docs(changelog): add the #1710 fragment

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

changelog.d/1706-alpr-anchor-sampling.md

@@ -1,4 +0,0 @@
-- ALPR camera badges no longer take depth samples while the overlay paints, or
-  again each time the layer is switched back on. On a terrain globe their
-  height comes from the loaded terrain and is remembered per camera; some
-  badges move a few metres onto the drawn surface (mazy1998, #1706).

changelog.d/1710-cctv-still-render-hold.md

@@ -0,0 +1,3 @@
+- A still-image CCTV camera no longer keeps the scene rendering 60 times a
+  second. Only a video feed holds continuous rendering; a still redraws when a
+  new image arrives (mazy1998, #1710).

docs/CURRENT-STATE.md

@@ -1513,14 +1513,10 @@ tile streamed in; floors resolve before new badges appear (bounded wait), and a
 badge whose cell has not resolved clamps until it does, then moves in place.
 Overlay anchors start on the same floor and write marker properties only on
 change. Once the camera is still and tiles have settled, each overlay anchor is
-replaced once by the rendered surface under it (accepted only within -30/+40 m
-of the floor cell), so badges do not float or sink on slopes; wedge corners
-follow their own floor cells instead of staying level with the apex. The
-surface is read outside the overlay paint, one camera per frame: a terrain
-globe answers from its loaded mesh (`globe.getHeight`) and only photoreal
-tiles are depth-sampled (`scene.sampleHeight`). Answers are kept per camera
-until the map source changes, so a refresh or turning the layer off and on
-samples nothing again. Unknown bearings never acquire a wedge. The selected
+replaced once by the rendered surface under it (two depth samples per paint,
+accepted only within -30/+40 m of the floor cell), so badges do not float or
+sink on slopes; wedge corners follow their own floor cells instead of staying
+level with the apex. Unknown bearings never acquire a wedge. The selected
 card's `DIRECTION` wraps after rounding to whole degrees, so a mapped bearing
 of 359.5° or more reads `0°` rather than `360°`. The row reads
 `N nearby · M on screen`; when every loaded camera is outside the view it adds

src/layers/alpr/overlay.js

@@ -4,10 +4,10 @@ import {
   MARKER_ICON_SIZE,
   SELECTED_MARKER_ICON_SIZE,
   MARKER_FLOOR_LIFT_M,
-  REMEMBERED_ANCHORS,
+  ANCHOR_SAMPLES_PER_PAINT,
   SURFACE_BELOW_FLOOR_M,
   SURFACE_ABOVE_FLOOR_M,
-  SURFACE_SAMPLES_PER_FRAME,
+  SURFACE_SAMPLES_PER_PAINT,
 } from './policy.js';
 import {
   MARKER_IMAGE,
@@ -19,17 +19,11 @@ import {
   validAlprGroundHeight,
 } from './visuals.js';
 
-const nextAnimationFrame = (step) =>
-  typeof requestAnimationFrame === 'function'
-    ? requestAnimationFrame(step)
-    : setTimeout(step, 16);
-
 /** Per-layer presentation on a caller-owned overlay; Cesium remains the fallback. */
 export function createAlprOverlay({
   state,
   services,
   onSurfaceChange = () => {},
-  requestFrame = nextAnimationFrame,
 }) {
   let lane,
     removeMapListener,
@@ -39,12 +33,7 @@ export function createAlprOverlay({
     hits = [],
     images = [],
     destroyed = false,
-    lastCamera = null,
-    sampling = false;
-  // Rendered-surface answers by camera id. Entities are rebuilt by a refresh
-  // and by turning the layer off and on; keeping the answers on them meant
-  // every rebuild sampled the same cameras again.
-  const surfaceAnswers = new Map();
+    lastCamera = null;
   const requestPaint = () => {
     if (!destroyed && state.enabled) lane?.requestPaint();
   };
@@ -103,72 +92,38 @@ export function createAlprOverlay({
       entity.gevAlprDisplayPosition = null;
       nativeVisible(entity, true);
     }
-    surfaceAnswers.clear();
     state.lastAnchorSampleAt = 0;
     retryUntil = Date.now() + 15000;
     requestPaint();
   }
 
