Place every surface-bound layer through the shared placement

Import pins, infrastructure, ALPR, directions markers, bikeshare and the
Bhote Koshi story use createSurfacePoints instead of their own sampling,
budgets and partial triggers; ground snap, the mesh floor sampler,
traffic, transit, Street Level, the camera ground guard, wildlife and the
cockpit host read heights through readSurface or surfaceTriggers.
Per-layer offsets and floor policies stay as options. The import no
longer re-places pins on every camera move from the UI.

Calls to engine.surface outside src/globe go from 41 sampling calls to
10, each a raycast, a one-shot fly-to height or an asynchronous detailed
sample.

scripts/engine-coupling-baseline.json

@@ -2,7 +2,7 @@
   "metrics": {
     "attachRendererWithViewer": 33,
     "restoreFlagCopies": 9,
-    "surfaceCallsOutsideGlobe": 41,
+    "surfaceCallsOutsideGlobe": 10,
     "engineSwitchLayerIds": 3,
     "cesiumLayerRendererLines": 0,
     "navaraLayerRendererLines": 0,

src/cameraGroundGuard.js

@@ -14,6 +14,7 @@
  * lifts the eye if it sits below a usable clearance. Heading and pitch are
  * held, so the correction reads as the shot settling.
  */
+import { readSurface } from './globe/surfacePlacement.js';
 import * as geo from './geo/index.js';
 import { ownCameraArrival } from './data/cameraArrival.js';
 
@@ -30,17 +31,19 @@ const probeScratch = geo.cartographic.create();
 /**
  * Highest rendered surface across a few cells, with how many cells answered.
  * A cell whose tiles are not streamed yet contributes nothing.
- * @param {import('./globe/contract.js').GlobeSurface} surface Live surface.
+ * @param {import('./globe/contract.js').GlobeEngine} engine Live engine.
  * @param {Array<{lat: number, lon: number}>} cells Cells to probe.
  * @returns {{heightM: number, sampled: number}} Reading.
  */
-function sampleSurfaceM(surface, cells) {
+function sampleSurfaceM(engine, cells) {
   let heightM = Number.NaN;
   let sampled = 0;
   for (const cell of cells) {
     try {
-      const height = surface.sampleHeight(
+      const height = readSurface(
+        engine,
         geo.cartographic.fromDegrees(cell.lon, cell.lat, 0, probeScratch),
+        { prefer: 'scene' },
       );
       if (!Number.isFinite(height)) continue;
       sampled += 1;
@@ -135,7 +138,7 @@ export function guardCameraAboveGround(engine, at, options = {}) {
       lat: geo.math.toDegrees(carto.latitude),
       lon: geo.math.toDegrees(carto.longitude),
     };
-    const { heightM, sampled } = sampleSurfaceM(engine.surface, [
+    const { heightM, sampled } = sampleSurfaceM(engine, [
       { lat: at.lat, lon: at.lon },
       below,
     ]);

src/data/bhoteKoshiEvent.js

@@ -1,3 +1,4 @@
+import { readSurface } from '../globe/surfacePlacement.js';
 import { bindOverlayHost } from '../overlays/bindOverlayHost.js';
 import { worldOverlayFor } from '../overlays/worldOverlay.js';
 import { waitForSignal } from '../sources/requestDeadline.js';
@@ -1250,7 +1251,9 @@ export function createBhoteKoshiEventLayer({
       return anchor;
     const { lon, lat } = _evidenceTimeline[index]?.observation ?? {};
     const height = Number.isFinite(lon)
-      ? _engine.surface.terrainHeight(Cesium.Cartographic.fromDegrees(lon, lat))
+      ? readSurface(_engine, Cesium.Cartographic.fromDegrees(lon, lat), {
+          prefer: 'terrain',
+        })
       : undefined;
     if (Number.isFinite(height))
       Cesium.Cartesian3.fromDegrees(lon, lat, height + 18, undefined, anchor);
@@ -1626,7 +1629,7 @@ export function createBhoteKoshiEventLayer({
         // Sample once while preparing the shot, never from an animation frame.
         try {
           height =
-            _engine?.surface?.sampleHeight?.(position) ??
+            readSurface(_engine, position, { prefer: 'scene' }) ??
             _viewer?.scene?.sampleHeight?.(
               position,
               [_floodCore, _floodHalo, _surgePoint].filter(Boolean),
@@ -1634,7 +1637,7 @@ export function createBhoteKoshiEventLayer({
         } catch {}
         if (!Number.isFinite(height))
           height =
-            _engine?.surface?.terrainHeight(position) ??
+            readSurface(_engine, position, { prefer: 'terrain' }) ??
             _viewer?.scene?.globe?.getHeight?.(position);
       }
       if (!Number.isFinite(height)) height = point.fallbackElevationM;

src/data/geoImportDisplay.js

@@ -12,18 +12,14 @@
 // - ground overlays: image layers, or textured meshes at absolute altitudes,
 //   tinted and turned on a canvas when the KML says so; a plain colour is
 //   a ground fill or a mesh at an absolute altitude.
-// Nothing is pickable: an imported file has no card. Ground heights under
-// the points come from engine.surface, sampled again by refreshGround():
-// the terrain where the globe is drawn, else (3D tiles) the scene drawn
-// under a low camera, never an imported point (as Cesium's import kept its
-// pins out of height queries).
+// Nothing is pickable: an imported file has no card. Ground pins share
+// the surface placer and exclude every imported pin set from its samples.
 
+import { createSurfacePoints } from '../globe/surfacePlacement.js';
 import * as geo from '../geo/index.js';
 import { planImport } from './geoImportPlan.js';
 import {
-  BATCH,
   HORIZON_LIFT_M,
-  CLAMP_TILES_BELOW_M,
   MAX_ICON_PIXEL_RATIO,
   POLYGON_YIELD_MS,
 } from './geoImportLimits.js';
@@ -112,6 +108,7 @@ export async function drawImportedFile(
   let shown = visible;
   let destroyed = false;
   let removeCull = null;
+  let surface = null;
   const groundSets = [];
   const lines = [];
   const meshes = [];
@@ -129,6 +126,7 @@ export async function drawImportedFile(
 
   function release() {
     destroyed = true;
+    surface?.destroy();
     removeCull?.();
     removeCull = null;
     for (const set of groundSets.splice(0)) set.destroy();
@@ -276,14 +274,61 @@ export async function drawImportedFile(
       pointSetsOf(engine).add(look.set);
     }
     checkActive();
-    for (let from = 0; from < pins.length; from += BATCH) {
-      settle(heightContext(), from, from + BATCH);
-      if (from + BATCH < pins.length) {
-        await new Promise((resolve) => setTimeout(resolve, 0));
-        checkActive();
-      }
+    for (const pin of pins) {
+      pin.position = geo.cartesian3.fromDegrees(
+        pin.lon,
+        pin.lat,
+        pin.height ?? pin.offset,
+      );
+      pin.horizon = geo.cartesian3.fromDegrees(
+        pin.lon,
+        pin.lat,
+        (pin.height ?? pin.offset) + HORIZON_LIFT_M,
+      );
+      pin.surface = {
+        cartographic: geo.cartographic.fromDegrees(pin.lon, pin.lat),
+        position: pin.position,
+        offset: pin.offset,
+        get show() {
+          return shown && pin.height === null;
+        },
+      };
     }
     for (const look of looks.values()) writePins(look);
+    surface = createSurfacePoints(engine, {
+      groups: () =>
+        [...looks.values()]
+          .filter((look) => look.set)
+          .map((look) => ({
+            points: look.pins.map((pin) => pin.surface),
+            exclude: [...pointSetsOf(engine)],
+            set: {
+              set(index, { position }) {
+                const pin = look.pins[index];
+                pin.position = position;
+                pin.ground = pin.surface.surfaceHeight;
+                pin.horizon = geo.cartesian3.fromDegrees(
+                  pin.lon,
+                  pin.lat,
+                  pin.ground + pin.offset + HORIZON_LIFT_M,
+                );
+                look.set.set(index, { position });
+              },
+              commit() {
+                writePins(look);
+              },
+            },
+          })),
+      prefer: (point) =>
+        engine.maps.photorealActive() && point.surfaceHeight !== undefined
+          ? 'tiles'
+          : undefined,
+      heightOffset: (point) => point.offset,
+      estimateGround: true,
+      screenMargin: 0,
+      request,
+    });
+    surface.place();
     syncCull();
   } catch (error) {
     release();
@@ -291,79 +336,6 @@ export async function drawImportedFile(
   }
   request();
 
