docs(performance): cables rewrite in #1722 and clouds shader in #1721

Co-Authored-By: Claude Fable 5.2 <[email protected]>

changelog.d/1705-traffic-road-load.md

@@ -1,4 +0,0 @@
-- Cut the stutter while zooming and panning with Street Traffic on in dense
-  cities. Coarse roads are no longer clipped against every detail tile in one
-  task, roads already parsed in a load are not parsed again, and ground floors
-  are read once per cell (mazy1998, #1705).

docs/PERFORMANCE-AUDIT-2026-11.md

@@ -0,0 +1,322 @@
+# Slowdown audit, November 2026
+
+A sweep of `main` (`c02ede3bb`, 13 November 2026) for bugs that freeze the page
+or hold the frame rate down. This page lists what was found, why it happens and
+how to fix it, and names the pull request that carries each fix.
+
+[PERFORMANCE.md](PERFORMANCE.md) is the measured baseline of a healthy build;
+this page is the list of things that fall outside it.
+
+## How it was measured
+
+- Keyless dev server, headless Chrome at 1440 x 900 on Apple silicon (Metal
+  through ANGLE), default globe map.
+- Per scenario: load, a spell at rest, scripted drags and wheel zooms, then a
+  settle. Long tasks were counted with a `PerformanceObserver`, the hot function
+  named from a CPU profile, and `globe.getHeight`, `scene.sampleHeight`,
+  `scene.pick` and friends wrapped to count calls and time.
+- A long task is one main-thread task over 50 ms. With no layers on, the
+  baseline is two at load (longest about 240 ms) and none afterwards, with zero
+  frames rendered while the camera is still.
+- Four profiling sessions ran on one machine at the same time, so absolute
+  timings carry some noise. Ratios against the baseline are what to read.
+
+Nothing here was measured on Google Photorealistic 3D Tiles, on a discrete or
+integrated PC GPU, or with keyed feeds (AISStream, FIRMS, TomTom). Those rows
+are marked "read in code".
+
+## Findings and fixes
+
+Worst first. "Fix" names the pull request that carries the fix.
+
+### Measured
+
+| # | Where | What happens | Fix |
+| ---: | --- | --- | --- |
+| 1 | Bike Share, local data layers, Transit, Rail | 18 s freeze switching Bike Share on over New York (2,519 stations); 2.7 s on Data Centers; multi-second freezes with Transit while zooming | #1688, #1689 |
+| 2 | Shipwrecks | 3 to 5 s freeze when the markers are built over loaded terrain; a share link with the layer on held the loading screen for 22.9 s in one run | #1703 |
+| 3 | Camera | Rendering stops until reload: at a whole-globe view looking straight down, pan a few times, then scroll one notch | #1704 |
+| 4 | Street Traffic | Zooming at 250 m over Manhattan: 25 long tasks in 24 s, longest 746 ms, 6.6 s in total | #1705 |
+| 5 | ALPR cameras | Depth samples inside the overlay paint, repeated on every re-enable: 240 samples and about 1 s across eight toggles. A first-sample freeze of up to 1.9 s was seen in the sweep but not on a second day | #1706 |
+| 6 | Wind | First zoom after load: up to 14 long tasks (longest 414 ms). Re-measured as one-off shader links, not a standing cost: see below | none proposed |
+| 7 | Submarine cables | About 2 s of long tasks on load, heap briefly at 1 GB, about 0.5 s again on each re-enable | #1707 (first step), #1722 (batched primitives) |
+| 8 | Live Flights at whole-globe view with detection labels | Fine on the test machine; at 4x CPU throttle, 8 fps with 143 long tasks in 15 s | #1708 (fleet pass), #1719 (overlay) |
+| 9 | Radio | 7 to 10 long tasks when the directory loads, longest 447 ms | #1709 |
+| 10 | Pointer pick | Not reproduced on a second look: see below | none needed |
+| 11 | CCTV | A still-image camera holds continuous rendering at 60 frames a second although its picture changes about every 10 s | #1710 |
+
+### Read in code
+
+| # | Where | What happens | Fix |
+| ---: | --- | --- | --- |
+| 12 | `/api/firms` | The whole fire set is filtered, serialised and sent uncompressed on every request; 15 to 55 MB estimated in a heavy season | #1711 |
+| 13 | AIS store | Both vessel maps are walked on every position message, and sorted whole once past the cap | #1712 |
+| 14 | Satellite clouds on the 3D Tiles map | A CPU pass over a 4096 x 2048 image, 90 to 180 ms measured on a synthetic canvas, twice in a row | #1713 (canvas path), #1721 (shader) |
+| 15 | NVG and FLIR styles | Over 100 texture reads per pixel, and 60 renders a second while the style is on. Measured afterwards: the reads cost 0.4 ms a frame at 1440 x 900 and 1.2 ms at 2560 x 1440 | #1718 |
+| 16 | Wind server | Full 0.25 degree GRIB fields decoded on the event loop. Measured afterwards: 68 ms blocked per warm refresh, about 250 ms on the first, about 400 ms when all six keys refresh together | #1717 |
+| 17 | Imported geo files and other per-feature ground clamps | Measured afterwards: imported files do not freeze; see below | none needed |
+
+## Cause and fix, per finding
+
+### 1. Terrain height reads
+
+`globe.getHeight` casts a ray against the mesh of the tile under the point, and
+`scene.sampleHeight` renders a depth pass. Transit asked for every trail fix of
+every vehicle several times per poll; Bike Share sampled every station in one
+go. The fix keeps heights per point in one shared reader with a read budget
+(`src/services/terrainSurface.js`) and spreads the depth samples across frames.
+
+### 2. Shipwrecks
+
+`rebuild()` in `src/layers/shipwrecks/index.js` adds 7,958 billboards with
+`heightReference: CLAMP_TO_GROUND`. Each constructor runs
+`Billboard._updateClamping`, which intersects a ray with the terrain mesh,
+synchronously: 4.8 of the 4.9 s. The cost is only paid when terrain is loaded
+at the time the markers are built, so a cold start with the layer in the URL
+sometimes escapes it.
+
+Fix: do not clamp. Wrecks are at sea and the markers already ignore the depth
+test, so place them on the ellipsoid with `HeightReference.NONE`.
+
+### 3. Camera: rendering stops after pan then zoom
