diff --git a/src/styles/bloomPasses.test.mjs b/src/styles/bloomPasses.test.mjs
new file mode 100644
index 000000000..695d40c52
--- /dev/null
+++ b/src/styles/bloomPasses.test.mjs
@@ -0,0 +1,93 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { nightVisionShader } from './surveillance.js';
+import { thermalShader } from './thermal.js';
+
+/**
+ * Texture reads one pixel costs: every `texture(` call, multiplied by the
+ * trip counts of the `for (int v = a; v <= b; v++)` loops around it.
+ */
+function textureReads(source) {
+  const token =
+    /for \(int \w+ = (-?\d+); \w+ <= (-?\d+); \w+\+\+\) \{|texture\(|[{}]/g;
+  const scopes = [1];
+  let reads = 0;
+  for (const match of source.matchAll(token)) {
+    const inside = scopes.at(-1);
+    if (match[0] === 'texture(') reads += inside;
+    else if (match[0] === '}') scopes.pop();
+    else if (match[0] === '{') scopes.push(inside);
+    else scopes.push(inside * (Number(match[2]) - Number(match[1]) + 1));
+  }
+  assert.deepEqual(scopes, [1], 'braces balance');
+  return reads;
+}
+
+function readsPerPixel(shader) {
+  return [shader, ...(shader.passes || [])].reduce(
+    (total, pass) => total + textureReads(pass.fragmentShader),
+    0,
+  );
+}
+
+test('the read counter multiplies nested loop trips', () => {
+  const nested = `void main() {
+    for (int y = -5; y <= 5; y++) {
+      for (int x = -5; x <= 5; x++) { a += texture(t, uv).r; }
+    }
+    b = texture(t, uv);
+  }`;
+  assert.equal(textureReads(nested), 122);
+});
+
+test('night vision blooms with two 11-sample sums, not 121 samples', () => {
+  // 11 in the row pass, 11 column sums and the pixel itself.
+  assert.equal(readsPerPixel(nightVisionShader), 23);
+});
+
+test('FLIR blooms with two 9-sample sums, not 81 samples', () => {
+  // 9 in the row pass, 9 column sums, the 5x5 soft blur, the pixel itself
+  // and the centre sample behind the temperature readout.
+  assert.equal(readsPerPixel(thermalShader), 45);
+});
+
+for (const shader of [nightVisionShader, thermalShader])
+  test(`${shader.name}: each pass is fed the uniforms it declares`, () => {
+    assert.ok(shader.passes.length > 0);
+    for (const pass of shader.passes) {
+      const declared = [
+        ...pass.fragmentShader.matchAll(/uniform float (\w+);/g),
+      ].map((match) => match[1]);
+      assert.deepEqual(declared, pass.uniforms);
+      for (const uniform of pass.uniforms)
+        assert.ok(uniform in shader.uniforms, `${uniform} is a style uniform`);
+      assert.match(
+        shader.fragmentShader,
+        new RegExp(`uniform sampler2D ${pass.texture};`),
+      );
+      assert.match(
+        shader.fragmentShader,
+        new RegExp(`texture\\(${pass.texture},`),
+      );
+    }
+  });
+
+test('the row and column weights multiply back to the single-pass weight', () => {
+  // Night vision: exp(-(x² + y²) / 18). FLIR: exp(-0.5 (x² + y²) / 8).