-  // Where heights come from now: the terrain, or the scene drawn under a
-  // low camera when the globe is not (3D tiles).
-  function heightContext() {
-    const surface = engine.surface;
-    const tiles =
-      (engine.imagery?.surface?.() ?? 'globe') !== 'globe' &&
-      surface.clampToHeightSupported &&
-      engine.camera.height() < CLAMP_TILES_BELOW_M;
-    return {
-      surface,
-      tiles,
-      exclude: [...pointSetsOf(engine)],
-      size: tiles ? engine.host.size() : null,
-    };
-  }
-
-  // Whether a position is in the window now: clamping to 3D tiles reads
-  // the tiles drawn, and a point elsewhere would only cost the query.
-  function inWindow(position, { width, height }) {
-    if (!engine.projector.horizonVisible(position)) return false;
-    const screen = engine.projector.worldToWindow(position);
-    return (
-      Boolean(screen) &&
-      screen.x >= 0 &&
-      screen.y >= 0 &&
-      screen.x <= width &&
-      screen.y <= height
-    );
-  }
-
-  // The ground under a pin, falling back to the last known one.
-  function groundUnder(pin, { surface, tiles, exclude, size }) {
-    const at = geo.cartographic.fromDegrees(pin.lon, pin.lat, 0);
-    const terrain = surface.terrainHeightSupported
-      ? surface.terrainHeight(at)
-      : undefined;
-    // A coarse ellipsoid mesh under 3D tiles can answer far below zero.
-    let ground = Number.isFinite(terrain)
-      ? tiles
-        ? Math.max(0, terrain)
-        : terrain
-      : (pin.ground ?? 0);
-    // On tiles the last height found stays until the tiles answer again:
-    // the terrain under them is not where the pin stands.
-    if (tiles) ground = pin.ground ?? ground;
-    if (
-      tiles &&
-      inWindow(geo.cartesian3.fromDegrees(pin.lon, pin.lat, ground), size)
-    ) {
-      const top = surface.clampToHeight(
-        geo.cartesian3.fromDegrees(pin.lon, pin.lat, Math.max(0, ground)),
-        exclude,
-      );
-      const height = top && geo.cartographic.fromCartesian(top)?.height;
-      ground = Number.isFinite(height) ? height : (pin.ground ?? ground);
-    }
-    return ground;
-  }
-
-  function settle(context, from = 0, to = pins.length) {
-    for (let i = from; i < Math.min(to, pins.length); i++) {
-      const pin = pins[i];
-      if (pin.height === null) pin.ground = groundUnder(pin, context);
-      const height = pin.height ?? pin.ground + pin.offset;
-      pin.position = geo.cartesian3.fromDegrees(pin.lon, pin.lat, height);
-      pin.horizon = geo.cartesian3.fromDegrees(
-        pin.lon,
-        pin.lat,
-        height + HORIZON_LIFT_M,
-      );
-    }
-  }
-
   function writePins(look) {
     const { set, pins } = look;
     if (!set) return;
@@ -443,6 +415,7 @@ export async function drawImportedFile(
         look.set?.commit();
       }
       syncCull();
+      if (shown) surface.place({ all: true });
       request();
     },
     /**
@@ -460,20 +433,9 @@ export async function drawImportedFile(
           ]);
       return out;
     },
-    /** Sample the ground under the points again (a map or the terrain changed). */
     async refreshGround(signal) {
-      const total = pins.length;
-      for (let from = 0; from < total; from += BATCH) {
-        signal?.throwIfAborted();
-        if (destroyed) return;
-        settle(heightContext(), from, from + BATCH);
-        if (from + BATCH < total)
-          await new Promise((resolve) => setTimeout(resolve, 0));
-      }
       signal?.throwIfAborted();
-      if (destroyed) return;
-      for (const look of looks.values()) writePins(look);
-      request();
+      surface.place({ all: true });
     },
     destroy() {
       if (destroyed) return;

src/data/geoImportDisplay.test.mjs

@@ -7,7 +7,6 @@ import {
   MAX_RAISED_RINGS,
   MAX_RAISED_VERTICES,
   OVERLAY_PIXEL_BUDGET,
-  BATCH,
 } from './geoImportLimits.js';
 import { drawImportedFile } from './geoImportDisplay.js';
 import { emptyRecords, geoJsonRecords } from './geoImportRecords.js';
@@ -34,6 +33,7 @@ for (const make of GROUND_HARNESSES) {
         },
       });
       const { engine, viewer } = harness;
+      engine.projector.worldToWindow = () => ({ x: 1, y: 1 });
       if (viewer) {
         viewer.imageryLayers = new Cesium.ImageryLayerCollection();
         viewer.scene.globe.show = true;
@@ -184,7 +184,8 @@ for (const make of GROUND_HARNESSES) {
       );
       assert.ok(pins.every(({ options }) => options.pickable === false));
       ground = 70;
-      await drawing.refreshGround();
+      await engine.maps.setTerrain({ kind: 'ellipsoid' });
+      engine.fake.frame();
       assert.deepEqual(heights(), [70, 80, 500]);
       ground = undefined;
       await drawing.refreshGround();
@@ -200,15 +201,14 @@ for (const make of GROUND_HARNESSES) {
       if (viewer) {
         viewer.scene.globe.show = false;
         viewer.scene.clampToHeightSupported = true;
-      } else engine.imagery.surface = () => 'tiles';
+      } else await engine.maps.setPhotorealTiles({});
       engine.camera.height = () => 1000;
       engine.projector.worldToWindow = () => ({ x: 1, y: 1 });
       engine.projector.horizonVisible = () => true;
       const excluded = [];
-      engine.surface.clampToHeight = (position, exclude) => {
+      engine.surface.sampleHeight = (_position, exclude) => {
         excluded.push(exclude);
-        const at = geo.cartographic.fromCartesian(position);
-        return geo.cartesian3.fromRadians(at.longitude, at.latitude, 2000);
+        return 2000;
       };
       const ground = await drawImportedFile(
         engine,
@@ -248,15 +248,12 @@ for (const make of GROUND_HARNESSES) {
   displayTest(
     'a pin on the tiles keeps its height while out of the window',
     async ({ engine }) => {
-      engine.imagery.surface = () => 'tiles';
+      await engine.maps.setPhotorealTiles({});
       engine.camera.height = () => 1000;
       engine.projector.horizonVisible = () => true;
       let visible = true;
       engine.projector.worldToWindow = () => (visible ? { x: 1, y: 1 } : null);
-      engine.surface.clampToHeight = (position) => {
-        const at = geo.cartographic.fromCartesian(position);
-        return geo.cartesian3.fromRadians(at.longitude, at.latitude, 500);
-      };
+      engine.surface.sampleHeight = () => 500;
       const drawing = await drawImportedFile(
         engine,
         geoJsonRecords({ type: 'Point', coordinates: [1, 2] }, '#39d0ff'),
@@ -272,12 +269,11 @@ for (const make of GROUND_HARNESSES) {
         projected = Math.round(geo.cartographic.fromCartesian(position).height);
         return projected >= 500 ? { x: 1, y: 1 } : null;
       };
-      engine.surface.clampToHeight = () =>
-        geo.cartesian3.fromDegrees(1, 2, 700);
+      engine.surface.sampleHeight = () => 700;
       await drawing.refreshGround();
       assert.equal(projected, 500, 'visibility uses the last measured height');
       assert.equal(height(), 700);
-      engine.surface.clampToHeight = () => undefined;
+      engine.surface.sampleHeight = () => undefined;
       await drawing.refreshGround();
       assert.equal(
         height(),
@@ -1258,17 +1254,17 @@ for (const make of GROUND_HARNESSES) {
   );
 
   displayTest(
-    'tile clamps only sample visible pins and yield between batches',
+    'tile samples only measure visible pins and yield between passes',
     async ({ engine }) => {
-      engine.imagery.surface = () => 'tiles';
+      await engine.maps.setPhotorealTiles({});
       engine.camera.height = () => 1000;
       engine.projector.horizonVisible = () => true;
       let visible = false;
       engine.projector.worldToWindow = () => (visible ? { x: 1, y: 1 } : null);
       let clamps = 0;
-      engine.surface.clampToHeight = (position) => {
+      engine.surface.sampleHeight = () => {
         clamps++;
-        return position;
+        return 0;
       };
       const records = geoJsonRecords(
         {
@@ -1285,8 +1281,11 @@ for (const make of GROUND_HARNESSES) {
         beforeYield = clamps;
       }, 0);
       await drawing.refreshGround();
+      await new Promise((resolve) => setTimeout(resolve, 0));
       clearTimeout(heartbeat);
-      assert.equal(beforeYield, BATCH);
+      assert.ok(beforeYield > 0 && beforeYield <= 16);
+      while (clamps < 600)
+        await new Promise((resolve) => setTimeout(resolve, 5));
       assert.equal(clamps, 600);
       drawing.destroy();
     },

src/data/geoImportLimits.js

@@ -41,12 +41,8 @@ export const MAX_RAISED_VERTICES = 32_768;
 export const MAX_RAISED_RINGS = 128;
 // Yield between polygons after half a 60 Hz frame, preserving the 8 ms work slice.
 export const POLYGON_YIELD_MS = 8;
-// Bound synchronous surface queries between yields; the existing batch is 256 pins.
-export const BATCH = 256;
 // Keep below-ellipsoid ground visible at the horizon, matching GhostMaps' 2 km lift.
 export const HORIZON_LIFT_M = 2000;
-// Limit tile clamping to a low camera, matching Cesium's 250 km threshold.
-export const CLAMP_TILES_BELOW_M = 250_000;
 
 // Cesium draws ground lines over fills and ground rectangles over layer rasters.
 export const POLYGON_ORDER = 0;

src/data/infrastructure.test.mjs

@@ -195,6 +195,8 @@ test('consumer build includes only infrastructure code and engine-free geometry,
       'scaleToGeodeticSurface',
       'simon1994',
     ].map((name) => `src/geo/${name}.js`),
+    'src/globe/surfaceDetail.js',
+    'src/globe/surfacePlacement.js',
     'src/layers/infrastructure/index.js',
     'src/layers/infrastructure/render/display.js',
     'src/layers/shared/color.js',

src/layers/alpr/render/display.js

@@ -16,6 +16,10 @@ import {
 // floor cell, else on the terrain, and waits unseen until one of them is
 // known; floors still resolving are asked for once per render.
 