+
+Pure Cesium; no application code is involved. Above 1,000 km,
+`ScreenSpaceCameraController` `handleZoom` rotates the camera about the cross
+product of the picked point's normal and the screen centre's normal whenever
+their dot product is between 0 and 1. With the pointer on the exact centre pixel
+the two are the same vector, yet `n · n` often rounds to `0.9999999999999999`,
+so the check passes with a zero axis. `Camera.rotate` then throws
+`DeveloperError: normalized result is not a number` from
+`Scene.initializeFrame`, outside the scene's own try/catch, so
+`scene.renderError` never fires and Cesium stops its render loop for good. The
+pans in the first reproduction only moved the camera to a pose where the
+rounding goes that way.
+
+Fix: make `camera.rotate` ignore a zero or non-finite axis, and recover from any
+stopped loop by restoring the last drawn camera pose and restarting it a bounded
+number of times before showing Cesium's error panel.
+
+### 4. Street Traffic road loading
+
+Three costs in one task after the detail tiles arrive, in
+`src/layers/traffic/source.js`:
+
+- `outsideDetailTiles` clips every coarse z12 road against every loaded detail
+  tile (up to 16) for four regions.
+- The composed set is then handed on with `replace: true`, so
+  `ingestion.js` parses every road again although each tile was parsed as it
+  streamed.
+- `parseRoads` (`model.js`) asks `cachedGroundFloor` once per coordinate, and
+  each call builds several string keys.
+
+Fix: clip once per coarse tile against the detail tiles' union box and slice the
+work across frames (or do it in the vector-tile worker); reuse the roads parsed
+while streaming and parse only the clipped coarse remainder; look the floor up
+once per floor cell within a parse.
+
+This is separate from the one-viewport-tile-at-a-time loading recorded in
+[KNOWN-ISSUES.md](KNOWN-ISSUES.md).
+
+### 5. ALPR cameras
+
+`refineAnchors` and `anchorFor` in `src/layers/alpr/overlay.js` call
+`scene.sampleHeight` from the overlay's paint, four per paint. Each is a depth
+render and a `readPixels`; the first one also compiles the pick shader. Results
+are kept on the entity, so a rebuild or a re-enable samples everything again.
+
+Fix: on a terrain globe read `globe.getHeight` through the shared terrain reader
+instead of sampling; keep the answers in a map keyed by camera that outlives the
+entities; move what sampling remains out of the paint into a queue of one per
+frame.
+
+### 6. Wind
+
+The first reading blamed the layer's 916,476 vertices for slow depth reads
+during zoom. Measuring again did not support that: depth reads cost the same
+with and without Wind, hiding every wind primitive left pick time unchanged, and
+the stalls appear on the first zoom only, as shader programs link (seven
+programs, about 0.5 s, long tasks up to 166 ms). Later zooms had none.
+
+The roughly 30 renders a second are the animation itself. It is already capped
+at 30 Hz and stops when paused, hidden, out of view or under reduced motion;
+lowering the rate would change how the layer looks. `disable()` releases the
+baked geometry on purpose, at the price of one task of about 130 ms on
+re-enable.
+
+A third look, timing every program link on a preview build, settled it: Wind
+owns two shader programs, both link during load in 9 to 18 ms, and none ever
+linked during a zoom. The programs that do link on a zoom are Cesium's own
+globe-surface variants, with Wind on or off, and Cesium links them
+synchronously. No fix is proposed.
+
+### 7. Submarine cables
+
+`src/layers/submarineCables/ingestion.js` loads both collections through
+`Cesium.GeoJsonDataSource` with `clampToGround`. Switching the layer on is one
+task of about 1.4 s, and 1.2 s of it is Cesium reading the terrain height for
+the 1,917 ground-clamped landing markers, all created in the first frame,
+including the ones behind the globe.
+
+Fix, first step: start the landing markers hidden and let the existing horizon
+sweep show the visible ones a few dozen per frame.
+
+Fix, second step: draw from batched primitives in place of the entity data
+sources: one ground polyline primitive for the lines, one billboard collection
+for the landing markers, one point collection and one static polyline primitive
+for the reference stems, all kept while the layer is off. That removes the
+visualiser tasks, the stall on switch-off and on re-enable, and about 900 MB of
+heap. The first switch-on still links shaders and builds the ground-line
+geometry once.
+
+### 8. Live Flights at whole-globe view
+
+Two costs that scale with the 7,500 aircraft of a full poll:
+
+- The fleet pass (`src/layers/flights/rendering.js`, every 80 ms) dead-reckons
+  each visible aircraft and asks `cachedGroundFloor` for it, including aircraft
+  at cruise altitude that can never touch the floor. Each lookup formats numbers
+  to strings several times and rewrites a cache entry: 40% of the busy time.
+- The detection overlay (`src/data/detection.js` `_drawOverlay`) collects every
+  detectable object and strokes every bracket on every frame.
+
+Fix for the first: skip the floor path for a contact clearly above any terrain,
+make the floor-cell key a number, and stop promoting the cache entry on every
+read.
+
+The second turned out smaller than it looked. The bracket strokes are already
+one path per colour, and collecting the objects is about 3 ms of a 56 ms frame
+at 4x throttle once the first fix is in. What costs is the per-object loop in
+`_drawOverlay` (projection, occlusion, alpha, twelve path calls per bracket).
+
+Fix for the second: keep what a sweep built and reuse it on the next paint when
+the view and every contact are exactly what it was built from, compared value
+by value so no layer has to announce a change. Between two fleet passes most
+paints qualify, which cuts frame work by a fifth to a third on a still camera