-  function rememberSurface(record, height, checked) {
-    surfaceAnswers.delete(record.id);
-    surfaceAnswers.set(record.id, {
-      latitude: record.latitude,
-      longitude: record.longitude,
-      height,
-      checked,
-    });
-    if (surfaceAnswers.size > REMEMBERED_ANCHORS)
-      surfaceAnswers.delete(surfaceAnswers.keys().next().value);
-  }
-
-  /**
-   * Rendered surface height under a camera. A terrain globe answers from its
-   * loaded mesh; only photoreal tiles need `sampleHeight`, which renders depth
-   * and compiles its shaders on first use (a freeze of up to 1.9 s at load).
-   */
-  function surfaceHeight(record, entity) {
+  function anchorFor(record, entity, budget) {
+    if (entity.gevAlprCanvasPosition) return entity.gevAlprCanvasPosition;
     const scene = state.viewer.scene;
     const location = Cesium.Cartographic.fromDegrees(
       record.longitude,
       record.latitude,
     );
-    if (scene.globe?.show) return scene.globe.getHeight?.(location);
-    if (!scene.sampleHeightSupported) return undefined;
-    try {
-      return scene.sampleHeight(location, [entity]);
-    } catch {
-      /* streaming tiles */
-      return undefined;
-    }
-  }
-
-  /** The anchor a paint can have without sampling, or null while it waits for one. */
-  function anchorFor(record, entity) {
-    if (entity.gevAlprCanvasPosition) return entity.gevAlprCanvasPosition;
-    const scene = state.viewer.scene;
-    const answer = surfaceAnswers.get(record.id);
-    if (
-      answer?.latitude === record.latitude &&
-      answer.longitude === record.longitude
-    ) {
-      setAnchor(record, entity, answer.height);
-      if (answer.checked)
-        entity.gevAlprSurfaceCheckedFor = entity.gevAlprCanvasPosition;
-      return entity.gevAlprCanvasPosition;
-    }
-    // A floor-placed marker anchors where its native badge sits. A marker
-    // still waiting for its floor reads the terrain globe, or on photoreal
-    // tiles waits for sampleAnchors().
+    // A floor-placed marker anchors where its native badge sits; only a
+    // marker still waiting for its floor samples the rendered surface, and
+    // each paint samples a few at most (each sample is a depth render).
     let height;
     const floor = services.groundFloor.cachedGroundFloor(
       record.latitude,
       record.longitude,
     );
     if (validAlprGroundHeight(floor)) height = floor + MARKER_FLOOR_LIFT_M;
-    else if (scene.globe.show)
-      height = scene.globe.getHeight?.(
-        Cesium.Cartographic.fromDegrees(record.longitude, record.latitude),
-      );
+    else if (scene.sampleHeightSupported) {
+      if (budget.samples <= 0) return null;
+      budget.samples -= 1;
+      try {
+        height = scene.sampleHeight(location, [entity]);
+      } catch {
+        /* streaming tiles */
+      }
+    }
+    if (!validAlprGroundHeight(height) && scene.globe.show)
+      height = scene.globe.getHeight?.(location);
     if (!validAlprGroundHeight(height)) return null;
     setAnchor(record, entity, height);
     return entity.gevAlprCanvasPosition;
@@ -203,19 +158,14 @@ export function createAlprOverlay({
   }
 
