium.SceneTransforms, 'worldToWindowCoordinates', () => ({
+    x: 100,
+    y: 100,
+  }));
+  const camera = {
+    positionWC: Cesium.Cartesian3.fromDegrees(0, 0, 100000),
+    directionWC: new Cesium.Cartesian3(-1, 0, 0),
+    positionCartographic: { height: 100000 },
+    moveEnd: new Cesium.Event(),
+  };
+  let samples = 0;
+  const postRender = new Cesium.Event();
+  const scene = {
+    camera,
+    canvas: { width: 800, height: 600 },
+    postRender,
+    clampToHeightSupported: true,
+    clampToHeight() {
+      samples++;
+    },
+    requestRender() {},
+  };
+  const renderer = createScreenAnnotationRenderer({ scene, camera });
+  const mark = (id, lon) => ({
+    id,
+    type: 'label',
+    anchor: { lon, lat: 0 },
+    label: id,
+  });
+  renderer.add(mark('far-side', 180));
+  for (let i = 0; i < 100; i++) postRender.raiseEvent();
+  assert.equal(samples, 0);
+  renderer.add(mark('near-side', 0));
+  for (let i = 0; i < 100; i++) postRender.raiseEvent();
+  assert.equal(samples, 1);
+  for (let i = 0; i < 10; i++) {
+    t.mock.timers.tick(1000);
+    postRender.raiseEvent();
+  }
+  assert.equal(samples, 11);
+  camera.moveEnd.raiseEvent();
+  postRender.raiseEvent();
+  assert.equal(samples, 11, 'camera events cannot bypass the retry interval');
+  renderer.update(mark('near-side', 0), { empty: true });
+  t.mock.timers.tick(1000);
+  postRender.raiseEvent();
+  assert.equal(samples, 11, 'hidden records do not sample');
+  camera.directionWC = new Cesium.Cartesian3(1, 0, 0);
+  renderer.update(mark('near-side', 0));
+  postRender.raiseEvent();
+  assert.equal(samples, 11, 'behind-camera anchors do not sample');
+  camera.directionWC = new Cesium.Cartesian3(-1, 0, 0);
+  camera.frustum = {
+    computeCullingVolume: () => ({
+      computeVisibility: () => Cesium.Intersect.OUTSIDE,
+    }),
+  };
+  postRender.raiseEvent();
+  assert.equal(samples, 11, 'outside-frustum anchors do not sample');
+  camera.frustum = null;
+  const before = samples;
+  renderer.add({
+    id: 'large-area',
+    type: 'area',
+    label: 'Area',
+    ring: Array.from({ length: 100 }, (_, i) => [0.001 + i / 10000, 0]),
+    anchor: { lon: 0, lat: 0 },
+  });
+  assert.equal(
+    samples - before,
+    32,
+    'a projection pass caps synchronous surface work',
+  );
+  renderer.destroy();
+  assert.equal(camera.moveEnd.numberOfListeners, 0);
+  assert.equal(postRender.numberOfListeners, 0);
+});