+at full speed. At 4x throttle a frame outlasts a fleet pass, no paint
+qualifies, and the gain is a few milliseconds; the fleet pass is what
+dominates there.
+
+### 9. Radio
+
+`stationTags()` in `src/layers/radio/categories.js` splits and normalises a
+station's tags on every `hasTag` call, and `buildRadioCategories` runs that for
+every station against every category, twice.
+
+Fix: normalise once per station at ingest and count categories from that.
+
+### 10. Pointer pick
+
+Three sessions saw a single `scene.pick` of 207 to 342 ms during a gesture and
+attributed it to `pickPointer` in `src/voice/pointerPick.js`. Timing every pick
+across pointer rests, drags and wheel bursts did not bear that out: of 78 picks
+with CCTV on over London all but two took 3 to 8 ms, and with five heavy layers
+on, 81 picks took 5 to 30 ms apart from the first (135 ms). `pickPointer` picks
+at most once per pointer rest.
+
+The slow pick is the first pick after a layer appears, once per page load, most
+likely the pick shader compiling, and its stack is CCTV's own hover pick
+(`src/layers/cctv/hover.js`). No fix is proposed: removing the dwell pick would
+only move the one-off cost to the next click.
+
+### 11. CCTV still-image cameras
+
+`src/layers/cctv/projection.js` holds continuous rendering for as long as any
+projected camera is active and redraws the projection every frame.
+
+Fix: hold only for video. For a still image, request one render when a new image
+lands or while a focus fade runs.
+
+### 12. `/api/firms`
+
+`server/providers/firms.js` builds the payload and calls `JSON.stringify` per
+request, with no kept body and no compression, and the client refetches every
+ten minutes.
+
+Fix: keep the response bytes and their gzip and serve those, as the OpenSky
+provider does. The route filters to the trailing 24 hours at serve time, so the
+bytes can only be reused while that filter keeps the same records (about a
+minute at a time): bursts and several clients gain most, and every response is
+about seven times smaller.
+
+### 13. AIS store
+
+`server/providers/vessels/ais-store.js` calls `pruneAisStreamCache()` for every
+message; the static-data map is never pruned.
+
+Fix: prune on a timer, evict in insertion order, and drop a vessel's static
+entry with the vessel.
+
+### 14. Satellite clouds on the 3D Tiles map
+
+`src/layers/weather/infraredImage.js` runs `getImageData`, a per-pixel power
+curve and `putImageData` over the whole canvas.
+
+Fix: a 256-entry lookup table applied in place for the canvas path, which
+halves it; then, for the shell on the 3D Tiles map, the same curve in its
+fragment shader from a strength uniform, so the image is never read back and a
+strength change builds no new image.
+
+### 15. NVG and FLIR styles
+
+`src/styles/surveillance.js` loops 11 x 11 texture reads per pixel and
+`src/styles/thermal.js` totals 106. Timed on the GPU, those loops cost about
+0.4 ms a frame at 1440 x 900 and 1.2 ms at 2560 x 1440 on the test machine:
+real, but small there. The standing cost is that a style with animated grain
+holds continuous rendering at 60 frames a second.
+
+Fix: split the bloom into a row pass and a column pass, which gives the same
+picture from a fifth to a half of the reads, and step the grain's clock at
+15 Hz, asking for one frame per step instead of holding the render loop. The
+grain then changes 15 times a second, which is visible in motion.
+
+Switching on any style stage at all costs more than the bloom did (1.8 ms a
+frame at 1440 x 900 for the one-line noir style). That was not looked into.
+
+### 16. Wind server
+
+`server/providers/wind/decode.js` decodes about a million doubles per message
+synchronously, hourly, for six keys.
+
+Fix: decode on a worker thread, and keep the sampled U and V of the last
+forecast file per model so that choosing an overlay fetches only its field.
+
+### 17. Per-feature ground clamps
+
+`heightReference: CLAMP_TO_GROUND` per feature is also set in
+`installations/rendering.js`, `alpr/presentation.js`, `ghostMaps/index.js`,
+`earthquakes/index.js`, `airQuality/index.js`, `news/index.js` and
+`osmPlaces/index.js`. Their counts were small in these runs (30 to 1,500) and
+none froze.
+
+Imported geo files were the one unbounded case, and measuring them cleared
+them: 20,000 generated points (the import cap) finish in about 1.5 s with a
+longest task near 0.5 s, because `settleGroundPins` in
+`src/data/geoFileImport.js` already places pins with `HeightReference.NONE` and
+resolves heights 256 at a time with a yield between batches. No fix is needed.
+
+## Checked and fine
+
+- Start-up of a production build: viewer ready in about 0.5 s, loading screen
+  gone at 1.6 s, three long tasks totalling about 300 ms.
+- Idle: no frames rendered with no layers on; every render hold was released
+  when its layer went off.
+- Leaks: all 41 layers toggled three times and ten of them eight times; no
+  timer, scene listener, primitive or data source grew per cycle. The heap
+  levelled off near 320 MB over 7.5 minutes of toggling eleven layers.
+- At most one long task after load: Military, Satellites (including 11,903
+  Starlink points), Earthquakes, News, Wildlife, GNSS, Drone Airspace, Military
+  Installations, Fire Perimeters, rain radar, lightning, and satellite clouds on
+  the globe map.
+- Live Flights at city scale with the same 7,500 aircraft loaded: 60 fps, no
+  long tasks.
+
+## Not covered
+
+- Google Photorealistic 3D Tiles: nothing was run there. Depth sampling is the
+  only height source on that map, so findings 4, 5 and 17 may be worse.
+- Live Vessels, FIRMS with data, TomTom traffic, Local ADS-B.
+- Frame rate on anything but one Apple silicon machine.
+- One all-layers run over Manhattan grew the heap from 346 to 638 MB in 60 s;
+  whether that is retained was not established.
+- One Satellites load showed a 5.2 s long task once and never again in four more
+  loads.