   /**
-   * Sample the rendered surface for the overlay cameras, outside the paint.
-   *
-   * A camera with no floor yet gets its anchor from a sample. An anchored one
-   * is checked against the surface once: floors come from ~111 m cells, so on
-   * a slope a badge could float or sink by tens of metres. Checks run only
-   * while the camera is still and tiles have settled, and samples far outside
-   * the floor prior (a roof or a streaming tile) are rejected. Each frame
-   * takes SURFACE_SAMPLES_PER_FRAME samples, so no frame carries the whole
-   * cohort; sampling inside paint() put up to six depth renders in one frame.
+   * Replace floor anchors with the rendered surface under each overlay camera.
+   * Floors come from ~111 m cells, so on a slope a badge could float or sink
+   * by tens of metres. Runs only while the camera is still and tiles have
+   * settled, a few depth samples per paint, and each anchor at most once;
+   * samples far outside the floor prior (a roof or a streaming tile) are
+   * rejected. Returns whether anchors remain to check.
    */
-  function sampleAnchors() {
-    sampling = false;
-    if (destroyed || !state.enabled) return;
+  function refineAnchors(budget) {
     const camera = state.viewer.camera;
     const scene = state.viewer.scene;
     const still =
@@ -238,41 +188,27 @@ export function createAlprOverlay({
         position: Cesium.Cartesian3.clone(camera.positionWC),
         direction: Cesium.Cartesian3.clone(camera.directionWC),
       };
-    const canSample = scene.globe?.show || scene.sampleHeightSupported;
-    let samples = SURFACE_SAMPLES_PER_FRAME,
-      pending = false,
-      progressed = false,
-      moved = false;
-    // Cameras with no anchor come first: they are not on the overlay yet.
-    for (const record of records) {
-      const entity = state.dataSource.entities.getById(record.id);
-      if (!entity || entity.gevAlprCanvasPosition) continue;
-      // The floor may have resolved since the paint that found none.
-      if (anchorFor(record, entity)) moved = true;
-      else if (!canSample || samples <= 0) pending = true;
-      else {
-        samples -= 1;
-        const sample = surfaceHeight(record, entity);
-        if (validAlprGroundHeight(sample)) {
-          setAnchor(record, entity, sample);
-          rememberSurface(record, sample, false);
-          moved = progressed = true;
-        } else pending = true;
-      }
-    }
+    if (!scene.sampleHeightSupported) return false;
+    let pending = false;
     for (const record of records) {
       const entity = state.dataSource.entities.getById(record.id);
       const anchor = entity?.gevAlprCanvasPosition;
-      if (!anchor || !canSample || entity.gevAlprSurfaceCheckedFor === anchor)
-        continue;
-      if (!still || !surfaceSettled(scene) || samples <= 0) {
+      if (!anchor || entity.gevAlprSurfaceCheckedFor === anchor) continue;
+      if (!still || !surfaceSettled(scene) || budget.samples <= 0) {
         pending = true;
         continue;
       }
-      samples -= 1;
-      progressed = true;
-      const sample = surfaceHeight(record, entity);
-      let height = Cesium.Cartographic.fromCartesian(anchor).height;
+      budget.samples -= 1;
+      let sample;
+      try {
+        sample = scene.sampleHeight(
+          Cesium.Cartographic.fromDegrees(record.longitude, record.latitude),
+          [entity],
+        );
+      } catch {
+        /* streaming tiles */
+      }
+      const current = Cesium.Cartographic.fromCartesian(anchor).height;
       const floor = services.groundFloor.cachedGroundFloor(
         record.latitude,
         record.longitude,
@@ -282,43 +218,21 @@ export function createAlprOverlay({
         (!validAlprGroundHeight(floor) ||
           (sample >= floor - SURFACE_BELOW_FLOOR_M &&
             sample <= floor + SURFACE_ABOVE_FLOOR_M));
-      if (accepted && Math.abs(sample + MARKER_FLOOR_LIFT_M - height) > 1) {
-        height = sample + MARKER_FLOOR_LIFT_M;
-        setAnchor(record, entity, height);
-        moved = true;
-      }
+      if (accepted && Math.abs(sample + MARKER_FLOOR_LIFT_M - current) > 1)
+        setAnchor(record, entity, sample + MARKER_FLOOR_LIFT_M);
       entity.gevAlprSurfaceCheckedFor = entity.gevAlprCanvasPosition;
-      // A surface that did not answer is asked again after a rebuild.
-      if (validAlprGroundHeight(sample)) rememberSurface(record, height, true);
       if (entity.id === state.selectedId)
         entity.gevAlprDisplayPosition = entity.gevAlprCanvasPosition;
     }
-    if (moved) requestPaint();
-    if (!pending || Date.now() >= retryUntil) return;
-    // Take the next ration on the next frame; when nothing could be sampled
-    // (camera moving, tiles streaming, no floor yet) look again in 250 ms.
-    if (progressed) scheduleSampling();
-    else if (!retryTimer)
-      retryTimer = setTimeout(() => {
-        retryTimer = null;
-        scheduleSampling();
-      }, 250);
-  }
-
-  function scheduleSampling() {
-    if (sampling || destroyed) return;
-    sampling = true;
-    requestFrame(sampleAnchors);
+    return pending;
   }
 
   function paint({ ctx, width, height, keyhole, occluder }) {
     hits = [];
     if (!state.enabled || destroyed) return;
-    let waiting = false;
+    let unresolved = false;
     const painted = [];
-    const canSample =
-      state.viewer.scene.globe?.show ||
-      state.viewer.scene.sampleHeightSupported;
+    const budget = { samples: ANCHOR_SAMPLES_PER_PAINT };
     for (const record of records) {
       const entity = state.dataSource.entities.getById(record.id);
       if (!entity) continue;
@@ -332,14 +246,12 @@ export function createAlprOverlay({
         nativeVisible(entity, true);
         continue;
       }
-      const anchor = anchorFor(record, entity);
+      const anchor = anchorFor(record, entity, budget);
       if (!anchor) {
         nativeVisible(entity, true);
-        waiting = true;
+        unresolved = true;
         continue;
       }
-      if (canSample && entity.gevAlprSurfaceCheckedFor !== anchor)
-        waiting = true;
       canvasOwned(entity, true);
       if (occluder && !occluder.isPointVisible(anchor)) {
         setShown(entity, false);
@@ -423,9 +335,15 @@ export function createAlprOverlay({
       ctx.restore();
       hits.push({ id: record.id, x: origin.x, y: origin.y, radius: size / 2 });
     }
-    // Anchors still to find or to check are sampled after this paint, a few
-    // per frame, never inside it.
-    if (waiting && !retryTimer && Date.now() < retryUntil) scheduleSampling();
+    const refining = refineAnchors({
+      samples: Math.min(budget.samples, SURFACE_SAMPLES_PER_PAINT),
+    });
+    if ((unresolved || refining) && !retryTimer && Date.now() < retryUntil) {
+      retryTimer = setTimeout(() => {
+        retryTimer = null;
+        requestPaint();
+      }, 250);
+    }
   }
 