+  const cases = [
+    [
+      5,
+      (x, y) => Math.exp(-(x * x + y * y) / 18),
+      (v) => Math.exp(-(v * v) / 18),
+    ],
+    [
+      4,
+      (x, y) => Math.exp((-0.5 * (x * x + y * y)) / 8),
+      (v) => Math.exp((-0.5 * v * v) / 8),
+    ],
+  ];
+  for (const [reach, whole, part] of cases)
+    for (let y = -reach; y <= reach; y++)
+      for (let x = -reach; x <= reach; x++)
+        assert.ok(Math.abs(whole(x, y) - part(x) * part(y)) < 1e-12);
+});
diff --git a/src/styles/surveillance.js b/src/styles/surveillance.js
index 5eae7fdd3..27cf02b50 100644
--- a/src/styles/surveillance.js
+++ b/src/styles/surveillance.js
@@ -11,8 +11,55 @@ import { msg } from '../i18n/marker.js';
  *   scanlineStr (0-1) — scanline intensity (kept for compatibility)
  *   pixelation (1-6)  — intensifier tube resolution pixelation
  */
+
+/**
+ * The bloom is an 11x11 Gaussian over samples four texels apart. Its weight
+ * exp(-(x² + y²) / 18) is a product of a row weight and a column weight, and
+ * the stage reads its input with nearest sampling, so every sample is a whole
+ * texel away from the first. This pass therefore sums the eleven samples of
+ * each row once per texel and the main pass sums eleven of those: 22 reads
+ * for each pixel where one pass took 121, with the same result.
+ *
+ * The row sum is written across two 8-bit channels (whole 255ths in red, the
+ * remainder in green) so the stage keeps the default render target.
+ */
+const NVG_BLOOM_ROWS_SHADER = /* glsl */ `
+    uniform sampler2D colorTexture;
+    uniform vec2 colorTextureDimensions;
+    uniform float gain;
+    in vec2 v_textureCoordinates;
+
+    void main() {
+      vec2 texel = 1.0 / colorTextureDimensions;
+      float gainLevel = mix(0.8, 2.5, gain);
+      float rowSum = 0.0;
+      float rowW = 0.0;
+      for (int x = -5; x <= 5; x++) {
+        vec2 offset = vec2(float(x), 0.0) * texel * 4.0;
+        float sLuma = dot(texture(colorTexture, v_textureCoordinates + offset).rgb, vec3(0.299, 0.587, 0.114));
+        float bright = smoothstep(0.4, 0.9, sLuma * gainLevel);
+        float w = exp(-float(x * x) / 18.0);
+        rowSum += bright * w;
+        rowW += w;
+      }
+      float scaled = rowSum / rowW * 255.0;
+      out_FragColor = vec4(floor(scaled) / 255.0, fract(scaled), 0.0, 1.0);
+    }
+  `;
+
 export const nightVisionShader = {
   name: 'surveillance',
+  // The film grain, scanline drift and clock digits step at this rate, and
+  // the scene is redrawn at it while the style is the only thing moving.
+  timeHz: 15,
+  passes: [
+    {
+      name: 'bloomRows',
+      texture: 'bloomRowsTexture',
+      uniforms: ['gain'],
+      fragmentShader: NVG_BLOOM_ROWS_SHADER,
+    },
+  ],
   uniforms: {
     gain: { default: 0.55, min: 0, max: 1, label: msg('Gain') },
     bloom: { default: 0.3, min: 0, max: 1, label: msg('Bloom') },
@@ -21,6 +68,7 @@ export const nightVisionShader = {
   },
   fragmentShader: /* glsl */ `
     uniform sampler2D colorTexture;
+    uniform sampler2D bloomRowsTexture;
     uniform vec2 colorTextureDimensions;
     uniform float intensity;
     uniform float time;
@@ -189,17 +237,15 @@ export const nightVisionShader = {
 
       // ── Intensifier tube bloom (THE key NVG visual) ─────
       // Bloom around bright sources — wider kernel for realistic halos
+      // Rows were summed by the bloomRows pass; the columns are summed here.