docs/PERFORMANCE.md

@@ -6,6 +6,9 @@ specification and should not be used to predict performance on untested systems.
 The original capture artifacts are not included here, so this page records
 results rather than defining a runnable benchmark.
 
+For slowdowns found since, with their causes and fixes, see
+[PERFORMANCE-AUDIT-2026-11.md](PERFORMANCE-AUDIT-2026-11.md).
+
 ## Test context
 
 The baseline was captured on 22 August 2026 with these conditions:

src/layers/traffic/flow.js

@@ -1,7 +1,6 @@
 import { roadIdentity } from './retention.js';
 import * as Cesium from 'cesium';
 import {
-  floorCellReader,
   prepareRoadSurfaces,
   roadHeightStations,
   trafficSurfaceReady,
@@ -302,7 +301,6 @@ export function createFlow({ state: layerState, services, parts, source }) {
       }
     }
     if (depthHeight !== undefined) layerState._viewHeightEstimate = depthHeight;
-    const floorAt = floorCellReader(services.ground);
     for (const road of roads) {
       road.key ||= roadIdentity(road);
       const prepared = !refining && preparedRoads.get(road.key);
@@ -321,7 +319,7 @@ export function createFlow({ state: layerState, services, parts, source }) {
         );
         for (let i = 0; i < road.coords.length; i++) {
           const [lon, lat] = road.coords[i];
-          const floor = floorAt(lat, lon);
+          const floor = services.ground?.cachedGroundFloor?.(lat, lon);
           const height =
             Number.isFinite(floor) && Math.abs(floor) <= 9000
               ? Math.max(floor, layerState._viewHeightEstimate)

src/layers/traffic/index.js

@@ -39,10 +39,10 @@ export function createTrafficLayer({ services, source }) {
   parts.controls = createControls(context);
   parts.lifecycle = createLifecycle(context);
   state._parseRoads = TRAFFIC_TIMING_ENABLED
-    ? (data, trace, parsedBySource) =>
+    ? (data, trace) =>
         trace
-          ? parts.timing.parseRoadsTimed(data, trace, parsedBySource)
-          : parts.model.parseRoads(data, trace, parsedBySource)
+          ? parts.timing.parseRoadsTimed(data, trace)
+          : parts.model.parseRoads(data)
     : parts.model.parseRoads;
 
   state._loadRoadsForBounds = TRAFFIC_TIMING_ENABLED

src/layers/traffic/ingestion.js

@@ -348,16 +348,11 @@ export function createIngestion({
     layerState._retainedPreview = false;
     layerState._detailRoadsReady = false;
     let paintRevision = 0;
-    // The snapshot that ends a pass replaces the streamed roads with the
-    // composed set, which is mostly the tile records already parsed and
-    // drawn. Remembering those per pass means only the records new to that
-    // snapshot (the clipped coarse roads) are parsed, not the whole set again.
-    let parsedBySource = new WeakMap();
     const onTile = (data, passSignal, preview) => {
       if (generation !== layerState._loadGeneration || passSignal.aborted)
         return;
       const start = performance.now();
-      const parsed = layerState._parseRoads(data, trace, parsedBySource);
+      const parsed = layerState._parseRoads(data, trace);
       phaseTiming('parse', start, { roads: parsed.length, incremental: true });
       if (data.replace) streamed = parsed;
       else streamed.push(...parsed);
@@ -536,7 +531,6 @@ export function createIngestion({
       if (altitude > FAST_FETCH_ALTITUDE) return;
 
       streamed = [];
-      parsedBySource = new WeakMap();
       majorPass = false;
       // Detailed pass: fetch the full road graph (tertiary, residential, etc.)
       console.log(`[Data:Traffic] Full fetch local roads [${cacheKey}]`);

src/layers/traffic/model.js

@@ -1,5 +1,5 @@
 import * as Cesium from 'cesium';
-import { floorCellReader, roadSurfaceChunks } from './surface.js';
+import { roadSurfaceChunks } from './surface.js';
 import { t, translateKnown } from '../../i18n/index.js';
 import {
   flowDensityMult,
@@ -13,35 +13,22 @@ import {
 } from './policy.js';
 
 export function createModel({ state: layerState, services, parts, source }) {
-  /**
-   * Build scene waypoints from source records; thinning and terrain remain rendering policy.
-   *
-   * `parsedBySource` (source record → its parsed roads) is filled as records
-   * are parsed, and a record already in it is answered from it.
-   */
-  function parseRoads(roadData, _trace, parsedBySource) {
+  /** Build scene waypoints from source records; thinning and terrain remain rendering policy. */
+  function parseRoads(roadData) {
     if (!roadData || !roadData.roads) {
       return [];
     }
 
     const roads = [];
-    const floorAt = floorCellReader(services.ground);
     for (const road of roadData.roads) {
       if (!road.coordinates || road.coordinates.length < 2) continue;
-      // A replacing snapshot repeats records this load already parsed.
-      const known = parsedBySource?.get(road);
-      if (known) {
-        for (const parsed of known) roads.push(parsed);
-        continue;
-      }
-      const first = roads.length;
 
       for (const coords of roadSurfaceChunks(road.coordinates)) {
         const type = road.type;
         const oneway = road.oneway;
         // Pre-compute Cartesian3 waypoints (lon, lat, height) for fast lerp animation
         const waypoints = coords.map(([lng, lat]) => {
-          const floor = floorAt(lat, lng);
+          const floor = services.ground?.cachedGroundFloor?.(lat, lng);
           const h =
             (Number.isFinite(floor) && Math.abs(floor) <= 9000
               ? floor
@@ -73,7 +60,6 @@ export function createModel({ state: layerState, services, parts, source }) {
             flow: road.flow || null,
           });
       }
-      parsedBySource?.set(road, roads.slice(first));
     }
 
     return roads;