   return {

src/layers/alpr/overlay.test.mjs

@@ -45,10 +45,8 @@ function harness(t, count = 2, { floor = null } = {}) {
     active,
     removed = 0,
     paints = 0;
-  const frames = [];
   const overlay = createAlprOverlay({
     state,
-    requestFrame: (step) => frames.push(step),
     services: {
       groundFloor: { cachedGroundFloor: () => floor },
       overlays: {
@@ -108,12 +106,6 @@ function harness(t, count = 2, { floor = null } = {}) {
     entities,
     draw,
     paint: (occluder) => paint({ ctx, width: 800, height: 600, occluder }),
-    /** Run the sampling step queued for the next animation frame, if any. */
-    frame() {
-      const step = frames.shift();
-      step?.();
-      return Boolean(step);
-    },
     mapChanged() {
       mapListener({ detail: { status: 'ready' } });
     },
@@ -251,149 +243,41 @@ test('overlay glyphs and native badges shrink alike with distance', () => {
   assert.ok(Math.abs(markerScale(20_250) - 0.8) < 1e-9);
 });
 
-/** A photoreal scene: no globe, the rendered surface read by depth samples. */
-function photoreal(h, heightAt = () => 172) {
-  const scene = h.state.viewer.scene;
-  h.state.viewer.camera.directionWC = Cesium.Cartesian3.UNIT_X;
-  scene.globe.show = false;
-  scene.sampleHeightSupported = true;
-  scene.primitives = { length: 0, get: () => null };
-  const sampled = [];
-  scene.sampleHeight = (carto) => {
-    sampled.push(carto);
-    return heightAt(Cesium.Math.toDegrees(carto.latitude));
-  };
-  return sampled;
-}
-
-const anchorHeight = (h, id) =>
-  Cesium.Cartographic.fromCartesian(
-    h.entities.getById(id).gevAlprCanvasPosition,
-  ).height;
-
-/** Run sampling frames until none is queued, waiting out the 250 ms look-again. */
-function settle(t, h) {
-  for (let i = 0; i < 400; i++) if (!h.frame()) t.mock.timers.tick(250);
-}
-
 test('a still view replaces floor anchors with the rendered surface, within the floor window', (t) => {
   // Floors come from ~111 m cells; on a slope a badge floated above the mesh.
-  t.mock.timers.enable({ apis: ['setTimeout', 'Date'] });
   const h = harness(t, 2, { floor: 150 });
-  const sampled = photoreal(h, (latitude) => (latitude > 30.00005 ? 400 : 172));
+  const scene = h.state.viewer.scene;
+  const camera = h.state.viewer.camera;
+  camera.directionWC = Cesium.Cartesian3.UNIT_X;
+  scene.sampleHeightSupported = true;
+  scene.primitives = { length: 0, get: () => null };
+  let samples = 0;
+  scene.sampleHeight = (carto) => {
+    samples++;
+    return Cesium.Math.toDegrees(carto.latitude) > 30.00005 ? 400 : 172;
+  };
   h.overlay.sync(h.records);
   h.paint();
-  assert.ok(
-    Math.abs(anchorHeight(h, 'camera:0') - 151.5) < 0.01,
-    'floor anchor first',
-  );
-  assert.equal(h.frame(), true, 'the paint queued a sampling frame');
+  const height = (id) =>
+    Cesium.Cartographic.fromCartesian(
+      h.entities.getById(id).gevAlprCanvasPosition,
+    ).height;
   assert.equal(
-    sampled.length,
+    samples,
     0,
     'no depth samples while the camera may still be moving',
   );
-  settle(t, h);
+  assert.ok(Math.abs(height('camera:0') - 151.5) < 0.01, 'floor anchor first');
+  h.paint();
   assert.ok(
-    Math.abs(anchorHeight(h, 'camera:0') - 173.5) < 0.01,
+    Math.abs(height('camera:0') - 173.5) < 0.01,
     'rendered surface once still',
   );
   assert.ok(
-    Math.abs(anchorHeight(h, 'camera:1') - 151.5) < 0.01,
+    Math.abs(height('camera:1') - 151.5) < 0.01,
     'a rooftop-height sample is rejected',
   );
-  assert.equal(sampled.length, 2);
+  const taken = samples;
   h.paint();
-  settle(t, h);
-  assert.equal(sampled.length, 2, 'each anchor is checked once');
-});
-
-test('a paint never samples the surface; frames take one sample each', (t) => {
-  // Sampling inside paint() put up to six depth renders into one frame, and
-  // the first of them compiles shaders: a freeze of 0.8 to 1.9 s at load.