+import {
+  createSurfacePoints,
+  readSurface,
+} from '../../../globe/surfacePlacement.js';
 import * as geo from '../../../geo/index.js';
 import { distanceScale } from '../../../globe/cpuPicks.js';
 import { rgbaFromCss } from '../../shared/color.js';
@@ -96,20 +100,23 @@ export function createAlprDisplay(engine, { state, services, source }) {
     geo.cartographic.fromDegrees(record.longitude, record.latitude);
   const ownSets = () => [normal, selected].filter(Boolean);
 
-  // Each sample is a depth render on Cesium, a raycast on Navara.
-  function sampleHeight(record) {
-    if (!engine.surface.supported) return undefined;
-    try {
-      return engine.surface.sampleHeight(location(record), ownSets());
-    } catch {
-      return undefined;
-    }
-  }
-  function terrainHeight(record) {
-    return engine.surface.terrainHeightSupported
-      ? engine.surface.terrainHeight(location(record))
-      : undefined;
-  }
+  const sampleHeight = (record) =>
+    readSurface(engine, location(record), {
+      exclude: ownSets(),
+      prefer: 'tiles',
+    });
+  const terrainHeight = (record) =>
+    readSurface(engine, location(record), { prefer: 'terrain' });
+  let surface = null;
+  const surfaceSet = {
+    set(index, { position }) {
+      const marker = [...markers.values()][index];
+      marker.position = position;
+      marker.resolved = validAlprGroundHeight(marker.surface.surfaceHeight);
+      syncMarker(marker);
+    },
+    commit: () => flushSprites(),
+  };
   /** The rendered surface under a camera, else the terrain, else its floor. */
   function surfaceHeight(record) {
     let height = sampleHeight(record);
@@ -131,6 +138,15 @@ export function createAlprDisplay(engine, { state, services, source }) {
     return {
       clamped,
       resolved,
+      surface: {
+        cartographic: location(record),
+        surfaceHeight: resolved ? height : undefined,
+        position: geo.cartesian3.fromDegrees(
+          record.longitude,
+          record.latitude,
+          resolved ? height + MARKER_FLOOR_LIFT_M : 0,
+        ),
+      },
       position: geo.cartesian3.fromDegrees(
         record.longitude,
         record.latitude,
@@ -250,6 +266,7 @@ export function createAlprDisplay(engine, { state, services, source }) {
       marker.drawn = null;
       syncMarker(marker);
     }
+    surface?.place({ all: true });
     resolveFloors();
     flushSprites();
     governorRequestRender('alpr-surface', engine);
@@ -461,6 +478,7 @@ export function createAlprDisplay(engine, { state, services, source }) {
     }
     flushSprites();
     if (changed) state.renderRevision += 1;
+    surface?.place();
     state.onScreen = countOnScreen();
     resolveFloors();
     const chosen = state.selectedId ? markers.get(state.selectedId) : null;
@@ -674,6 +692,20 @@ export function createAlprDisplay(engine, { state, services, source }) {
       normal.commit();
       selected.commit();
       initialized = true;
+      surface = createSurfacePoints(engine, {
+        groups: () => [
+          {
+            set: surfaceSet,
+            points: [...markers.values()].map((marker) => {
+              marker.surface.show = visible && marker.clamped;
+              return marker.surface;
+            }),
+            exclude: ownSets(),
+          },
+        ],
+        heightOffset: MARKER_FLOOR_LIFT_M,
+        request: () => governorRequestRender('alpr-surface', engine),
+      });
       removeMove = engine.camera.moveEnd.addEventListener(onMove);
       removeFrame = engine.frames.preRender.addEventListener(frame);
       overlay.init();
@@ -688,11 +720,14 @@ export function createAlprDisplay(engine, { state, services, source }) {
         : null;
       if (visible === next) return;
       visible = next;
+      if (visible) surface?.place({ all: true });
       for (const marker of markers.values()) syncMarker(marker);
       flushSprites();
     },
     destroy(options) {
       if (!initialized) return;
+      surface?.destroy();
+      surface = null;
       clearRendered(options);
       overlay.destroy();
       removeClick?.();

src/layers/alpr/render/display.test.mjs

@@ -281,6 +281,12 @@ for (const makeHarness of HARNESSES) {
       assert.ok(
         Math.abs(heightOf(h.badge('alpr-cameras', 0).position) - 321.5) < 0.01,
       );
+      h.terrain(410);
+      await h.engine.maps.setTerrain({ kind: 'ellipsoid' });
+      h.frame();
+      assert.ok(
+        Math.abs(heightOf(h.badge('alpr-cameras', 0).position) - 411.5) < 0.01,
+      );
       h.terrain(undefined);
       h.load(records(1).map((r) => ({ ...r, latitude: 30.0001 })));
       await settle();

src/layers/bhoteKoshi/render/display.test.mjs

@@ -54,7 +54,7 @@ test('an image that will not load rejects; story displays release their frame li
   const before = engine.frames.preRender.numberOfListeners;
   const story = display.draw(data);
   const locator = createBhoteKoshiLocatorDisplay(engine, { data });
-  assert.equal(engine.frames.preRender.numberOfListeners, before + 2);
+  assert.equal(engine.frames.preRender.numberOfListeners, before + 4);
   story.destroy();
   locator.destroy();
   assert.equal(engine.frames.preRender.numberOfListeners, before);

src/layers/bhoteKoshi/render/story.js

@@ -1,5 +1,6 @@
 // Samples the authored story graphics into ground sets and point movers.
 // The story owns reveal time; this display owns only its attached drawing.
+import { createSurfacePoints } from '../../../globe/surfacePlacement.js';
 import * as geo from '../../../geo/index.js';
 
 const value = (property) =>
@@ -25,6 +26,13 @@ export function drawStorySource(engine, data) {
   const entries = new Map();
   let order = 0;
   let destroyed = false;
+  const groups = new Set();
+  const surface = createSurfacePoints(engine, {
+    groups: () => groups,
+    prefer: 'scene',
+    estimateGround: true,
+    request: () => engine.render.request(data.name),
+  });
 
   function point(entity) {
     const graphics = entity.point;
@@ -49,22 +57,27 @@ export function drawStorySource(engine, data) {
           : null,
       },
     });
+    const row = { show: false };
+    const group = { set, points: [row] };
+    groups.add(group);
+    let authored;
     let previous;
     return {
       paint(show) {
         let position = value(entity.position);
         show = Boolean(show && value(graphics.show) !== false && position);
-        if (show && value(graphics.heightReference) === 1) {
-          const place = geo.cartographic.fromCartesian(position);
-          const height =
-            engine.surface.sampleHeight(place, [set]) ??
-            engine.surface.terrainHeight(place);
-          if (Number.isFinite(height))
-            position = geo.cartesian3.fromRadians(
-              place.longitude,
-              place.latitude,
-              height,
-            );
+        const clamped = show && value(graphics.heightReference) === 1;
+        if (clamped && !row.show) delete row.surfaceRevision;
+        row.show = clamped;
+        if (row.show) {
+          if (!authored || !geo.cartesian3.equals(position, authored)) {
+            authored = geo.cartesian3.clone(position);
+            row.cartographic = geo.cartographic.fromCartesian(position);
+            row.position = position;
+            delete row.surfaceRevision;
+            delete row.surfaceHeight;
+          }
+          position = row.position;
         }
         const fields = show
           ? {
@@ -92,7 +105,10 @@ export function drawStorySource(engine, data) {
         set.commit();
         previous = snapshot;
       },
-      destroy: () => set.destroy(),
+      destroy() {
+        groups.delete(group);
+        set.destroy();
+      },
     };
   }
 
@@ -185,6 +201,7 @@ export function drawStorySource(engine, data) {
       }
       item.paint(data.show !== false && value(entity.show) !== false);
     }
+    surface.place();
   }
   const off = engine.frames.preRender.addEventListener(frame);
   engine.render.request(data.name);
@@ -193,6 +210,7 @@ export function drawStorySource(engine, data) {
       if (destroyed) return;
       destroyed = true;
       off();
+      surface.destroy();
       for (const item of entries.values()) item.destroy();
       entries.clear();
       engine.render.request(data.name);

src/layers/bhoteKoshi/render/story.test.mjs

@@ -166,9 +166,11 @@ for (const make of GROUND_HARNESSES) {
       };
       return set;
     };
+    h.engine.projector.worldToWindow = () => ({ x: 1, y: 1 });
+    let ground = 1200;
     h.engine.surface.sampleHeight = (_place, exclude) => {
       assert.deepEqual(exclude, [pointSet]);
-      return 1200;
+      return ground;
     };
     const display = drawStorySource(h.engine, source);
     const frame = () => h.engine.fake.frame();
@@ -179,11 +181,21 @@ for (const make of GROUND_HARNESSES) {
     assert.equal(options.point.outlinePx, 3);
     assert.ok(
       Math.abs(
-        Cesium.Cartographic.fromCartesian(writes[0].position).height - 1200,
+        Cesium.Cartographic.fromCartesian(writes.at(-1).position).height - 1200,
       ) < 1e-6,
     );
     frame();
-    assert.equal(writes.length, 1);
+    const settled = writes.length;
+    frame();
+    assert.equal(writes.length, settled);
+    ground = 1250;
+    h.engine.fake.maps.terrainRevision++;
+    frame();
+    assert.ok(
+      Math.abs(
+        Cesium.Cartographic.fromCartesian(writes.at(-1).position).height - 1250,
+      ) < 0.01,
+    );
     size = 38;
     outline = 0.12;
     frame();

src/layers/bikeshare/render/display.js

@@ -12,6 +12,7 @@ import { writeSelectedMarker } from '../../shared/selectionKeeper.js';
 // - lifecycle: what init, enable, show, disable, detach and destroy own.
 // The layer (index.js) merges these into its parts.
 
+import { createSurfacePoints } from '../../../globe/surfacePlacement.js';
 import * as geo from '../../../geo/index.js';
 import { isPointerFree } from '../../../data/inputOwnership.js';
 import {
@@ -143,6 +144,37 @@ export function createBikeshareDisplay(engine, context) {
     commitStations();
   }
 
+  const surface = createSurfacePoints(engine, {
+    groups: () => [
+      {
+        points: [...state._stationRenderMap.values()].map(
+          (record) => record.point.surface,
+        ),
+        exclude: [stations, highlight].filter(Boolean),
+        set: stations && {
+          set(index, fields) {
+            const record = [...state._stationRenderMap.values()][index];
+            record.point.position = fields.position;
+            stations.set(index, fields);
+          },
+          commit() {
+            stations.commit();
+            commitHighlight();
+            selection.refreshSelectedCard();
+          },
+        },
+      },
+    ],
+    prefer: 'scene',
+    estimateGround: true,
+    heightOffset: POINT_HEIGHT_OFFSET_M,
+    request: () => engine.render.request(LAYER_ID),
+  });
+  function placeStations() {
+    commitStations();
+    surface.place();
+  }
+
   const rendering = createStationPoints(context, {
     // On the rendered surface where it answers, a small height otherwise.
     position(station) {
@@ -150,21 +182,20 @@ export function createBikeshareDisplay(engine, context) {
       const lat = Number(station?.lat);
       if (!Number.isFinite(lat) || !Number.isFinite(lon)) return null;
       ensureSets();
-      const sampled = engine.surface.supported
-        ? engine.surface.sampleHeight(
-            geo.cartographic.fromDegrees(lon, lat),
-            [stations, highlight].filter(Boolean),
-          )
-        : undefined;
-      const height =
-        (Number.isFinite(sampled) ? sampled : 0) + POINT_HEIGHT_OFFSET_M;
-      return geo.cartesian3.fromDegrees(lon, lat, height);
+      return geo.cartesian3.fromDegrees(lon, lat, POINT_HEIGHT_OFFSET_M);
     },
     create(record, { position, pixelSize }) {
       ensureSets();
       record.index = state._stationRenderMap.size;
       record.point = {
         position,
+        surface: {
+          position,
+          cartographic: geo.cartographic.fromCartesian(position),
+          get show() {
+            return visible;
+          },
+        },
         pixelSize,
         color: COLOR_NEUTRAL,
         show: true,
@@ -172,13 +203,13 @@ export function createBikeshareDisplay(engine, context) {
       writePoint(record);
       return record.point;
     },
-    afterAdd: commitStations,
+    afterAdd: placeStations,
     afterRemove() {
       reindex();
       commitStations();
     },
     update: writePoint,
-    afterUpdate: commitStations,
+    afterUpdate: placeStations,
   });
 