       float bloomAccum = 0.0;
       float bloomW = 0.0;
       for (int y = -5; y <= 5; y++) {
-        for (int x = -5; x <= 5; x++) {
-          vec2 offset = vec2(float(x), float(y)) * texel * 4.0;
-          float sLuma = dot(texture(colorTexture, distUV + offset).rgb, vec3(0.299, 0.587, 0.114));
-          float bright = smoothstep(0.4, 0.9, sLuma * gainLevel);
-          float w = exp(-float(x * x + y * y) / 18.0);
-          bloomAccum += bright * w;
-          bloomW += w;
-        }
+        vec2 offset = vec2(0.0, float(y)) * texel * 4.0;
+        vec2 rows = texture(bloomRowsTexture, distUV + offset).rg;
+        float w = exp(-float(y * y) / 18.0);
+        bloomAccum += (rows.r + rows.g / 255.0) * w;
+        bloomW += w;
       }
       bloomAccum /= bloomW;
 
diff --git a/src/styles/thermal.js b/src/styles/thermal.js
index f62327507..9c5a2bf92 100644
--- a/src/styles/thermal.js
+++ b/src/styles/thermal.js
@@ -13,8 +13,55 @@ import { msg } from '../i18n/marker.js';
  *   pixelation (1-6)  — sensor resolution pixelation grid size
  *   palette (0-1)     — 0 = monochrome FLIR, 1 = Ironbow "Predator" color ramp
  */
+
+/**
+ * The hot-spot bloom is a 9x9 Gaussian over samples three texels apart. Its
+ * weight is a product of a row weight and a column weight, and the stage
+ * reads its input with nearest sampling, so this pass sums the nine samples
+ * of each row once per texel and the main pass sums nine of those: 18 reads
+ * for each pixel where one pass took 81, with the same result. The row sum is
+ * written across two 8-bit channels, as in the night-vision bloom.
+ */
+const FLIR_BLOOM_ROWS_SHADER = /* glsl */ `
+    uniform sampler2D colorTexture;
+    uniform vec2 colorTextureDimensions;
+    uniform float sensitivity;
+    uniform float mode;
+    in vec2 v_textureCoordinates;
+
+    void main() {
+      vec2 texel = 1.0 / colorTextureDimensions;
+      float sens = mix(0.25, 1.0, sensitivity);
+      float isBlackHot = step(0.5, mode);
+      float rowSum = 0.0;
+      float rowW = 0.0;
+      for (int x = -4; x <= 4; x++) {
+        vec2 offset = vec2(float(x), 0.0) * texel * 3.0;
+        float sLuma = dot(texture(colorTexture, v_textureCoordinates + offset).rgb, vec3(0.299, 0.587, 0.114));
+        float sMapped = clamp((sLuma - (0.5 - sens * 0.5)) / sens, 0.0, 1.0);
+        float sFinal = mix(sMapped, 1.0 - sMapped, isBlackHot);
+        float w = exp(-0.5 * float(x * x) / 8.0);
+        rowSum += smoothstep(0.6, 1.0, sFinal) * w;
+        rowW += w;
+      }
+      float scaled = rowSum / rowW * 255.0;
+      out_FragColor = vec4(floor(scaled) / 255.0, fract(scaled), 0.0, 1.0);
+    }
+  `;
+
 export const thermalShader = {
   name: 'thermal',
+  // The drifting noise and the frame counter step at this rate, and the scene
+  // is redrawn at it while the style is the only thing moving.
+  timeHz: 15,
+  passes: [
+    {
+      name: 'bloomRows',
+      texture: 'bloomRowsTexture',
+      uniforms: ['sensitivity', 'mode'],
+      fragmentShader: FLIR_BLOOM_ROWS_SHADER,
+    },
+  ],
   uniforms: {
     sensitivity: { default: 0.75, min: 0, max: 1, label: msg('Sensitivity') },
     bloom: { default: 0.65, min: 0, max: 1, label: msg('Bloom') },
@@ -24,6 +71,7 @@ export const thermalShader = {
   },
   fragmentShader: /* glsl */ `
     uniform sampler2D colorTexture;
+    uniform sampler2D bloomRowsTexture;
     uniform vec2 colorTextureDimensions;
     uniform float intensity;
     uniform float time;
@@ -209,21 +257,15 @@ export const thermalShader = {
 
       // ── Hot-spot bloom/bleed ────────────────────────────
       // Sample a wider area for bloom on bright spots
+      // Rows were summed by the bloomRows pass; the columns are summed here.