-  t.mock.timers.enable({ apis: ['setTimeout', 'Date'] });
-  const h = harness(t, 8);
-  const sampled = photoreal(h);
-  h.overlay.sync(h.records);
-  h.paint();
-  h.paint();
-  assert.equal(sampled.length, 0, 'no sample inside a paint');
-  assert.equal(h.draw.length, 0, 'unanchored cameras keep their native badge');
-  for (let taken = 1; taken <= 8; taken++) {
-    assert.equal(h.frame(), true);
-    assert.equal(sampled.length, taken, 'one sample per frame');
-  }
-  for (const record of h.records)
-    assert.ok(Math.abs(anchorHeight(h, record.id) - 172) < 0.01);
-  h.paint();
-  assert.ok(h.draw.length > 0, 'anchored cameras paint on the overlay');
-});
-
-test('a terrain globe is read from its mesh, never depth-sampled', (t) => {
-  t.mock.timers.enable({ apis: ['setTimeout', 'Date'] });
-  const h = harness(t, 3, { floor: 150 });
-  const sampled = photoreal(h);
-  const scene = h.state.viewer.scene;
-  scene.globe.show = true;
-  scene.globe.tilesLoaded = true;
-  let reads = 0;
-  scene.globe.getHeight = () => {
-    reads++;
-    return 172;
-  };
-  h.overlay.sync(h.records);
-  h.paint();
-  settle(t, h);
-  assert.equal(sampled.length, 0);
-  assert.equal(reads, 3);
-  // The same anchor the depth sample gave: the surface plus the marker lift.
-  for (const record of h.records)
-    assert.ok(Math.abs(anchorHeight(h, record.id) - 173.5) < 0.01);
-});
-
-test('surface answers outlive rebuilt markers and a re-enable, until the map changes', (t) => {
-  t.mock.timers.enable({ apis: ['setTimeout', 'Date'] });
-  const h = harness(t, 4, { floor: 150 });
-  const sampled = photoreal(h);
-  h.overlay.sync(h.records);
-  h.paint();
-  settle(t, h);
-  assert.equal(sampled.length, 4);
-  const before = h.records.map((record) => anchorHeight(h, record.id));
-
-  // A refresh or a toggle removes the entities and builds new ones.
-  const rebuild = () => {
-    h.overlay.clear();
-    h.entities.removeAll();
-    for (const record of h.records)
-      h.entities.add({
-        id: record.id,
-        billboard: { image: 'fallback', show: true },
-        polyline: { show: true },
-        polygon: { show: true },
-      });
-    h.overlay.sync(h.records);
-    h.paint();
-    settle(t, h);
-  };
-  rebuild();
-  h.state.enabled = false;
-  h.overlay.clear();
-  h.state.enabled = true;
-  rebuild();
-  assert.equal(sampled.length, 4, 'no camera is sampled again');
-  assert.deepEqual(
-    h.records.map((record) => anchorHeight(h, record.id)),
-    before,
-  );
-
-  // A camera that moved is a different question.
-  h.records[0] = { ...h.records[0], latitude: h.records[0].latitude + 0.001 };
-  rebuild();
-  assert.equal(sampled.length, 5);
-
-  h.mapChanged();
-  h.paint();
-  settle(t, h);
-  assert.equal(sampled.length, 9, 'a new map surface is sampled afresh');
+  assert.equal(samples, taken, 'each anchor is checked once');
 });

src/layers/alpr/policy.js

@@ -66,15 +66,14 @@ export const MAX_CANVAS_FRUSTUMS = 64;
 /** Metres a floor-placed marker sits above its resolved ground cell. */
 export const MARKER_FLOOR_LIFT_M = 1.5;
 
-/** Rendered-surface samples one frame may take (on photoreal tiles each is a
- * depth render of several milliseconds, so they are spread over frames). */
-export const SURFACE_SAMPLES_PER_FRAME = 1;
-/** Surface answers kept by camera id, so a refresh or re-enable asks nothing. */
-export const REMEMBERED_ANCHORS = 2048;
+/** Rendered-surface samples one overlay paint may take (each is a depth render). */
+export const ANCHOR_SAMPLES_PER_PAINT = 4;
 
 /** Accepted rendered-surface window around a floor cell (a cut or an embankment
  * sits within it; a rooftop or an unstreamed tile usually does not). */
 export const SURFACE_BELOW_FLOOR_M = 30;
+/** Rendered-surface refinements per paint while the camera is still. */
+export const SURFACE_SAMPLES_PER_PAINT = 2;
 export const SURFACE_ABOVE_FLOOR_M = 40;
 