   const selection = {
@@ -335,6 +366,7 @@ export function createBikeshareDisplay(engine, context) {
     /** Shows the points and card, takes clicks and follows the camera. */
     show() {
       setVisible(true);
+      surface.place({ all: true });
       state._overlayHost.setVisible(BIKESHARE_SELECTED_OVERLAY_SOURCE_ID, true);
       parts.display._installClickHandler();
       // Pick ownership: station point ids are render-map keys.
@@ -374,6 +406,7 @@ export function createBikeshareDisplay(engine, context) {
       parts.display._clearSelection();
       releaseInput();
       detachCamera();
+      surface.destroy();
       destroySets();
       destroyed = true;
     },
@@ -393,6 +426,7 @@ export function createBikeshareDisplay(engine, context) {
       }
       detachCamera();
       parts.ingestion.abortAllInFlight();
+      surface.destroy();
       destroySets();
       destroyed = true;
       state._engine = null;

src/layers/bikeshare/render/display.test.mjs

@@ -272,6 +272,29 @@ for (const makeHarness of HARNESSES) {
       const point = f.layer.getDetectableObjects()[0].position;
       near(geo.cartographic.fromCartesian(point).height, 177, 'height');
 
+      f.display._selectStation(key);
+      f.surface(210);
+      await f.engine.maps.setTerrain({ kind: 'ellipsoid' });
+      f.engine.fake.frame();
+      near(
+        geo.cartographic.fromCartesian(
+          f.context.state._stationRenderMap.get(key).point.position,
+        ).height,
+        212,
+        'selected height',
+      );
+      const selected =
+        f.engine.fake.moverSet('bikeshare-selected').store.positions;
+      near(
+        geo.cartographic.fromCartesian({
+          x: selected[0],
+          y: selected[1],
+          z: selected[2],
+        }).height,
+        212,
+        'highlight height',
+      );
+
       const call = f.engine.fake.callsOf('surface.sampleHeight')[0];
       assert.deepEqual(
         call.args[1].map((set) => set.id),

src/layers/directions/render/display.js

@@ -13,6 +13,7 @@
 // Placement, routing, anchoring, selection and the route flight stay in the
 // layer.
 
+import { createSurfacePoints } from '../../../globe/surfacePlacement.js';
 import * as geo from '../../../geo/index.js';
 import {
   MARKER_COLORS,
@@ -121,31 +122,37 @@ export function createDirectionsDisplay(engine) {
 
   const own = () => [markers, letters, steps].filter(Boolean);
 
-  // The rendered surface under a marker (tiles, else terrain), without the
-  // display's own markers.
-  function groundPosition({ lon, lat }) {
-    const carto = geo.cartographic.fromDegrees(lon, lat);
-    let height;
-    try {
-      height = engine.surface.sampleHeightDetailed(carto, {
+  const markerPoints = LETTERS.map(() => ({ show: false }));
+  const surface = createSurfacePoints(engine, {
+    groups: () => [
+      {
+        points: markerPoints,
         exclude: own(),
-      })?.height;
-    } catch {
-      height = undefined;
-    }
-    return geo.cartesian3.fromDegrees(
-      lon,
-      lat,
-      Number.isFinite(height) ? height : 0,
-    );
-  }
+        set: {
+          set(index, fields) {
+            markers.set(index, fields);
+            letters?.set(index, fields);
+          },
+          commit() {
+            markers.commit();
+            letters?.commit();
+          },
+        },
+      },
+    ],
+    prefer: 'scene',
+    estimateGround: true,
+    request: () => engine.render.request(ID),
+  });
 
   function placeMarkers() {
     if (destroyed) return;
     LETTERS.forEach((letter, index) => {
       const point = ends[letter];
       const show = visible && Boolean(point);
-      const position = point ? groundPosition(point) : undefined;
+      const row = markerPoints[index];
+      row.show = show;
+      const position = point ? row.position : undefined;
       markers.set(index, {
         ...(position ? { position } : {}),
         color: MARKER_COLORS[letter],
@@ -157,6 +164,7 @@ export function createDirectionsDisplay(engine) {
         show,
       });
     });
+    surface.place();
     markers.setCount(LETTERS.length);
     markers.commit();
     if (letters) {
@@ -203,15 +211,6 @@ export function createDirectionsDisplay(engine) {
     steps.commit();
   }
 
-  const removeMoveEnd = engine.camera.moveEnd.addEventListener(() => {
-    if (ends.a || ends.b) placeMarkers();
-  });
-  let tilesLoaded = engine.surface.tilesLoaded();
-  const removeSurface = engine.frames.preRender.addEventListener(() => {
-    const loaded = engine.surface.tilesLoaded();
-    if (loaded && !tilesLoaded && visible && (ends.a || ends.b)) placeMarkers();
-    tilesLoaded = loaded;
-  });
   placeMarkers();
 
   return {
@@ -219,6 +218,12 @@ export function createDirectionsDisplay(engine) {
     setMarker(letter, point) {
       if (destroyed || !LETTERS.includes(letter)) return;
       ends[letter] = point ? { lon: point.lon, lat: point.lat } : null;
+      markerPoints[LETTERS.indexOf(letter)] = point
+        ? {
+            cartographic: geo.cartographic.fromDegrees(point.lon, point.lat),
+            position: geo.cartesian3.fromDegrees(point.lon, point.lat),
+          }
+        : { show: false };
       placeMarkers();
     },
     /** Draws the route ([lon, lat] pairs), or removes it (null). */
@@ -276,13 +281,13 @@ export function createDirectionsDisplay(engine) {
       visible = Boolean(next);
       route?.show(visible);
       placeMarkers();
+      if (visible) surface.place({ all: true });
       writeSteps();
     },
     destroy() {
       if (destroyed) return;
       destroyed = true;
-      removeMoveEnd();
-      removeSurface();
+      surface.destroy();
       route?.destroy();
       steps?.destroy();
       markers.destroy();

src/layers/directions/render/display.test.mjs

@@ -351,3 +351,30 @@ test('route endpoints refine when the surface finishes loading', (t) => {
     ) < 0.01,
   );
 });
+
+test('A/B heights follow a terrain replacement with a parked camera', async (t) => {
+  const engine = createFakeEngine();
+  t.after(() => engine.destroy());
+  engine.projector.worldToWindow = () => ({ x: 1, y: 1 });
+  engine.fake.script('terrainHeight', 40);
+  const display = createDirectionsDisplay(engine);
+  t.after(() => display.destroy());
+  display.setMarker('a', { lon: 0, lat: 0 });
+  display.setMarker('b', { lon: 1, lat: 0 });
+  const heights = () => {
+    const { positions } = engine.fake.moverSet('directions-markers').store;
+    return [0, 3].map(
+      (i) =>
+        geo.cartographic.fromCartesian({
+          x: positions[i],
+          y: positions[i + 1],
+          z: positions[i + 2],
+        }).height,
+    );
+  };
+  for (const height of heights()) near(height, 40, 'original terrain');
+  engine.fake.script('terrainHeight', 70);
+  await engine.maps.setTerrain({ kind: 'ellipsoid' });
+  engine.fake.frames(1);
+  for (const height of heights()) near(height, 70, 'replacement terrain');
+});

src/layers/infrastructure/render/display.js

@@ -17,6 +17,11 @@ import { bindOverlayHost } from '../../../overlays/bindOverlayHost.js';
 // surface. The references' cards go to the shared world-overlay host. A
 // click on any of them selects the feature and flies there.
 
+import {
+  createSurfacePoints,
+  readSurface,
+  surfaceTriggers,
+} from '../../../globe/surfacePlacement.js';
 import * as geo from '../../../geo/index.js';
 import { isPointerFree } from '../../../data/inputOwnership.js';
 import {
@@ -58,16 +63,7 @@ const FLY_SECONDS = 1.5;
  * sampled once and the base moves onto it.
  */
 export const GROUND_SAMPLE_MAX_DISTANCE_M = 75000;
-export const GROUND_SAMPLE_RETRY_MS = 2000;
 const GROUND_SAMPLE_MAX_ABS_HEIGHT_M = 9000;
-/**
- * A sampleable scene can still never answer under a feature; each retry
- * asks for the frame the next one needs, so after this many armed retries
- * without a newly grounded base the layer stops asking. A camera move, a
- * grounded base or sampling becoming supported again re-opens the budget.
- * 30 × 2 s is far longer than a tile stream-in.
- */
-export const GROUND_SAMPLE_MAX_ARMED_RETRIES = 30;
 /** Tip moves below this are camera noise and are not drawn. */
 export const LOCAL_STEM_TIP_EPSILON_M = 0.5;
 const TIP_EPSILON_SQ = LOCAL_STEM_TIP_EPSILON_M ** 2;
@@ -151,10 +147,7 @@ export function createInfrastructureDisplay(
   let dirty = true,
     lastWalk = Number.NEGATIVE_INFINITY,
     walkCount = 0;
-  // The ground-sample retry.
-  let retryTimer = null,
-    retryArms = 0,
-    lastCapability = null;
+  let surface = null;
   // Per walk: the view-projection matrix, computed on first use.
   const viewProjection = geo.matrix4.create();
   let viewProjectionWalk = -1;
@@ -165,23 +158,6 @@ export function createInfrastructureDisplay(
 
   const photoreal = () => engine.maps?.photorealActive?.() === true;
 