src/layers/traffic/roadLoadCost.test.mjs

@@ -1,444 +0,0 @@
-import test from 'node:test';
-import assert from 'node:assert/strict';
-import * as Cesium from 'cesium';
-import { createTrafficSource, outsideDetailTiles } from './source.js';
-import { createIngestion } from './ingestion.js';
-import { createModel } from './model.js';
-import { floorCellReader, roadSurfaceChunks } from './surface.js';
-import { DOT_HEIGHT_OFFSET } from './policy.js';
-import { clipTileLine } from '../../sources/openFreeMap.js';
-import { tileToBBox } from '../../data/tomtomTiles.js';
-
-// The clip as it was before the extent shortcut: every road against the four
-// regions around every tile. The shortcut must return exactly this.
-function clipEveryRoadAgainstEveryTile(roads, tiles) {
-  return roads.flatMap((road) => {
-    let lines = [road.coordinates];
-    for (const tile of tiles) {
-      const box = tileToBBox(tile.z, tile.x, tile.y);
-      const regions = [
-        { west: -180, east: box.west, south: -85, north: 85 },
-        { west: box.east, east: 180, south: -85, north: 85 },
-        { west: box.west, east: box.east, south: -85, north: box.south },
-        { west: box.west, east: box.east, south: box.north, north: 85 },
-      ];
-      lines = lines.flatMap((line) =>
-        regions.flatMap((region) => clipTileLine(line, region)),
-      );
-    }
-    return lines.map((coordinates) => ({ ...road, coordinates }));
-  });
-}
-
-function seeded(seed) {
-  let state = seed >>> 0;
-  return () => {
-    state = (Math.imul(state, 1664525) + 1013904223) >>> 0;
-    return state / 2 ** 32;
-  };
-}
-
-function tileBlock(x, y, size = 4) {
-  const tiles = [];
-  for (let dx = 0; dx < size; dx++)
-    for (let dy = 0; dy < size; dy++)
-      tiles.push({ z: 14, x: x + dx, y: y + dy });
-  return tiles;
-}
-
-/** Roads in and around a tile block: wandering, straight, tiny, and on tile edges. */
-function roadsAround(tiles, random, count = 400) {
-  const boxes = tiles.map((tile) => tileToBBox(tile.z, tile.x, tile.y));
-  const west = Math.min(...boxes.map((box) => box.west)),
-    east = Math.max(...boxes.map((box) => box.east)),
-    south = Math.min(...boxes.map((box) => box.south)),
-    north = Math.max(...boxes.map((box) => box.north));
-  const width = east - west,
-    height = north - south;
-  const roads = [];
-  for (let i = 0; i < count; i++) {
-    const step = i % 7 === 0 ? 0.00002 : i % 3 === 0 ? 0.01 : 0.002;
-    let lon = west - width / 2 + random() * width * 2,
-      lat = south - height / 2 + random() * height * 2;
-    const coordinates = [[lon, lat]];
-    const points = 1 + Math.floor(random() * 12);
-    for (let j = 0; j < points; j++) {
-      lon += (random() - 0.5) * step;
-      lat += (random() - 0.5) * step;
-      coordinates.push([lon, lat]);
-    }
-    roads.push({ type: 'primary', oneway: i % 2, id: i, coordinates });
-  }
-  const box = boxes[5];
-  const midLat = (box.south + box.north) / 2,
-    midLon = (box.west + box.east) / 2;
-  roads.push(
-    // Along a tile edge, ending on a corner, and touching an edge from outside.
-    {
-      id: 'edge',
-      coordinates: [
-        [box.west, box.south - 0.01],
-        [box.west, box.north + 0.01],
-      ],
-    },
-    {
-      id: 'corner',
-      coordinates: [
-        [box.west - 0.01, box.south - 0.01],
-        [box.west, box.south],
-        [box.east, box.north],
-      ],
-    },
-    {
-      id: 'touch',
-      coordinates: [
-        [box.west - 0.01, midLat],
-        [box.west, midLat],
-      ],
-    },
-    // Across the whole block, and a repeated vertex.
-    {
-      id: 'across',
-      coordinates: [
-        [west - 0.01, midLat],
-        [east + 0.01, midLat + 0.0003],
-      ],
-    },
-    {
-      id: 'repeat',
-      coordinates: [
-        [midLon, midLat],
-        [midLon, midLat],
-        [midLon + 0.001, midLat],
-      ],
-    },
-    // Records the clip drops or leaves alone.
-    { id: 'single', coordinates: [[west - 0.02, midLat]] },
-    { id: 'empty', coordinates: [] },
-    {
-      id: 'negative-zero',
-      coordinates: [
-        [-0, south - 0.02],
-        [0.001, south - 0.02],
-      ],
-    },
-    {
-      id: 'polar',
-      coordinates: [
-        [west - 0.02, 86],
-        [west - 0.02, 86.01],
-      ],
-    },
-  );
-  return roads;
-}
-
-for (const [place, x, y] of [
-  ['Manhattan', 4823, 6158],
-  ['London, across longitude 0', 8190, 5446],
-  ['longitude 0 and latitude 0', 8190, 8190],
-  ['the southern and eastern hemispheres', 15070, 9826],
-])
-  test(`coarse roads clipped around detail tiles match the every-tile clip: ${place}`, () => {
-    const tiles = tileBlock(x, y);
-    const roads = roadsAround(tiles, seeded(x * 31 + y));
-    for (const loaded of [tiles, tiles.slice(0, 5), tiles.slice(3, 4), []]) {
-      const expected = clipEveryRoadAgainstEveryTile(roads, loaded);
-      assert.ok(loaded.length === 0 || expected.length !== roads.length);
-      // deepStrictEqual separates -0 from 0 and compares every vertex exactly.
-      assert.deepStrictEqual(outsideDetailTiles(roads, loaded), expected);
-    }
-  });
-
-test('only a road that reaches a detail tile is clipped against it', () => {
-  const tiles = tileBlock(4823, 6158);
-  const block = tiles.map((tile) => tileToBBox(tile.z, tile.x, tile.y));
-  const west = Math.min(...block.map((box) => box.west)),
-    north = Math.max(...block.map((box) => box.north));
-  // 300 roads beside the block and between its tile edges, none touching one.
-  const clear = [];
-  for (let i = 0; i < 300; i++) {
-    const box = block[i % block.length];
-    const lon = i % 2 ? west - 0.02 - i * 1e-5 : box.west + 0.004;
-    const lat = i % 2 ? box.south + 0.004 : north + 0.01 + i * 1e-5;
-    clear.push({
-      coordinates: [
-        [lon, lat],
-        [lon + 0.002, lat + 0.0005],
-        [lon + 0.003, lat + 0.001],
-      ],
-    });
-  }
-  const first = block[0];
-  const crossing = {
-    coordinates: [
-      [first.west + 0.004, north + 0.01],
-      [first.west + 0.004, (first.south + first.north) / 2],
-    ],
-  };
-  let clips = 0;
-  const counted = (line, region) => {
-    clips++;
-    return clipTileLine(line, region);
-  };
-  const roads = outsideDetailTiles([...clear, crossing], tiles, counted);
-  assert.deepStrictEqual(
-    roads,
-    clipEveryRoadAgainstEveryTile([...clear, crossing], tiles),
-  );
-  assert.equal(roads.length, 301);
-  // Four regions for each tile the crossing road reaches, never the 19,264
-  // clips of every road against every tile.
-  assert.ok(clips >= 4, `expected the crossing road to be clipped: ${clips}`);
-  assert.ok(clips <= 4 * tiles.length, `clipped ${clips} times`);
-});
-
-/** A DEM-regime ground service: one floor per toFixed(3) cell, counting reads. */
-function cellGround({ mesh = false, warm = () => true } = {}) {
-  const ground = {
-    reads: 0,
-    meshFloorPreferred: () => mesh,
-    cachedGroundFloor(lat, lon) {
-      ground.reads++;
-      if (!Number.isFinite(lat) || !Number.isFinite(lon)) return null;
-      // Number() as the shared cache does it: "-0.000" and "0.000" are one cell.
-      const cell = `${Number(lat.toFixed(3))},${Number(lon.toFixed(3))}`;
-      if (!warm(cell)) return null;
-      let hash = 0;
-      for (const character of cell)
-        hash = (Math.imul(hash, 31) + character.charCodeAt(0)) | 0;
-      // The mesh regime answers per point, not per cell.
-      return (hash % 4000) / 10 + (mesh ? lat - Math.floor(lat * 1000) / 1000 : 0);
-    },
-  };
-  return ground;
-}
-