       float bloomSample = 0.0;
       float bloomWeight = 0.0;
       for (int y = -4; y <= 4; y++) {
-        for (int x = -4; x <= 4; x++) {
-          vec2 offset = vec2(float(x), float(y)) * texel * 3.0;
-          float sLuma = dot(texture(colorTexture, uv + offset).rgb, vec3(0.299, 0.587, 0.114));
-          float sMapped = clamp((sLuma - (0.5 - sens * 0.5)) / sens, 0.0, 1.0);
-          float sFinal = mix(sMapped, 1.0 - sMapped, isBlackHot);
-          float w = exp(-0.5 * float(x * x + y * y) / 8.0);
-          // Only bloom the "hot" pixels (bright in WHOT, dark values in BHOT...
-          // but since we already inverted, just bloom high values)
-          float hotness = smoothstep(0.6, 1.0, sFinal);
-          bloomSample += hotness * w;
-          bloomWeight += w;
-        }
+        vec2 offset = vec2(0.0, float(y)) * texel * 3.0;
+        vec2 rows = texture(bloomRowsTexture, uv + offset).rg;
+        float w = exp(-0.5 * float(y * y) / 8.0);
+        bloomSample += (rows.r + rows.g / 255.0) * w;
+        bloomWeight += w;
       }
       bloomSample /= bloomWeight;
       thermalColor += bloomSample * bloom * 0.8;
diff --git a/src/ui/visualEffects.js b/src/ui/visualEffects.js
index 9d10f0cef..6c5d3795f 100644
--- a/src/ui/visualEffects.js
+++ b/src/ui/visualEffects.js
@@ -1,4 +1,4 @@
-import { PostProcessStage } from 'cesium';
+import { PostProcessStage, PostProcessStageComposite } from 'cesium';
 import {
   bloomStrengthFromIntensity,
   clampBloomIntensity,
@@ -26,6 +26,7 @@ export class VisualEffects {
     now = () => performance.now(),
     wallNow = () => Date.now(),
     createStage = (options) => new PostProcessStage(options),
+    createComposite = (options) => new PostProcessStageComposite(options),
   }) {
     this.viewer = viewer;
     this.requestRender = requestRender;
@@ -36,6 +37,7 @@ export class VisualEffects {
     this.now = now;
     this.wallNow = wallNow;
     this.createStage = createStage;
+    this.createComposite = createComposite;
     this.stages = {};
     this.transitions = new Map();
     this.startTime = wallNow();
@@ -60,11 +62,11 @@ export class VisualEffects {
         uniforms.time = 0.0;
       for (const [name, meta] of Object.entries(shader.uniforms || {}))
         uniforms[name] = meta.default;
-      const stage = this.createStage({
-        name: `godsEyeView_${name}`,
-        fragmentShader: shader.fragmentShader,
+      const stage = this.createStyleStage(
+        `godsEyeView_${name}`,
+        shader,
         uniforms,
-      });
+      );
       stage.enabled = false;
       this.viewer.scene.postProcessStages.add(stage);
       this.stages[name] = stage;
@@ -72,6 +74,57 @@ export class VisualEffects {
     this.stageEntries = Object.entries(this.stages);
   }
 
+  /**
+   * One stage for a single-pass style. A style with `passes` becomes a
+   * composite: each pass reads the scene, the main shader reads the scene and
+   * each pass's output, and the composite answers to the style's name,
+   * `enabled` and `uniforms` as a single stage would.
+   *
+   * Cesium replaces a stage's `uniforms` object on its first frame, so the
+   * composite's uniforms and the passes' read the main stage's current object
+   * each time rather than the one it was created with.