-  function scheduleGroundRetry() {
-    if (retryTimer || !dataset || !engine.surface.supported) return;
-    if (retryArms >= GROUND_SAMPLE_MAX_ARMED_RETRIES) return;
-    retryArms += 1;
-    retryTimer = setTimeout(() => {
-      retryTimer = null;
-      if (dataset && !destroyed) wake(`local-ground-retry:${id}`);
-    }, GROUND_SAMPLE_RETRY_MS);
-  }
-
-  function clearGroundRetry() {
-    retryArms = 0;
-    lastCapability = null;
-    clearTimeout(retryTimer);
-    retryTimer = null;
-  }
-
   /** The record's vertical at `height` metres above the ellipsoid. */
   function vertical(row, height, result) {
     scratchCarto.longitude = row.carto.longitude;
@@ -227,7 +203,7 @@ export function createInfrastructureDisplay(
   function groundInView(row) {
     const terrain = photoreal()
       ? undefined
-      : engine.surface.terrainHeight(row.carto);
+      : readSurface(engine, row.carto, { prefer: 'terrain' });
     const known =
       finite(terrain) && Math.abs(terrain) <= GROUND_SAMPLE_MAX_ABS_HEIGHT_M;
     const low = vertical(
@@ -262,53 +238,36 @@ export function createInfrastructureDisplay(
     row.baseMoved = true;
   }
 
-  // The scene height under the record, once, while the visible surface has
-  // loaded. A coarse sample can lie below the loaded terrain: the terrain is
-  // the floor then (not under photoreal tiles), while roofs and valid
-  // below-sea-level heights stay.
-  function sampleGround(row, now) {
-    if (row.groundSampled || !engine.surface.supported) return false;
-    if (now - row.lastSample < GROUND_SAMPLE_RETRY_MS) return false;
-    if (!groundInView(row)) return false;
-    row.lastSample = now;
-    const globe = !photoreal();
-    if (globe && !engine.surface.tilesLoaded()) return false;
-    // The stem stands on the sample point: out of the sample.
-    stemBatch?.show(false);
-    let sampled;
-    try {
-      sampled = engine.surface.sampleHeight(row.carto, exclude);
-    } finally {
-      stemBatch?.show(true);
-    }
-    if (!finite(sampled) || Math.abs(sampled) > GROUND_SAMPLE_MAX_ABS_HEIGHT_M)
-      return false;
-    const terrain = globe ? engine.surface.terrainHeight(row.carto) : undefined;
-    if (finite(terrain) && Math.abs(terrain) <= GROUND_SAMPLE_MAX_ABS_HEIGHT_M)
-      sampled = Math.max(sampled, terrain);
-    row.groundSampled = true;
-    setGroundHeight(row, sampled);
-    return true;
-  }
-
-  // A sampled base follows refined terrain upward on the bounded walks,
-  // without another sample.
-  function refreshTerrainFloor(row, camera) {
-    if (!row.groundSampled || photoreal() || !engine.surface.tilesLoaded())
-      return false;
-    if (
-      geo.cartesian3.distance(camera, row.base) >= GROUND_SAMPLE_MAX_DISTANCE_M
-    )
-      return false;
-    const height = engine.surface.terrainHeight(row.carto);
-    if (
-      !finite(height) ||
-      Math.abs(height) > GROUND_SAMPLE_MAX_ABS_HEIGHT_M ||
-      height <= row.groundHeight
-    )
-      return false;
-    setGroundHeight(row, height);
-    return true;
+  function placeGround() {
+    const points = [...rows.values()];
+    surface = createSurfacePoints(engine, {
+      groups: () => {
+        viewProjectionWalk = -1;
+        return [
+          {
+            points: points.map((row) => row.surface),
+            exclude: [...exclude, stemBatch].filter(Boolean),
+            set: {
+              set(index, { position }) {
+                const row = points[index];
+                setGroundHeight(
+                  row,
+                  geo.cartographic.fromCartesian(position).height,
+                );
+              },
+              commit() {
+                dirty = true;
+                lastWalk = Number.NEGATIVE_INFINITY;
+              },
+            },
+          },
+        ];
+      },
+      // The LOD checks the entire ground vertical before offering a point.
+      screenMargin: Infinity,
+      prefer: 'sceneFloor',
+      request: wake,
+    });
   }
 
   // The tip STEM_TARGET_PX above the base at the camera's distance; a move
@@ -317,7 +276,6 @@ export function createInfrastructureDisplay(
     const distance = finite(knownDistance)
       ? knownDistance
       : geo.cartesian3.distance(pose.position, row.base);
-    if (distance < GROUND_SAMPLE_MAX_DISTANCE_M) sampleGround(row, now);
     const tipHeight =
       row.groundHeight +
       Math.max(distance, 1) *
@@ -395,6 +353,9 @@ export function createInfrastructureDisplay(
       nowMs: now,
       activeLimit: selection.budget.activeLimit,
     });
+    for (const id of kept.keepIds)
+      if (!active.has(id) || rows.get(id).surface.surfaceHeight === undefined)
+        delete rows.get(id).surface.surfaceRevision;
     active = new Set(kept.keepIds);
     grace = kept.graceState;
     budget = selection.budget.activeLimit;
@@ -433,20 +394,18 @@ export function createInfrastructureDisplay(
       if (probe.recompute) dirty = true;
     }
     const refresh = dirty;
-    // Without sampling no retry is armed and no per-record work is spent.
-    const canSample = engine.surface.supported === true;
-    // Sampling that comes back re-opens a spent budget on a parked camera.
-    if (canSample && lastCapability === false) retryArms = 0;
-    lastCapability = canSample;
-    let retryPending = false;
-    let grounded = false;
     if (refresh && rows.size) selectLod(pose, now);
+    surface.place();
     let tipsChanged = false;
     let pinsChanged = false;
     const visible = [];
     for (const row of rows.values()) {
       const isActive = !computed || active.has(row.id);
-      const isVisible = isActive && engine.projector.horizonVisible(row.base);
+      const isVisible =
+        isActive &&
+        engine.projector.horizonVisible(
+          vertical(row, Math.max(0, row.groundHeight), scratchLow),
+        );
       if (row.show !== isVisible) {
         row.show = isVisible;
         tips.set(row.index, { show: isVisible });
@@ -458,30 +417,7 @@ export function createInfrastructureDisplay(
       }
       if (!isVisible) dropStem(row.id);
       if (!isActive) continue;
-      const wasSampled = row.groundSampled;
-      const floorChanged = refreshTerrainFloor(row, camera);
-      if (refresh || floorChanged) sizeStem(row, now, pose, view);
-      else if (
-        canSample &&
-        !row.groundSampled &&
-        now - row.lastSample >= GROUND_SAMPLE_RETRY_MS
-      ) {
-        const distance = geo.cartesian3.distance(camera, row.base);
-        if (distance < GROUND_SAMPLE_MAX_DISTANCE_M && sampleGround(row, now))
-          sizeStem(row, now, pose, view, distance);
-      }
-      if (!wasSampled && row.groundSampled) grounded = true;
-      // An ungrounded base in range and in view: the retry needs a frame
-      // the idle governor would never produce.
-      if (
-        canSample &&
-        !row.groundSampled &&
-        !retryPending &&
-        geo.cartesian3.distance(camera, row.base) <
-          GROUND_SAMPLE_MAX_DISTANCE_M &&
-        groundInView(row)
-      )
-        retryPending = true;
+      if (refresh || row.baseMoved) sizeStem(row, now, pose, view);
       if (row.tipMoved) {
         row.tipMoved = false;
         tips.set(row.index, { position: row.tip });
@@ -521,9 +457,6 @@ export function createInfrastructureDisplay(
     dirty = false;
     if (tipsChanged) tips.commit();
     if (pinsChanged) pins.commit();
-    // Real progress re-opens the budget for the records still waiting.
-    if (grounded) retryArms = 0;
-    if (retryPending) scheduleGroundRetry();
     publisher.publish(
       selectLocalInfrastructureOverlayCohort(visible, {
         maxEntries: labelMax,
@@ -575,7 +508,8 @@ export function createInfrastructureDisplay(
   function hide() {
     const shown = Boolean(dataset);
     services.hideOsmCredit?.(engine, id);
-    clearGroundRetry();
+    surface?.destroy();
+    surface = null;
     for (const remove of removers.splice(0)) remove();
     stems.clear();
     stemBatch?.destroy();
@@ -640,8 +574,6 @@ export function createInfrastructureDisplay(
         nextTip: geo.cartesian3.clone(tip),
         priority,
         groundHeight: 0,
-        groundSampled: false,
-        lastSample: Number.NEGATIVE_INFINITY,
         // As a Cesium entity's: shown until the first walk decides; the
         // context store reads it (isContextRecordActive).
         show: true,
@@ -659,6 +591,19 @@ export function createInfrastructureDisplay(
           : null,
       };
       row.__localBaseCartesian = row.base;
+      row.surface = {
+        cartographic: carto,
+        position: base,
+        get show() {
+          return (
+            (photoreal() || engine.surface.tilesLoaded()) &&
+            (!computed || active.has(row.id)) &&
+            geo.cartesian3.distance(engine.camera.livePosition, row.base) <
+              GROUND_SAMPLE_MAX_DISTANCE_M &&
+            groundInView(row)
+          );
+        },
+      };
       rows.set(row.id, row);
       services.registerEntityContext?.(row, {
         id: row.pickId,
@@ -741,15 +686,14 @@ export function createInfrastructureDisplay(
       try {
         dataset = next;
         build(next);
+        placeGround();
         removers.push(
-          engine.frames.preRender.addEventListener(walk),
-          engine.camera.moveEnd.addEventListener(() => {
+          surfaceTriggers(engine, () => {
             dirty = true;
             lastWalk = Number.NEGATIVE_INFINITY;
-            // A camera move is a fresh situation with free frames.
-            retryArms = 0;
             wake();
           }),
+          engine.frames.preRender.addEventListener(walk),
           engine.input.on('click', onClick, { pick: true }),
         );
         publisher.show();

src/layers/infrastructure/render/display.test.mjs

@@ -21,7 +21,6 @@ import {
 import { LOCAL_OVERLAY_COHORT_LIMIT } from '../../../data/localGeojsonCore.js';
 import { rgbaFromCss } from '../../shared/color.js';
 import {
-  GROUND_SAMPLE_MAX_ARMED_RETRIES,
   LOCAL_STEM_TIP_EPSILON_M,
   createInfrastructureDisplay,
 } from './display.js';
@@ -380,15 +379,6 @@ function fixture(t, makeHarness, { config = DAMS, surface = {} } = {}) {
   };
 }
 