-test('floor reads are shared per cell and equal the per-coordinate reads', () => {
-  const random = seeded(7);
-  const points = [];
-  for (let i = 0; i < 4000; i++)
-    points.push([40.75 + random() * 0.01, -73.99 + random() * 0.01]);
-  // Cell edges, where toFixed(3) and Math.round can disagree, in each sign.
-  for (const lat of [40.7505, -40.7505, 0.0005, -0.0005, 1.0005, 8.5745])
-    for (const lon of [-73.9905, 73.9905, 0.0005, -0.0005, 1.0005, 2.3515])
-      points.push([lat, lon], [lat + 1e-9, lon - 1e-9], [lat - 1e-9, lon]);
-  points.push([Number.NaN, 0], [0, Infinity], [0, 0], [-0, -0]);
-
-  const direct = cellGround();
-  const expected = points.map(([lat, lon]) =>
-    direct.cachedGroundFloor(lat, lon),
-  );
-  const ground = cellGround();
-  const floorAt = floorCellReader(ground);
-  assert.deepStrictEqual(
-    points.map(([lat, lon]) => floorAt(lat, lon)),
-    expected,
-  );
-  // 4000 points in a 0.01 degree square share about 121 cells.
-  assert.ok(ground.reads < 600, `read the shared cache ${ground.reads} times`);
-
-  // A cold cell is remembered as cold for the pass, not asked again.
-  const cold = cellGround({ warm: () => false });
-  const coldAt = floorCellReader(cold);
-  assert.equal(coldAt(40.7512, -73.9812), null);
-  assert.equal(coldAt(40.7513, -73.9813), null);
-  assert.equal(cold.reads, 1);
-});
-
-test('mesh floors and unknown ground services are read per coordinate', () => {
-  const mesh = cellGround({ mesh: true });
-  const meshAt = floorCellReader(mesh);
-  const a = meshAt(40.7512, -73.9812),
-    b = meshAt(40.75121, -73.9812);
-  assert.equal(mesh.reads, 2);
-  assert.notEqual(a, b);
-
-  // No regime to ask: nothing says a floor is the same across a cell.
-  let reads = 0;
-  const bareAt = floorCellReader({ cachedGroundFloor: () => ++reads });
-  bareAt(40.7512, -73.9812);
-  bareAt(40.7512, -73.9812);
-  assert.equal(reads, 2);
-  assert.equal(floorCellReader(undefined)(1, 2), undefined);
-  assert.equal(floorCellReader({})(1, 2), undefined);
-});
-
-function road(lon, lat, points = 40) {
-  const coordinates = [];
-  for (let i = 0; i < points; i++)
-    coordinates.push([lon + i * 0.00004, lat + i * 0.00003]);
-  return { type: 'residential', oneway: 1, coordinates };
-}
-
-test('parsing reads each floor cell once and builds the same waypoints', () => {
-  const ground = cellGround({ warm: (cell) => !cell.endsWith('3') });
-  const state = { _viewHeightEstimate: 12 };
-  const model = createModel({
-    state,
-    services: { ground },
-    parts: {},
-    source: {},
-  });
-  const records = [road(-73.99, 40.75), road(-73.9899, 40.7501)];
-  const parsed = model.parseRoads({ roads: records });
-  const coordinates = records.reduce(
-    (count, record) => count + record.coordinates.length,
-    0,
-  );
-  assert.ok(
-    ground.reads < coordinates / 3,
-    `${ground.reads} floor reads for ${coordinates} coordinates`,
-  );
-
-  const direct = cellGround({ warm: (cell) => !cell.endsWith('3') });
-  const expected = records.flatMap((record) =>
-    roadSurfaceChunks(record.coordinates).map((coords) =>
-      coords.map(([lon, lat]) => {
-        const floor = direct.cachedGroundFloor(lat, lon);
-        return Cesium.Cartesian3.fromDegrees(
-          lon,
-          lat,
-          (floor ?? state._viewHeightEstimate) + DOT_HEIGHT_OFFSET,
-        );
-      }),
-    ),
-  );
-  assert.ok(direct.reads >= coordinates);
-  assert.deepStrictEqual(
-    parsed.map((entry) => entry.waypoints),
-    expected,
-  );
-});
-
-test('a record parsed earlier in the pass is not parsed again', () => {
-  const ground = cellGround();
-  const model = createModel({
-    state: {},
-    services: { ground },
-    parts: {},
-    source: {},
-  });
-  const first = { ...road(-73.99, 40.75), oneway: 0 },
-    second = road(-73.98, 40.76),
-    short = { type: 'primary', coordinates: [[-73.97, 40.77]] };
-  const parsedBySource = new WeakMap();
-  const tile = model.parseRoads({ roads: [first] }, null, parsedBySource);
-  assert.equal(tile.length, 2, 'a two-way record parses to both directions');
-  const reads = ground.reads;
-  const replaced = model.parseRoads(
-    { roads: [second, short, first], replace: true },
-    null,
-    parsedBySource,
-  );
-  assert.equal(replaced.length, 3);
-  // The same parsed roads, in the snapshot's order: dots stay attached.
-  assert.equal(replaced[1], tile[0]);
-  assert.equal(replaced[2], tile[1]);
-  const fresh = cellGround();
-  createModel({
-    state: {},
-    services: { ground: fresh },
-    parts: {},
-    source: {},
-  }).parseRoads({ roads: [second] });
-  assert.equal(ground.reads - reads, fresh.reads, 'only the new record read');
-
-  // Without the map every call parses, as before.
-  const again = model.parseRoads({ roads: [first] });
-  assert.notEqual(again[0], tile[0]);
-  assert.deepStrictEqual(again, tile);
-});
-
-test('the snapshot that ends a pass parses only the records it adds', async () => {
-  const detail = { z: 14, x: 3743, y: 6745 };
-  const core = tileToBBox(detail.z, detail.x, detail.y);
-  const local = {
-    type: 'residential',
-    oneway: 1,
-    coordinates: [
-      [core.west + 0.002, core.south + 0.002],
-      [core.west + 0.004, core.south + 0.004],
-    ],
-  };
-  const distant = {
-    type: 'primary',
-    oneway: 1,
-    coordinates: [
-      [core.east + 0.01, core.south],
-      [core.east + 0.02, core.south],
-    ],
-  };
-  const bounds = {
-    ...core,
-    east: core.east + 0.03,
-    coverage: {
-      detail: [detail],
-      coarse: [{ z: 12, x: 935, y: 1686 }],
-      key: 'test',
-    },
-  };
-  const source = createTrafficSource({
-    mapTiles: {
-      async fetchBounds(box, { zoom, onTile }) {
-        const tile = { roads: zoom === 14 ? [local] : [distant] };
-        onTile?.(tile);
-        return {
-          tiles: [tile],
-          loadedTiles: zoom === 14 ? [detail] : bounds.coverage.coarse,
-          partial: false,
-        };
-      },
-    },
-  });
-  const parsedRecords = [];
-  const painted = [];
-  const state = {
-    _enabled: true,
-    _loadGeneration: 0,
-    _tileCache: new Map(),
-    _roadMode: null,
-    _liveMode: false,
-    // The model's contract: fill the map, answer known records from it.
-    _parseRoads: (data, trace, parsedBySource) =>
-      data.roads.flatMap((record) => {
-        const known = parsedBySource?.get(record);
-        if (known) return known;
-        parsedRecords.push(record);
-        const parsed = [{ record }];
-        parsedBySource?.set(record, parsed);
-        return parsed;
-      }),
-  };
-  const ingestion = createIngestion({
-    state,
-    source,
-    services: {},
-    parts: {
-      viewport: {
-        clampBounds: (b) => b,
-        getBoundsCenter: () => ({ lat: 30.26, lon: -97.74 }),
-      },
-      flow: {
-        warmFlow: () => Promise.resolve([]),
-        applyFlowThenRender: async (roads, box, generation, altitude, label) => {
-          if (label === 'Loaded full') painted.push(roads);
-          return true;
-        },
-      },
-    },
-  });
-  await ingestion.loadRoadsForBounds(bounds, 350);
-  assert.equal(
-    parsedRecords.filter((record) => record === local).length,
-    1,
-    'the detail tile record is parsed when its tile streams, not again',
-  );
-  // The full graph is still the detail record plus the coarse road outside it.
-  assert.equal(painted.at(-1).length, 2);
-  assert.equal(painted.at(-1)[0].record, local);
-  assert.deepStrictEqual(
-    painted.at(-1)[1].record.coordinates,
-    distant.coordinates,
-  );
-});