+   */
+  createStyleStage(name, shader, uniforms) {
+    if (!shader.passes?.length)
+      return this.createStage({
+        name,
+        fragmentShader: shader.fragmentShader,
+        uniforms,
+      });
+    let main = null;
+    const shared = {};
+    for (const uniform of Object.keys(uniforms))
+      Object.defineProperty(shared, uniform, {
+        enumerable: true,
+        get: () => main.uniforms[uniform],
+        set: (value) => {
+          main.uniforms[uniform] = value;
+        },
+      });
+    const passes = shader.passes.map((pass) => {
+      const passName = `${name}_${pass.name}`;
+      uniforms[pass.texture] = passName;
+      return this.createStage({
+        name: passName,
+        fragmentShader: pass.fragmentShader,
+        uniforms: Object.fromEntries(
+          pass.uniforms.map((uniform) => [uniform, () => shared[uniform]]),
+        ),
+      });
+    });
+    main = this.createStage({
+      name: `${name}_main`,
+      fragmentShader: shader.fragmentShader,
+      uniforms,
+    });
+    return this.createComposite({
+      name,
+      stages: [...passes, main],
+      inputPreviousStageTexture: false,
+      uniforms: shared,
+    });
+  }
+
   initPostProcess(sharpenIntensity = this.sharpenIntensity) {
     if (this.stopped || this.sharpenStage) return;
     this.bloomStage = this.viewer.scene.postProcessStages.bloom;
@@ -213,16 +266,29 @@ export class VisualEffects {
           this.transitions.delete(name);
         }
       }
+      // A style with `timeHz` moves its clock in steps and asks for one frame
+      // a step; any other animated style is drawn every frame.
       let animatedStageVisible = false;
-      for (const [, stage] of this.stageEntries) {
+      let everyFrame = this.transitions.size > 0;
+      let stepped = false;
+      for (const [name, stage] of this.stageEntries) {
         if (stage.enabled && stage.uniforms.time !== undefined) {
-          stage.uniforms.time = elapsedSec;
-          if (stage.uniforms.intensity > 0.001) animatedStageVisible = true;
+          const hz = STYLES[name].timeHz;
+          const time = hz ? Math.floor(elapsedSec * hz) / hz : elapsedSec;
+          if (stage.uniforms.intensity > 0.001) {
+            animatedStageVisible = true;
+            if (!hz) everyFrame = true;
+            else if (time !== stage.uniforms.time) stepped = true;
+          }
+          stage.uniforms.time = time;
         }
       }
       const needed = this.transitions.size > 0 || animatedStageVisible;
-      if (needed) this.holdRender('style-anim');
-      else this.releaseRender('style-anim');
+      if (everyFrame) this.holdRender('style-anim');
+      else {
+        this.releaseRender('style-anim');
+        if (stepped) this.requestRender('style-anim');
+      }
       this.frameId = needed ? this.requestFrame(update) : null;
     };
     this.frameId = this.requestFrame(update);
diff --git a/src/ui/visualEffects.test.mjs b/src/ui/visualEffects.test.mjs
index 142bbbe4f..a22f5810b 100644
--- a/src/ui/visualEffects.test.mjs
+++ b/src/ui/visualEffects.test.mjs
@@ -8,7 +8,7 @@ import {
   MILITARY_DETECTION_PRESET,
 } from './visualPresets.js';
 
-function fixture() {
+function fixture(overrides = {}) {
   let time = 0;
   let next = 0;
   const frames = new Map();
@@ -52,6 +52,7 @@ function fixture() {
     now: () => time,
     wallNow: () => 10_000 + time,
     createStage: (options) => ({ ...options, enabled: true }),
+    ...overrides,
   });
   function tick(value) {
     time = value;
@@ -149,6 +150,111 @@ test('only visible animated stages keep the animation clock and render hold aliv
   f.effects.destroy();
 });
 