-/** Each walk arms a timer, the timer asks for a frame, the frame walks. */
-function runArmedRetryChain(f, t, clock, cycles) {
-  for (let i = 0; i < cycles; i++) {
-    f.preRender();
-    clock.advance(2_100);
-    t.mock.timers.tick(2_100);
-  }
-}
-
 /** The camera `southM` south of the dam at `cameraM`, aimed at `groundM`. */
 function aim(f, { groundM, cameraM, southM, away = false }) {
   const lat = DAM_LAT - geo.math.toDegrees(southM / 6_371_000);
@@ -677,7 +667,8 @@ for (const makeHarness of HARNESSES) {
     // Looking away from the dam.
     aim(f, { groundM: 117, cameraM: 20_000, southM: 5_000, away: true });
     f.display.show(dataset([DAM]));
-    runArmedRetryChain(f, t, clock, 5);
+    clock.advance(10_500);
+    f.preRender();
     assert.equal(f.sampleCalls(), 0, 'an off-screen base is not sampled');
     assert.equal(f.retries(), 0, 'nor keeps a parked camera rendering');
     // In view but over the horizon: 50 m up, about 67 km away.
@@ -687,7 +678,8 @@ for (const makeHarness of HARNESSES) {
       roll: 0,
     });
     f.moveEnd();
-    runArmedRetryChain(f, t, clock, 5);
+    clock.advance(10_500);
+    f.preRender();
     assert.equal(f.sampleCalls(), 0, 'a base over the horizon is not sampled');
     assert.equal(f.retries(), 0);
     f.look(DAM_LON, DAM_LAT, 20_000);
@@ -814,10 +806,10 @@ for (const makeHarness of HARNESSES) {
     clock.advance(500);
     f.preRender();
     assert.ok(
-      Math.abs(f.baseHeight() - 120) < 0.01,
-      'terrain under photoreal tiles is not a floor',
+      Math.abs(f.baseHeight() - 117) < 0.01,
+      'switching surfaces places the base on the mesh',
     );
-    assert.equal(f.sampleCalls(), 1, 'one sample in all');
+    assert.equal(f.sampleCalls(), 3, 'one sample per changed surface');
   });
 
   for (const [terrainHeight, sampledHeight, expectedHeight, photoreal] of [
@@ -845,153 +837,65 @@ for (const makeHarness of HARNESSES) {
       );
     });
 
-  test(`the stem is out of the scene while its ground is sampled (${name})`, (t) => {
-    let fails = true;
-    const f = fixture(t, makeHarness, {
-      surface: {
-        supported: true,
-        sample: () => (fails ? undefined : 50),
-        terrain: () => 0,
-      },
-    });
-    const clock = installFakeClock(t);
-    f.look(DAM_LON, DAM_LAT, 20_000);
-    f.display.show(dataset([DAM]));
-    f.preRender();
-    fails = false;
-    clock.advance(2_100);
-    f.preRender();
-    assert.deepEqual(f.line(f.stemId('real-dam')).shows, [false, true]);
-    assert.ok(Math.abs(f.baseHeight() - 50) < 0.01);
-  });
-
-  test(`a failed ground sample schedules the retry frame the idle governor would not (${name})`, (t) => {
-    const f = fixture(t, makeHarness, {
-      surface: { supported: true, terrain: () => 0 },
-    });
-    t.mock.timers.enable({ apis: ['setTimeout'] });
-    f.look(DAM_LON, DAM_LAT, 20_000);
-    f.display.show(dataset([DAM]));
-    f.preRender();
-    assert.equal(f.retries(), 0, 'deferred by the retry window');
-    t.mock.timers.tick(2_100);
-    assert.ok(f.requests.includes('local-ground-retry:local-dams'));
-  });
-
-  test(`a far camera arms no retry (${name})`, (t) => {
-    const f = fixture(t, makeHarness, {
-      surface: { supported: true, terrain: () => 0 },
-    });
-    t.mock.timers.enable({ apis: ['setTimeout'] });
-    f.look(DAM_LON, DAM_LAT, 400_000);
-    f.display.show(dataset([DAM]));
-    f.preRender();
-    t.mock.timers.tick(5_000);
-    assert.equal(f.retries(), 0);
-  });
-
-  test(`hide cancels a pending retry (${name})`, (t) => {
-    const f = fixture(t, makeHarness, {
-      surface: { supported: true, terrain: () => 0 },
-    });
-    t.mock.timers.enable({ apis: ['setTimeout'] });
-    f.look(DAM_LON, DAM_LAT, 20_000);
-    f.display.show(dataset([DAM]));
-    f.preRender();
-    f.display.hide();
-    t.mock.timers.tick(5_000);
-    assert.equal(f.retries(), 0);
-  });
-
-  test(`a scene that cannot sample never samples and never arms (${name})`, (t) => {
-    const f = fixture(t, makeHarness, {
-      surface: { supported: false, sample: () => 117, terrain: () => 0 },
-    });
-    t.mock.timers.enable({ apis: ['setTimeout'] });
-    const clock = installFakeClock(t);
-    f.look(DAM_LON, DAM_LAT, 20_000);
-    f.display.show(dataset([DAM]));
-    f.preRender();
-    clock.advance(2_100);
-    runArmedRetryChain(f, t, clock, 5);
-    assert.equal(f.retries(), 0);
-    assert.equal(f.sampleCalls(), 0);
-    assert.ok(Math.abs(f.baseHeight()) < 1e-6, 'bases stay on the ellipsoid');
-  });
-
-  test(`a sampleable scene keeps trying (${name})`, (t) => {
-    const f = fixture(t, makeHarness, {
-      surface: { supported: true, terrain: () => 0 },
-    });
-    t.mock.timers.enable({ apis: ['setTimeout'] });
-    const clock = installFakeClock(t);
-    f.look(DAM_LON, DAM_LAT, 20_000);
-    f.display.show(dataset([DAM]));
-    runArmedRetryChain(f, t, clock, 5);
-    assert.equal(f.sampleCalls(), 5);
-  });
-
-  test(`sampling that comes back re-opens a spent budget without camera motion (${name})`, (t) => {
-    let supported = true;
-    const f = fixture(t, makeHarness);
-    const setSurface = () =>
-      f.surface({ supported, terrain: () => 0, tilesLoaded: () => true });
-    setSurface();
-    t.mock.timers.enable({ apis: ['setTimeout'] });
-    const clock = installFakeClock(t);
-    f.look(DAM_LON, DAM_LAT, 20_000);
-    f.display.show(dataset([DAM]));
-    runArmedRetryChain(f, t, clock, GROUND_SAMPLE_MAX_ARMED_RETRIES + 2);
-    assert.equal(f.retries(), GROUND_SAMPLE_MAX_ARMED_RETRIES, 'budget spent');
-    supported = false;
-    setSurface();
-    runArmedRetryChain(f, t, clock, 2);
-    assert.equal(f.retries(), GROUND_SAMPLE_MAX_ARMED_RETRIES);
-    supported = true;
-    setSurface();
-    runArmedRetryChain(f, t, clock, 3);
-    assert.equal(f.retries(), GROUND_SAMPLE_MAX_ARMED_RETRIES + 3);
-  });
-
-  test(`a scene that keeps failing gives up after a bounded run of arms (${name})`, (t) => {
-    const f = fixture(t, makeHarness, {
-      surface: { supported: true, terrain: () => 0 },
-    });
-    t.mock.timers.enable({ apis: ['setTimeout'] });
-    const clock = installFakeClock(t);
-    f.look(DAM_LON, DAM_LAT, 20_000);
-    f.display.show(dataset([DAM]));
-    runArmedRetryChain(f, t, clock, GROUND_SAMPLE_MAX_ARMED_RETRIES);
-    assert.equal(f.retries(), GROUND_SAMPLE_MAX_ARMED_RETRIES);
-    runArmedRetryChain(f, t, clock, 10);
-    assert.equal(f.retries(), GROUND_SAMPLE_MAX_ARMED_RETRIES, 'stops arming');
-  });
-
-  test(`after the cap a camera move still samples and re-opens the budget (${name})`, (t) => {
-    let height;
+  test(`the stem is excluded when a changed surface is sampled (${name})`, (t) => {
+    let height = 50;
     const f = fixture(t, makeHarness, {
       surface: { supported: true, sample: () => height, terrain: () => 0 },
     });
-    t.mock.timers.enable({ apis: ['setTimeout'] });
-    const clock = installFakeClock(t);
+    installFakeClock(t);
     f.look(DAM_LON, DAM_LAT, 20_000);
     f.display.show(dataset([DAM]));
-    runArmedRetryChain(f, t, clock, GROUND_SAMPLE_MAX_ARMED_RETRIES + 3);
-    assert.equal(f.retries(), GROUND_SAMPLE_MAX_ARMED_RETRIES);
-    assert.ok(Math.abs(f.baseHeight()) < 1e-6);
-    height = 210;
-    f.look(DAM_LON, DAM_LAT, 19_000);
-    f.moveEnd();
-    clock.advance(2_100);
     f.preRender();
-    assert.ok(Math.abs(f.baseHeight() - 210) < 1e-6, 'the move grounds it');
-    runArmedRetryChain(f, t, clock, 5);
+    height = 70;
+    f.moveEnd();
+    f.preRender();
+    const call = f.engine.fake.callsOf('surface.sampleHeight').at(-1);
     assert.equal(
-      f.retries(),
-      GROUND_SAMPLE_MAX_ARMED_RETRIES,
-      'a grounded record asks for nothing',
+      call.args[1].length,
+      2,
+      'both the tips and the stem batch are excluded',
     );
+    assert.ok(Math.abs(f.baseHeight() - 70) < 0.01);
   });
+
+  for (const trigger of ['moveEnd', 'tilesLoaded', 'terrainRevision']) {
+    test(`infrastructure follows ${trigger} and stops requesting idle frames (${name})`, async (t) => {
+      let height;
+      let loaded = true;
+      const f = fixture(t, makeHarness, {
+        surface: {
+          supported: true,
+          sample: () => height,
+          terrain: () => undefined,
+          tilesLoaded: () => loaded,
+        },
+      });
+      installFakeClock(t);
+      f.look(DAM_LON, DAM_LAT, 20_000);
+      f.display.show(dataset([DAM]));
+      f.preRender();
+      assert.ok(Math.abs(f.baseHeight()) < 0.01);
+      height = 210;
+      if (trigger === 'moveEnd') f.moveEnd();
+      if (trigger === 'tilesLoaded') {
+        loaded = false;
+        f.preRender();
+        loaded = true;
+      }
+      if (trigger === 'terrainRevision')
+        await f.engine.maps.setTerrain({ kind: 'ellipsoid' });
+      f.preRender();
+      assert.ok(Math.abs(f.baseHeight() - 210) < 0.01);
+      const requests = f.requests.length;
+      f.preRender();
+      f.preRender();
+      assert.equal(f.requests.length, requests);
+      f.display.hide();
+      f.moveEnd();
+      f.preRender();
+      assert.equal(f.engine.movers.list().length, 0);
+    });
+  }
 }
 