src/layers/traffic/source.js

@@ -33,108 +33,23 @@ export function trafficDetailBounds(box) {
   return detail;
 }
 
-/** Longitude/latitude extent of one line; NaN coordinates leave it unusable. */
-function lineExtent(coordinates) {
-  let west = Infinity,
-    east = -Infinity,
-    south = Infinity,
-    north = -Infinity;
-  for (const [lon, lat] of coordinates) {
-    if (!(lon >= west)) west = lon;
-    if (!(lon <= east)) east = lon;
-    if (!(lat >= south)) south = lat;
-    if (!(lat <= north)) north = lat;
-  }
-  return { coordinates, west, east, south, north, settled: false };
-}
-
-/**
- * What `clipTileLine` returns for a line lying wholly inside the clip region:
- * the same line with each vertex recomputed from the one before it. Returns
- * null for a line under the 12 m floor `clipTileLine` drops.
- */
-function unclippedLine(coordinates) {
-  if (coordinates.length < 2) return null;
-  const out = [];
-  let metres = 0;
-  for (let i = 1; i < coordinates.length; i++) {
-    const a = coordinates[i - 1],
-      b = coordinates[i];
-    const dx = b[0] - a[0],
-      dy = b[1] - a[1];
-    if (i === 1) out.push([a[0] + 0 * dx, a[1] + 0 * dy]);
-    out.push([a[0] + dx, a[1] + dy]);
-    metres +=
-      Math.hypot(
-        (out[i][0] - out[i - 1][0]) * Math.cos((out[i][1] * Math.PI) / 180),
-        out[i][1] - out[i - 1][1],
-      ) * 111320;
-  }
-  return metres >= 12 ? out : null;
-}
-
-const sameLine = (a, b) =>
-  a.every(
-    (point, i) => Object.is(point[0], b[i][0]) && Object.is(point[1], b[i][1]),
-  );
-
-/**
- * Keep coarse roads only outside the detailed tile cores.
- *
- * Each tile splits a line into the four regions around its core. Nearly every
- * coarse road lies wholly inside one of those regions for nearly every tile,
- * where the clip hands the line back unchanged, so that case is answered from
- * the line's extent and only a line that reaches a tile's core or edge is
- * clipped. Clipping every road against every tile froze the page for hundreds
- * of milliseconds per road load at street level.
- *
- * `clip` is injectable for tests.
- */
-export function outsideDetailTiles(roads, tiles, clip = clipTileLine) {
-  const boxes = tiles.map((tile) => tileToBBox(tile.z, tile.x, tile.y));
+/** Keep coarse roads only outside the detailed tile cores. */
+export function outsideDetailTiles(roads, tiles) {
   return roads.flatMap((road) => {
-    let lines = [lineExtent(road.coordinates)];
-    for (const box of boxes) {
-      const next = [];
-      for (const line of lines) {
-        // Strictly inside one region, and inside the bounds every region
-        // shares: the other three regions return nothing.
-        const clear =
-          line.west > -180 &&
-          line.east < 180 &&
-          line.south > -85 &&
-          line.north < 85 &&
-          (line.east < box.west ||
-            line.west > box.east ||
-            (line.west > box.west &&
-              line.east < box.east &&
-              (line.north < box.south || line.south > box.north)));
-        if (!clear) {
-          const regions = [
-            { west: -180, east: box.west, south: -85, north: 85 },
-            { west: box.east, east: 180, south: -85, north: 85 },
-            { west: box.west, east: box.east, south: -85, north: box.south },
-            { west: box.west, east: box.east, south: box.north, north: 85 },
-          ];
-          for (const region of regions)
-            for (const coordinates of clip(line.coordinates, region))
-              next.push(lineExtent(coordinates));
-        } else if (line.settled) {
-          next.push(line);
-        } else {
-          // The first unclipped pass can still move a vertex by a rounding
-          // step (a road crossing longitude or latitude 0); once a pass
-          // changes nothing, no later one will.
-          const coordinates = unclippedLine(line.coordinates);
-          if (!coordinates) continue;
-          const kept = lineExtent(coordinates);
-          kept.settled = sameLine(coordinates, line.coordinates);
-          next.push(kept);
-        }
-      }
-      lines = next;
+    let lines = [road.coordinates];
+    for (const tile of tiles) {
+      const box = tileToBBox(tile.z, tile.x, tile.y);
+      const regions = [
+        { west: -180, east: box.west, south: -85, north: 85 },
+        { west: box.east, east: 180, south: -85, north: 85 },
+        { west: box.west, east: box.east, south: -85, north: box.south },
+        { west: box.west, east: box.east, south: box.north, north: 85 },
+      ];
+      lines = lines.flatMap((line) =>
+        regions.flatMap((region) => clipTileLine(line, region)),
+      );
     }
-    return lines.map(({ coordinates }) => ({ ...road, coordinates }));
+    return lines.map((coordinates) => ({ ...road, coordinates }));
   });
 }
 