+test('night vision and FLIR step their clock at 15 Hz and ask for one frame a step', () => {
+  for (const name of ['surveillance', 'thermal']) {
+    const f = fixture();
+    f.effects.initStyles();
+    const stage = f.effects.stages[name];
+    f.effects.setStageIntensity(stage, 1);
+    const steps = () =>
+      f.requests.filter((reason) => reason === 'style-anim').length;
+    f.tick(1000);
+    assert.equal(stage.uniforms.time, 1);
+    assert.equal(f.holds.size, 0, 'no continuous render while idle');
+    assert.equal(steps(), 1);
+    assert.equal(f.frames.size, 1, 'the clock keeps running');
+    for (const time of [1016, 1033, 1050]) f.tick(time);
+    assert.equal(stage.uniforms.time, 1, 'the clock holds between steps');
+    assert.equal(steps(), 1, 'no frame is asked for between steps');
+    f.tick(1067);
+    assert.equal(stage.uniforms.time, 16 / 15);
+    assert.equal(steps(), 2);
+    f.tick(2000);
+    assert.equal(stage.uniforms.time, 2);
+    assert.equal(steps(), 3);
+    f.effects.setStageIntensity(stage, 0);
+    f.tick(2100);
+    assert.equal(f.frames.size, 0);
+    f.effects.destroy();
+  }
+});
+
+test('a crossfade into a stepped style is still drawn every frame', () => {
+  const f = fixture();
+  f.effects.initStyles();
+  f.effects.startTransition('thermal', 0, 1);
+  f.tick(250);
+  assert.equal(f.holds.has('style-anim'), true);
+  f.tick(500);
+  assert.equal(f.effects.stages.thermal.uniforms.intensity, 1);
+  f.tick(520);
+  assert.equal(f.holds.size, 0, 'the hold ends with the crossfade');
+  assert.equal(f.frames.size, 1);
+  f.effects.destroy();
+});
+
+test('a style with passes is one composite whose uniforms reach every pass', () => {
+  const created = [];
+  const composites = [];
+  const f = fixture({
+    createStage: (options) => {
+      const stage = { ...options, enabled: true };
+      created.push(stage);
+      return stage;
+    },
+    createComposite: (options) => {
+      const composite = {
+        ...options,
+        get enabled() {
+          return options.stages[0].enabled;
+        },
+        set enabled(value) {
+          for (const stage of options.stages) stage.enabled = value;
+        },
+      };
+      composites.push(composite);
+      return composite;
+    },
+  });
+  f.effects.initStyles();
+  assert.deepEqual(
+    composites.map((composite) => composite.name),
+    ['godsEyeView_surveillance', 'godsEyeView_thermal'],
+  );
+  assert.equal(f.stages.size, 5, 'one pipeline entry per style');
+  const composite = f.effects.stages.surveillance;
+  const [rows, main] = composite.stages;
+  assert.equal(composite.inputPreviousStageTexture, false);
+  assert.equal(rows.name, 'godsEyeView_surveillance_bloomRows');
+  assert.equal(main.uniforms.bloomRowsTexture, rows.name);
+  assert.deepEqual(Object.keys(rows.uniforms), ['gain']);
+  assert.deepEqual(Object.keys(composite.uniforms), [
+    'intensity',
+    'time',
+    'gain',
+    'bloom',
+    'scanlineStr',
+    'pixelation',
+  ]);
+  assert.equal(rows.enabled, false);
+  assert.equal(main.enabled, false);
+  // Cesium swaps a stage's uniforms object on its first frame.
+  main.uniforms = { ...main.uniforms };
+  composite.uniforms.gain = 0.9;
+  assert.equal(main.uniforms.gain, 0.9);
+  assert.equal(rows.uniforms.gain(), 0.9);
+  f.effects.setStageIntensity(composite, 1);
+  assert.equal(main.uniforms.intensity, 1);
+  assert.equal(rows.enabled, true);
+  assert.equal(main.enabled, true);
+  assert.equal(
+    created.filter((stage) => stage.name.startsWith('godsEyeView_thermal'))
+      .length,
+    2,
+  );
+  f.effects.destroy();
+});
+
 test('direct Cockpit intensity writes are reconciled before rendering', () => {
   const f = fixture();
   f.effects.initStyles();