 // 150 polygons near Austin; the even ones are named (high label priority).

src/layers/streetLevel/view.js

@@ -1,3 +1,4 @@
+import { readSurface } from '../../globe/surfacePlacement.js';
 // What Street Level reads of the camera and the ground, on the globe
 // contract: `view` is the layer's display (render/display.js), whose
 // `engine` it asks. Screen rays meet an ellipsoid raised to the ground
@@ -43,25 +44,12 @@ export function plausibleSurfaceHeight(height) {
  * underground before tiles load).
  */
 export function sampledSurfaceHeight(engine, carto) {
-  let height = null;
-  try {
-    if (engine?.surface?.supported) height = engine.surface.sampleHeight(carto);
-  } catch {
-    /* not sampleable yet */
-  }
-  return plausibleSurfaceHeight(height) ? height : null;
+  return readSurface(engine, carto, { prefer: 'tiles' }) ?? null;
 }
 
 /** Height (m) of the terrain at `carto`, or null. */
 export function terrainSurfaceHeight(engine, carto) {
-  let height;
-  try {
-    if (engine?.surface?.terrainHeightSupported)
-      height = engine.surface.terrainHeight(carto);
-  } catch {
-    height = undefined;
-  }
-  return Number.isFinite(height) ? height : null;
+  return readSurface(engine, carto, { prefer: 'terrain' }) ?? null;
 }
 
 /**

src/layers/traffic/ingestion.js

@@ -1,3 +1,4 @@
+import { readSurface } from '../../globe/surfacePlacement.js';
 import * as geo from '../../geo/index.js';
 import { requestWithDeadline } from '../../sources/requestDeadline.js';
 import {
@@ -280,14 +281,11 @@ export function createIngestion({
     let estimated = services.ground?.cachedGroundFloor?.(centerLat, centerLon);
     if (!Number.isFinite(estimated) && engine) {
       try {
-        estimated = !engine.maps.photorealActive()
-          ? engine.surface.terrainHeight(location)
-          : engine.surface.supported
-            ? engine.surface.sampleHeight(
-                location,
-                layerState._display?.excluded() ?? [],
-              )
-            : undefined;
+        estimated = readSurface(engine, location, {
+          exclude: layerState._display?.excluded() ?? [],
+          prefer: engine.maps.photorealActive() ? 'tiles' : 'terrain',
+          minHeight: -9000,
+        });
       } catch {
         /* the local mesh can still be loading */
       }

src/layers/traffic/surface.js

@@ -1,3 +1,4 @@
+import { readSurface } from '../../globe/surfacePlacement.js';
 import { phaseTiming } from '../../sources/phaseTiming.js';
 import * as geo from '../../geo/index.js';
 import { DOT_HEIGHT_OFFSET, MAX_WAYPOINTS_PER_ROAD } from './policy.js';
@@ -303,7 +304,11 @@ export async function prepareRoadSurfaces(
         // locally rendered mesh, not unresolved/offscreen tiles: global
         // tilesLoaded can stay false while this street is usable.
         const photoreal = engine.maps.photorealActive();
-        if (!photoreal) sampled = engine.surface.terrainHeight(carto);
+        if (!photoreal)
+          sampled = readSurface(engine, carto, {
+            prefer: 'terrain',
+            minHeight: -9000,
+          });
         else {
           const estimate = geo.cartographic.fromCartesian(
             road.waypoints[i],
@@ -311,11 +316,15 @@ export async function prepareRoadSurfaces(
           sampled = renderedRoadHeight(engine, lon, lat, estimate);
           if (validHeight(sampled)) metrics.depthHits++;
         }
-        if (photoreal && !validHeight(sampled) && engine.surface.supported) {
+        if (photoreal && !validHeight(sampled)) {
           const sampleStart = performance.now();
           metrics.sampleCount++;
           try {
-            sampled = engine.surface.sampleHeight(carto, excluded);
+            sampled = readSurface(engine, carto, {
+              exclude: excluded,
+              prefer: 'tiles',
+              minHeight: -9000,
+            });
           } catch {
             /* local mesh missing */
           }

src/layers/transit/lifecycle.test.mjs

@@ -3715,32 +3715,30 @@ test('actual Traffic, Bikeshare and Transit lifecycles retain sensitivity in eve
     },
   }).methods;
   // The bikeshare display claims through its engine's camera: the viewer's.
-  const bike = createBikeshareDisplay(
-    { camera: app.viewer.camera },
-    {
-      state: {
-        _overlayHost: { setVisible: noop },
-        _cityRuntime: new Map(),
-        _failedCityIds: new Set(),
-      },
-      services: {
-        render: { governorRequestRender: noop },
-        picking: { registerPickOwner: noop, unregisterPickOwner: noop },
-      },
-      source: {},
-      parts: {
-        display: {
-          _installClickHandler: noop,
-          _uninstallClickHandler: noop,
-          _clearSelection: noop,
-          onCameraChanged: noop,
-          runProximityCheck: noop,
-          deactivateAllCities: noop,
-        },
-        ingestion: { abortAllInFlight: noop },
-      },
+  const bike = createBikeshareDisplay(app.engine, {
+    state: {
+      _stationRenderMap: new Map(),
+      _overlayHost: { setVisible: noop },
+      _cityRuntime: new Map(),
+      _failedCityIds: new Set(),
     },
-  );
+    services: {
+      render: { governorRequestRender: noop },
+      picking: { registerPickOwner: noop, unregisterPickOwner: noop },
+    },
+    source: {},
+    parts: {
+      display: {
+        _installClickHandler: noop,
+        _uninstallClickHandler: noop,
+        _clearSelection: noop,
+        onCameraChanged: noop,
+        runProximityCheck: noop,
+        deactivateAllCities: noop,
+      },
+      ingestion: { abortAllInFlight: noop },
+    },
+  });
   const layers = { traffic, bikeshare: bike, transit: app.layer };
   const orders = [
     ['traffic', 'bikeshare', 'transit'],

src/layers/transit/render/display.js

@@ -1,3 +1,4 @@
+import { readSurface } from '../../../globe/surfacePlacement.js';
 // The transit vehicles on the globe contract, the same on every engine:
 // - markers: two engine.movers sprite sets (the stationary fleet and the
 //   vehicles mid-glide, so a glide never rewrites the fleet), drawn over the
@@ -708,9 +709,10 @@ export function createTransitDisplay(
       // Photoreal tiles hide the globe: the floor comes from the mesh
       // samples and the coarse floors instead.
       if (engine.maps.photorealActive()) return undefined;
-      if (!engine.surface.terrainHeightSupported) return undefined;
-      return engine.surface.terrainHeight(
+      return readSurface(
+        engine,
         geo.cartographic.fromDegrees(lon, lat, 0, scratchCartographic),
+        { prefer: 'terrain' },
       );
     },
     // The engine's surface leaves out mover sets, not single sprites: a