src/layers/traffic/surface.js

@@ -69,45 +69,6 @@ export function trafficSurfaceReady(scene) {
   return currentRenderedFrame(scene)?.ready === true;
 }
 
-/**
- * Ground-floor reads for one synchronous pass over road coordinates, asking
- * the shared cache once per floor cell instead of once per coordinate.
- *
- * A road tile puts thousands of coordinates into a few hundred ~111 m cells,
- * and each shared read formats and looks up two string keys, which added up
- * to seconds per street-level load. Mesh floors answer per point (the nearest
- * reading in the cell), so they are read through unchanged; only the DEM
- * regime is one value per cell. Build a reader per pass: cells warm up
- * between passes.
- */
-export function floorCellReader(ground) {
-  const read = ground?.cachedGroundFloor;
-  if (!read) return () => undefined;
-  if (ground.meshFloorPreferred?.() !== false)
-    return (lat, lon) => read(lat, lon);
-  const cells = new Map();
-  return (lat, lon) => {
-    const y = lat * 1000,
-      x = lon * 1000;
-    const row = Math.round(y),
-      column = Math.round(x);
-    // The shared cache rounds with toFixed(3). At a cell edge that and
-    // Math.round can pick different cells, so an edge point asks directly.
-    if (!(
-      Math.abs(Math.abs(y - row) - 0.5) > 1e-6 &&
-      Math.abs(Math.abs(x - column) - 0.5) > 1e-6
-    ))
-      return read(lat, lon);
-    const key = row * 1e6 + column;
-    let floor = cells.get(key);
-    if (floor === undefined) {
-      floor = read(lat, lon) ?? null;
-      cells.set(key, floor);
-    }
-    return floor;
-  };
-}
-
 /** Preserve bends and insert height samples at most 150 m apart, splitting long roads. */
 export function roadSurfaceChunks(coordinates) {
   const chunks = [];

src/layers/traffic/timing.js

@@ -1,5 +1,5 @@
 import * as Cesium from 'cesium';
-import { floorCellReader, roadSurfaceChunks } from './surface.js';
+import { roadSurfaceChunks } from './surface.js';
 import { TRAFFIC_TIMING_ENABLED, DOT_HEIGHT_OFFSET } from './policy.js';
 
 export function createTiming({ state: layerState, services, parts, source }) {
@@ -190,7 +190,7 @@ export function createTiming({ state: layerState, services, parts, source }) {
    * waypoint-materialization time independently.
    */
 
-  function parseRoadsTimed(roadData, trace, parsedBySource) {
+  function parseRoadsTimed(roadData, trace) {
     /* TRACE_ONLY_BEGIN */
     const _trafficTimingState = trafficTimingPass(
       trace,
@@ -231,19 +231,11 @@ export function createTiming({ state: layerState, services, parts, source }) {
     }
 
     const roads = [];
-    const floorAt = floorCellReader(services.ground);
     /* TRACE_ONLY_BEGIN */
     let _trafficTimingWaypointMaterializationMs = 0;
     /* TRACE_ONLY_END */
     for (const road of roadData.roads) {
       if (!road.coordinates || road.coordinates.length < 2) continue;
-      // A replacing snapshot repeats records this load already parsed.
-      const known = parsedBySource?.get(road);
-      if (known) {
-        for (const parsed of known) roads.push(parsed);
-        continue;
-      }
-      const first = roads.length;
 
       for (const coords of roadSurfaceChunks(road.coordinates)) {
         const type = road.type;
@@ -253,7 +245,7 @@ export function createTiming({ state: layerState, services, parts, source }) {
         const _trafficTimingMaterializeStart = performance.now();
         /* TRACE_ONLY_END */
         const waypoints = coords.map(([lng, lat]) => {
-          const floor = floorAt(lat, lng);
+          const floor = services.ground?.cachedGroundFloor?.(lat, lng);
           const h =
             (Number.isFinite(floor) && Math.abs(floor) <= 9000
               ? floor
@@ -287,7 +279,6 @@ export function createTiming({ state: layerState, services, parts, source }) {
             flow: road.flow || null,
           });
       }
-      parsedBySource?.set(road, roads.slice(first));
     }
     /* TRACE_ONLY_BEGIN */
     const _trafficTimingMetrics = {