 /** OSM attribution may collapse after five seconds; full credit stays in Data attribution. */

src/layers/cctv/frames.js

@@ -144,33 +144,35 @@ export function createFrames({ state: layerState, services, parts, source }) {
    * the double-buffer canvas reference, throttled to PROJECTION_TEXTURE_SWAP_MS.
    *
    * @param {Object} record - Camera record with an initialized projection runtime.
+   * @returns {boolean} Whether a new image was put on the plane.
    */
 
   function refreshProjectionTextures(record) {
     const runtime = record?.projection;
-    if (!runtime || runtime.mode === 'video') return;
+    if (!runtime || runtime.mode === 'video') return false;
     const now = Date.now();
     if (
       now - parts.model.safeNumber(runtime.lastTextureSwapAt, 0) <
       PROJECTION_TEXTURE_SWAP_MS
     )
-      return;
+      return false;
 
     const planeShowing = !!(runtime.planeEntity?.show && runtime.planeMaterial);
-    if (!planeShowing) return;
+    if (!planeShowing) return false;
 
     // Only swap when the canvas content actually changed since the last swap.
     // Frames land every ~10 s but this runs at 1 Hz — swapping an UNCHANGED
     // canvas re-uploads the texture for nothing, and each material image
     // reassignment is a flash opportunity on the live plane (owner field test
     // 2026-07-04: intermittent white flashes on the monitor plane).
-    if (runtime.canvasStamp === runtime.lastSwappedCanvasStamp) return;
+    if (runtime.canvasStamp === runtime.lastSwappedCanvasStamp) return false;
 
     const buffer = paintNextProjectionBuffer(runtime);
-    if (!buffer) return;
+    if (!buffer) return false;
     runtime.lastTextureSwapAt = now;
     runtime.lastSwappedCanvasStamp = runtime.canvasStamp;
     runtime.planeMaterial.image = buffer;
+    return true;
   }
 
   /**

src/layers/cctv/policy.js

@@ -123,6 +123,11 @@ export const CCTV_CALIBRATION_STORAGE_KEY_V2 =
 
 export const PROJECTION_TEXTURE_SWAP_MS = 1000;
 
+// A still-image projection changes only when a new still is swapped onto the
+// plane, so the scene renders for this long after a swap (Cesium binds the new
+// image over the next frames) and is otherwise left idle.
+export const PROJECTION_SWAP_RENDER_MS = 500;
+
 // V2 frustum geometry (design §2a/§6): the far-cap center + corners never sink
 // below groundAlt + this clearance, so a fabricated pitch (-24°) cannot bury
 // the monitor plane in the 3D tiles. Exported for the unit suite.

src/layers/cctv/projection.js

@@ -6,6 +6,7 @@ import {
   PLANE_OUTLINE_COLOR,
   PROJECTION_CANVAS_WIDTH,
   PROJECTION_CANVAS_HEIGHT,
+  PROJECTION_SWAP_RENDER_MS,
 } from './policy.js';
 
 export function createProjection({
@@ -14,7 +15,15 @@ export function createProjection({
   parts,
   source,
 }) {
-  const { holdContinuousRender, releaseContinuousRender } = services.render;
+  const {
+    holdContinuousRender,
+    releaseContinuousRender,
+    governorRequestRender = () => {},
+  } = services.render;
+  // Until this time (performance.now) the projection loop asks for a frame on
+  // every tick: after a still is swapped onto the plane, and after an edge
+  // that re-arms the loop (activation, projection shown).
+  let renderUntil = 0;
 
   /**
    * Build the protected label associated with one active monitor plane.
@@ -352,12 +361,9 @@ export function createProjection({
   }
 
   function startProjectionLoop() {
+    renderUntil = performance.now() + PROJECTION_SWAP_RENDER_MS;
     if (layerState._projectionRaf) return;
     if (!parts.model.projectionLoopIsNeeded()) return;
-    // The armed projection loop uploads video textures / runs focus fades per
-    // frame — the scene must render continuously while it runs. Released when
-    // the tick self-stops. (perf wave 2)
-    holdContinuousRender('cctv-projection');
 
     const tick = () => {
       if (!layerState._viewer || !parts.model.projectionLoopIsNeeded()) {
@@ -366,15 +372,30 @@ export function createProjection({
         return;
       }
 