src/layers/wildlifeSightings/ownership.test.mjs

@@ -296,7 +296,7 @@ function harness(
     /** Listeners that run on every drawn frame. */
     frameWork: () => engine.frames.preRender.numberOfListeners,
     /** The surface-loading watch (one per enabled scene). */
-    surfaceWatch: () => engine.frames.postRender.numberOfListeners,
+    surfaceWatch: () => engine.frames.preRender.numberOfListeners,
     /** Surface loading as the engine reports it, then one frame. */
     tiles(loaded) {
       tilesLoaded = loaded;
@@ -370,16 +370,16 @@ test('terrain warming resamples unchanged point, card and context anchors withou
   h.moveEnd.emit();
   assert.equal(
     samples,
-    before,
-    'unchanged snapshots and camera movement do not resample per point',
+    before + 1,
+    'camera rest resamples the land anchor once',
   );
   h.tiles(false);
-  assert.equal(samples, before, 'wait for terrain loading to settle');
+  assert.equal(samples, before + 1, 'wait for terrain loading to settle');
   h.tiles(true);
   assert.ok(Math.abs(cartographicOf(point.position).height - 600) < 0.01);
   assert.equal(
     samples,
-    before + 1,
+    before + 2,
     'Acartia sea anchors are never terrain-sampled',
   );
   assert.ok(Math.abs(cartographicOf(sea.position).height) < 0.01);
@@ -403,7 +403,7 @@ test('terrain warming resamples unchanged point, card and context anchors withou
     point.position,
   );
   assert.ok(h.renders.includes('wildlife-sightings-terrain'));
-  assert.equal(h.frameWork(), 0);
+  assert.equal(h.frameWork(), 1);
   h.layer.disable();
   assert.equal(h.surfaceWatch(), 0);
   const disabledSamples = samples;
@@ -864,7 +864,7 @@ test('privacy cells draw on ground, replace changed batches and release them', a
   await h.update();
   const first = cells();
   assert.equal(h.engine.ground.list().length, 1);
-  assert.equal(h.frameWork(), 0, 'static cells need no frame work');
+  assert.equal(h.frameWork(), 1, 'only the shared surface observer');
   rows = [{ ...rows[0], iconic: 'Fungi' }];
   await h.update();
   const second = cells();
@@ -1636,7 +1636,7 @@ test('ambient cards prefilter the horizon, spread over screen regions and retain
   assertCohort(entries);
   const farDot = h.badges().find((point) => point.id === 'wildlife:inat:far');
   assert.ok(!farDot || farDot.show === false);
-  assert.equal(h.frameWork(), 0);
+  assert.equal(h.frameWork(), 1);
   h.layer.selectSighting('inat:01');
   const selected = h.overlay.entries.get('wildlife-sightings-selected');
   h.moveEnd.emit();
@@ -1680,7 +1680,7 @@ test('observations publish real badges while grid acquisition is still pending',
     await new Promise((resolve) => setImmediate(resolve));
     assert.equal(h.badges()[0]?.id, 'wildlife:inat:1');
     assert.equal(h.layer.getStats().count, 1);
-    assert.equal(h.frameWork(), 0, 'acquisition adds no frame work');
+    assert.equal(h.frameWork(), 1, 'only the shared surface observer');
   } finally {
     finishGrid({ cells: [], totalResults: 0, fetchedAt: NOW });
     await updating;
@@ -1733,7 +1733,7 @@ test('each arriving tile extends the density glow before the remaining tiles fin
     assert.equal(h.badges().length, 0);
     assert.equal(h.glow().store.count, 2);
     assert.equal(h.layer.getStats().countLabel, '21 sightings in view');
-    assert.equal(h.frameWork(), 1, 'only the glow follows the camera');
+    assert.equal(h.frameWork(), 2, 'glow and the shared surface observer');
   } finally {
     finishGrid({ cells, totalResults: 21, fetchedAt: NOW });
     await updating;
@@ -1767,7 +1767,7 @@ test('grid-only views draw nonpickable glow without observation badges, labels o
   assert.deepEqual(h.overlay.entries.get('wildlife-sightings-labels'), []);
   assert.deepEqual(h.overlay.entries.get('wildlife-sightings-selected'), []);
   assert.equal(h.focus.length, 0);
-  assert.equal(h.frameWork(), 1, 'only the glow follows the camera');
+  assert.equal(h.frameWork(), 2, 'glow and the shared surface observer');
   h.layer.disable();
   assert.equal(h.glow(), undefined);
   assert.equal(h.frameWork(), 0);
@@ -2008,7 +2008,7 @@ test('label candidates are bounded after on-screen and horizon filtering, with n
       (entry) => cartographicOf(entry.position).latitude < toRadians(47.59),
     ),
   );
-  assert.equal(h.frameWork(), 0);
+  assert.equal(h.frameWork(), 1);
   h.layer.destroy();
 });
 

src/layers/wildlifeSightings/rendering.js

@@ -1,3 +1,4 @@
+import { surfaceTriggers } from '../../globe/surfacePlacement.js';
 import * as geo from '../../geo/index.js';
 import { rgbaFromCss } from '../shared/color.js';
 import { SPRITE_LAYER_ORDER } from '../../data/spriteOrder.js';
@@ -260,14 +261,7 @@ export function createRendering({ state, services, parts }) {
     refreshBadgeImages();
     // The ground floor cache warms as tiles arrive: resample once the
     // surface has settled, on the frame after loading ends.
-    let loaded = engine.surface.tilesLoaded();
-    surfaceRemovers.push(
-      engine.frames.postRender.addEventListener(() => {
-        const now = engine.surface.tilesLoaded();
-        if (now && !loaded) resampleAnchors();
-        loaded = now;
-      }),
-    );
+    surfaceRemovers.push(surfaceTriggers(engine, resampleAnchors));
     // Terrain, tileset and imagery changes all go through the map stack.
     services.eventTarget?.addEventListener?.(
       'gev:map-stack-changed',

src/layers/wildlifeSightings/rendering.test.mjs

@@ -187,12 +187,12 @@ test('badge sprites update in place, and unchanged refreshes write nothing', ()
   assert.equal(h.counts.created, 3);
   assert.equal(h.counts.removed, 1);
   assert.equal(h.counts.cleared, 0);
-  assert.equal(h.engine.frames.postRender.numberOfListeners, 1);
+  assert.equal(h.engine.frames.preRender.numberOfListeners, 1);
   h.rendering.destroy();
   assert.equal(h.badges(), undefined);
   assert.deepEqual(h.engine.movers.list(), []);
   assert.equal(h.state.pointById.size, 0);
-  assert.equal(h.engine.frames.postRender.numberOfListeners, 0);
+  assert.equal(h.engine.frames.preRender.numberOfListeners, 0);
 });
 
 test('horizon changes write only changed visibility, with one governor request per batch', () => {
@@ -349,8 +349,8 @@ test('sampled fallback buckets allocate only representatives at every height, wi
     assert.deepEqual(h.counts.writes, []);
     assert.equal(
       h.engine.frames.preRender.numberOfListeners,
-      0,
-      'badges need no frame work',
+      1,
+      'one shared surface observer',
     );
     h.rendering.destroy();
   }
@@ -384,8 +384,8 @@ test('UTFGrid creates a dedicated unpickable glow and observations alone create
   );
   assert.equal(
     h.engine.frames.preRender.numberOfListeners,
-    1,
-    'metre-sized glow follows the camera',
+    2,
+    'glow and the shared surface observer follow the camera',
   );
   const glowSet = h.rendering.density.collection.set;
   h.state.gridCells = [...h.state.gridCells].reverse();
@@ -396,7 +396,7 @@ test('UTFGrid creates a dedicated unpickable glow and observations alone create
   h.rendering.clear();
   assert.equal(glowSet.isDestroyed(), true);
   assert.equal(h.glow(), undefined);
-  assert.equal(h.engine.frames.preRender.numberOfListeners, 0);
+  assert.equal(h.engine.frames.preRender.numberOfListeners, 1);
   assert.equal(h.badges().store.count, 0);
   h.rendering.destroy();
   assert.deepEqual(h.engine.movers.list(), []);

src/services/groundSnap.js

@@ -1,3 +1,4 @@
+import { readSurface } from '../globe/surfacePlacement.js';
 /**
  * groundSnap.js — one-shot cached ground-height snap for MODELED grounded aircraft.
  *
@@ -47,7 +48,6 @@
  */
 
 import * as geo from '../geo/index.js';
-import { acceptedSurfaceHeight } from '../globe/surfaceDetail.js';
 import { MAX_FLOOR_TILE_SIZE_M } from './meshFloorSampler.js';
 
 /** Taxi threshold: a cached snap answers directly for moves up to this far from
@@ -352,10 +352,11 @@ export function createGroundSnap({ groundFloor }) {
       // sampleHeight throws when unsupported (no depth textures) — that's a miss.
       const exclusions = getExclusions ? getExclusions() : undefined;
       // A coarse tile's answer, or only terrain, is a miss.
-      sampled = acceptedSurfaceHeight(
-        engine.surface.sampleHeightDetailed(carto, { exclude: exclusions }),
-        { maxTileSizeM: MAX_FLOOR_TILE_SIZE_M },
-      );
+      sampled = readSurface(engine, carto, {
+        exclude: exclusions,
+        prefer: 'tiles',
+        maxTileSizeM: MAX_FLOOR_TILE_SIZE_M,
+      });
     } catch {
       sampled = undefined;
     }

src/services/meshFloorSampler.js

@@ -1,5 +1,5 @@
+import { readSurface } from '../globe/surfacePlacement.js';
 import * as geo from '../geo/index.js';
-import { acceptedSurfaceHeight } from '../globe/surfaceDetail.js';
 
 /** Answers from tiles larger than this are too coarse to latch (m).
  *  Measured on Navara: from 800 m the answering tiles were 112-314 m and
@@ -158,12 +158,11 @@ export function createMeshFloorSampler({
           _scratchEngineProbe,
         );
         // A coarse tile's answer, or only terrain, is a miss (no latch).
-        height = acceptedSurfaceHeight(
-          engine.surface.sampleHeightDetailed(carto, {
-            exclude: excludeObjects,
-          }),
-          { maxTileSizeM: MAX_FLOOR_TILE_SIZE_M },
-        );
+        height = readSurface(engine, carto, {
+          exclude: excludeObjects,
+          prefer: 'tiles',
+          maxTileSizeM: MAX_FLOOR_TILE_SIZE_M,
+        });
         sampled += 1;
       } catch {
         continue; // scene mid-teardown — try again next poll

src/ui/cockpitHost.js

@@ -1,3 +1,4 @@
+import { readSurface } from '../globe/surfacePlacement.js';
 // Camera and aircraft ownership used by the shared first-person controller,
 // on the globe contract: the ridden aircraft is the engine follow's target,
 // the aircraft display's tracked glyph handle.
@@ -26,7 +27,7 @@ export function cockpitHost(engine, { viewer = null } = {}) {
     restore: (target) => target.resumeAircraftFollow(),
     camera: engine.camera,
     cartographic: () => engine.camera.pose().cartographic,
-    terrainHeight: (place) => engine.surface.terrainHeight(place),
+    terrainHeight: (place) => readSurface(engine, place, { prefer: 'terrain' }),
     surface: engine,
     pick: (position) => engine.picker.pick(position),
     // A full mesh read is still Cesium's; the contract's detailed read is

src/ui/geoFileImport.js

@@ -469,7 +469,6 @@ export function createGeoFileImport({
       engine,
       controller: new AbortController(),
     });
-    ownEvent(engine.camera.moveEnd, ground);
     const container = engine.host.container;
     const canvas = engine.host.canvas || container;
     listen(canvas, 'pointerdown', gesture, { passive: true });

src/ui/geoFileImport.test.mjs

@@ -755,7 +755,7 @@ test('what no engine draws of a file is reported, and the drawing follows the en
   assert.match(t.shown().hint, /leaves out of a\.kml: 3/);
   assert.ok(engine.host.canvas.listeners.length > 0, 'gestures on its canvas');
   assert.ok(engine.host.container.listeners.length > 0, 'drops on it');
-  assert.equal(engine.moveEnd.size, 1);
+  assert.equal(engine.moveEnd.size, 0);
   const [a] = rows(t);
   press(t, a, 'toggle');
   assert.equal(t.added.at(-1).show, false);