-      parts.rendering.refreshCctvFocusStyles(performance.now());
+      const now = performance.now();
+      const restyled = parts.rendering.refreshCctvFocusStyles(now);
 
       const active = parts.selection.getActiveRecord();
+      let video = false;
       if (layerState._enabled && layerState._showProjection && active) {
         ensureProjectionRuntime(active);
         if (active.projection && !active.projection.video) {
           parts.frames.drawProjectionFrame(active);
-          parts.frames.refreshProjectionTextures(active);
-        }
+          if (parts.frames.refreshProjectionTextures(active))
+            renderUntil = now + PROJECTION_SWAP_RENDER_MS;
+        } else video = Boolean(active.projection?.video);
+      }
+
+      // Only a video feed changes the scene on every frame, so only video
+      // holds the continuous loop. A still lands about every ten seconds and
+      // a focus fade restyles icons every 80 ms; each asks for the frames it
+      // needs. Holding for stills rendered the scene 60 times a second for as
+      // long as a camera was active. (perf wave 2 held for both.)
+      if (video) holdContinuousRender('cctv-projection');
+      else {
+        releaseContinuousRender('cctv-projection');
+        if (restyled || now < renderUntil)
+          governorRequestRender('cctv-projection');
       }
 
       layerState._projectionRaf = requestAnimationFrame(tick);

src/layers/cctv/projectionLoop.test.mjs

@@ -0,0 +1,211 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { createProjection } from './projection.js';
+import { createFrames } from './frames.js';
+import {
+  PROJECTION_SWAP_RENDER_MS,
+  PROJECTION_TEXTURE_SWAP_MS,
+} from './policy.js';
+
+/** The projection loop on a hand-cranked clock, with the render governor's calls recorded. */
+function harness(t, { video = false, showProjection = true } = {}) {
+  let clock = 1000;
+  const frames = [];
+  const original = {
+    now: performance.now,
+    request: globalThis.requestAnimationFrame,
+    cancel: globalThis.cancelAnimationFrame,
+  };
+  performance.now = () => clock;
+  globalThis.requestAnimationFrame = (step) => frames.push(step);
+  globalThis.cancelAnimationFrame = () => frames.splice(0);
+  t.after(() => {
+    performance.now = original.now;
+    globalThis.requestAnimationFrame = original.request;
+    globalThis.cancelAnimationFrame = original.cancel;
+  });
+
+  const holds = new Set();
+  const calls = { hold: 0, requests: 0, draws: 0 };
+  const record = {
+    camera: { id: 'cam-1' },
+    projection: { video: video ? {} : null, mode: video ? 'video' : 'image' },
+  };
+  const scene = { needed: true, swap: false, restyled: false };
+  const state = {
+    _viewer: {},
+    _enabled: true,
+    _showProjection: showProjection,
+    _projectionRaf: 0,
+    _projectionEntities: [],
+  };
+  const projection = createProjection({
+    state,
+    services: {
+      render: {
+        holdContinuousRender(owner) {
+          calls.hold++;
+          holds.add(owner);
+        },
+        releaseContinuousRender: (owner) => holds.delete(owner),
+        governorRequestRender: () => calls.requests++,
+      },
+    },
+    parts: {
+      model: { projectionLoopIsNeeded: () => scene.needed },
+      rendering: { refreshCctvFocusStyles: () => scene.restyled },
+      selection: { getActiveRecord: () => record },
+      frames: {
+        drawProjectionFrame: () => calls.draws++,
+        refreshProjectionTextures() {
+          const swapped = scene.swap;
+          scene.swap = false;
+          return swapped;
+        },
+      },
+    },
+    source: {},
+  });
+  return {
+    projection,
+    state,
+    record,
+    scene,
+    holds,
+    calls,
+    /** Run `count` animation frames 16 ms apart; returns the frames requested in them. */
+    run(count = 1) {
+      const before = calls.requests;
+      for (let i = 0; i < count; i++) {
+        clock += 16;
+        frames.shift()?.();
+      }
+      return calls.requests - before;
+    },
+    advance(ms) {
+      clock += ms;
+    },
+    get queued() {
+      return frames.length;
+    },
+  };
+}
+
+test('a still-image camera never holds the continuous render loop', (t) => {
+  const h = harness(t);
+  h.projection.startProjectionLoop();
+  h.run(600);
+  assert.equal(h.calls.hold, 0);
+  assert.equal(h.holds.size, 0);
+  assert.equal(h.calls.draws, 600, 'the loop still polls for a new still');
+  assert.equal(h.queued, 1, 'and stays armed');
+});
+
+test('a new still on the plane is rendered, then the scene goes idle again', (t) => {
+  const h = harness(t);
+  h.projection.startProjectionLoop();
+  // Arming the loop (activation, projection shown) renders its first frames.
+  assert.ok(h.run(5) === 5);
+  h.advance(PROJECTION_SWAP_RENDER_MS);
+  assert.equal(h.run(120), 0, 'an unchanged still asks for no frame');
+
+  h.scene.swap = true;
+  assert.equal(h.run(1), 1, 'the tick that swaps the image asks for a frame');
+  const settling = Math.floor(PROJECTION_SWAP_RENDER_MS / 16) - 2;
+  assert.equal(h.run(settling), settling, 'and so do the ticks while it binds');
+  h.advance(PROJECTION_SWAP_RENDER_MS);
+  assert.equal(h.run(120), 0);
+  assert.equal(h.holds.size, 0);
+});
+
+test('activating another camera while the loop runs renders its first frames', (t) => {
+  const h = harness(t);
+  h.projection.startProjectionLoop();
+  h.advance(PROJECTION_SWAP_RENDER_MS * 2);
+  assert.equal(h.run(10), 0);
+  h.projection.startProjectionLoop();
+  assert.equal(h.run(10), 10);
+  assert.equal(h.queued, 1, 'still one loop');
+});
+
+test('a video camera holds continuous render until it stops being video', (t) => {
+  const h = harness(t, { video: true });
+  h.projection.startProjectionLoop();
+  h.run(3);
+  assert.deepEqual([...h.holds], ['cctv-projection']);
+  assert.equal(h.calls.draws, 0, 'Cesium updates the video texture itself');
+  // The stream failed over to stills.
+  h.record.projection.video = null;
+  h.run(1);
+  assert.equal(h.holds.size, 0);
+  h.record.projection.video = {};
+  h.run(1);
+  assert.deepEqual([...h.holds], ['cctv-projection']);
+  h.projection.stopProjectionLoop();
+  assert.equal(h.holds.size, 0);
+});
+
+test('a focus fade asks for a frame only on the ticks that restyle an icon', (t) => {
+  const h = harness(t, { showProjection: false });
+  h.projection.startProjectionLoop();
+  h.advance(PROJECTION_SWAP_RENDER_MS * 2);
+  assert.equal(h.run(10), 0);
+  h.scene.restyled = true;
+  assert.equal(h.run(4), 4);
+  h.scene.restyled = false;
+  assert.equal(h.run(10), 0);
+  assert.equal(h.holds.size, 0);
+});
+
+test('the loop releases and stops when it has no work', (t) => {
+  const h = harness(t, { video: true });
+  h.projection.startProjectionLoop();
+  h.run(2);
+  h.scene.needed = false;
+  h.run(1);
+  assert.equal(h.holds.size, 0);
+  assert.equal(h.state._projectionRaf, 0);
+  assert.equal(h.queued, 0);
+});
+
+test('refreshProjectionTextures reports whether it put a new image on the plane', (t) => {
+  const previousDocument = globalThis.document;
+  globalThis.document = {
+    createElement: () => ({
+      getContext: () => ({ clearRect() {}, drawImage() {} }),
+    }),
+  };
+  t.after(() => {
+    if (previousDocument === undefined) delete globalThis.document;
+    else globalThis.document = previousDocument;
+  });
+  const frames = createFrames({
+    state: {},
+    services: {},
+    parts: { model: { safeNumber: (value, fallback) => value ?? fallback } },
+    source: {},
+  });
+  const runtime = {
+    mode: 'image',
+    canvas: {},
+    canvasStamp: 1,
+    planeEntity: { show: true },
+    planeMaterial: { image: null },
+  };
+  const record = { projection: runtime };
+  assert.equal(frames.refreshProjectionTextures(record), true);
+  const first = runtime.planeMaterial.image;
+  assert.ok(first);
+  // Unchanged canvas: nothing to render.
+  runtime.lastTextureSwapAt -= PROJECTION_TEXTURE_SWAP_MS;
+  assert.equal(frames.refreshProjectionTextures(record), false);
+  assert.equal(runtime.planeMaterial.image, first);
+  runtime.canvasStamp = 2;
+  assert.equal(frames.refreshProjectionTextures(record), true);
+  assert.notEqual(runtime.planeMaterial.image, first);
+  runtime.planeEntity.show = false;
+  runtime.canvasStamp = 3;
+  runtime.lastTextureSwapAt -= PROJECTION_TEXTURE_SWAP_MS;
+  assert.equal(frames.refreshProjectionTextures(record), false);
+  assert.equal(frames.refreshProjectionTextures({ projection: { mode: 'video' } }), false);
+});

src/layers/cctv/rendering.js

@@ -61,8 +61,8 @@ export function createRendering({
       !layerState._viewer ||
       !focusPassIsNeeded(target, layerState._activeFocusStyleCount)
     )
-      return;
-    if (nowMs - layerState._lastFocusStyleAt < 80) return;
+      return false;
+    if (nowMs - layerState._lastFocusStyleAt < 80) return false;
     layerState._lastFocusStyleAt = nowMs;
     const scene = layerState._viewer.scene;
     const camera = layerState._viewer.camera;
@@ -82,6 +82,8 @@ export function createRendering({
       baseColorFor: cameraColorFor,
     });
     layerState._activeFocusStyleCount = result.activeCount;
+    // Whether an icon was restyled, so the caller can ask for a frame.
+    return result.writes > 0;
   }
 
   /**