perf(globe): less churn in movers and lines

Review of Tasks 2–3:
- the mover store's instance checks no longer build arrays or closures
  per set() (orientation and colour checked field by field), and dirty()
  returns one reused range object;
- Cesium models get their matrix and colour through scratch objects
  (Model.modelMatrix and Model.color copy what they are given) instead
  of a new Matrix4 and Color per placement;
- a destroyed MoverSet releases its store (count 0, empty instance
  arrays, no pick ids) so a set object a layer still holds keeps no
  memory, and the Cesium parts drop their billboard, point and model
  lists;
- (with the overlay commit) the Navara line viewport is updated in
  place.

Node micro-measure, 10 000 instances set + packed per frame: 0.27-0.29
ms, about 1.7 KB per frame (0.17 B per instance), as before. Contract:
Cesium 70/70, Navara 76/76.

src/globe/cesium/movers.js

@@ -12,6 +12,8 @@ const scratchPosition = new Cesium.Cartesian3();
 const scratchColor = new Cesium.Color();
 const scratchQuaternion = new Cesium.Quaternion();
 const scratchRotation = new Cesium.Matrix3();
+// Model.modelMatrix and Model.color copy what they are given.
+const scratchModelMatrix = new Cesium.Matrix4();
 
 /** The atlas cells as canvases, by key (a DOM canvas or image source). */
 async function cropAtlasCells(atlas, keys) {
@@ -143,6 +145,9 @@ function spritePart(scene, options, store, factories, requestRender, owners) {
     },
     destroy() {
       destroyed = true;
+      billboards.length = 0;
+      shownCell.length = 0;
+      cells = null;
     },
   };
 }
@@ -180,7 +185,9 @@ function pointPart(options, store, factories, requestRender, owners) {
         }
       requestRender('movers');
     },
-    destroy() {},
+    destroy() {
+      points.length = 0;
+    },
   };
 }
 
@@ -203,13 +210,12 @@ function modelPart(options, store, factories, requestRender, owners) {
     item.modelMatrix = Cesium.Matrix4.fromRotationTranslation(
       Cesium.Matrix3.fromQuaternion(scratchQuaternion, scratchRotation),
       readPosition(store, index),
-      new Cesium.Matrix4(),
+      scratchModelMatrix,
     );
     item.scale = store.scales[index];
     item.show = index < store.count && store.shows[index] === 1;
     item.id = store.pickIds[index];
-    if (model.colorBlend)
+    if (model.colorBlend) item.color = readColor(store, index);
-      item.color = Cesium.Color.clone(readColor(store, index));
   };
   const ensure = (index) => {
     if (models[index] || loading[index]) return;
@@ -258,6 +264,8 @@ function modelPart(options, store, factories, requestRender, owners) {
     },
     destroy() {
       destroyed = true;
+      models.length = 0;
+      loading.length = 0;
     },
   };
 }

src/globe/movers.js

@@ -150,17 +150,18 @@ export function normalizeMoverSetOptions(options) {
 export function createMoverStore(options) {
   const { capacity, cellKeys, kind } = options;
   const cellIndex = new Map(cellKeys.map((key, index) => [key, index]));
-  const positions = new Float64Array(capacity * 3);
+  let positions = new Float64Array(capacity * 3);
-  const orientations = new Float64Array(capacity * 4);
+  let orientations = new Float64Array(capacity * 4);
-  const colors = new Float32Array(capacity * 4).fill(1);
+  let colors = new Float32Array(capacity * 4).fill(1);
-  const rotations = new Float32Array(capacity);
+  let rotations = new Float32Array(capacity);
-  const scales = new Float32Array(capacity).fill(1);
+  let scales = new Float32Array(capacity).fill(1);
-  const cells = new Uint16Array(capacity);
+  let cells = new Uint16Array(capacity);
-  const shows = new Uint8Array(capacity).fill(1);
+  let shows = new Uint8Array(capacity).fill(1);
-  const pickIds = new Array(capacity);
+  let pickIds = new Array(capacity);
   for (let index = 0; index < capacity; index++)
     orientations[index * 4 + 3] = 1;
   let count = 0;
+  const range = { from: 0, to: 0 };
   let dirtyFrom = Infinity;
   let dirtyTo = -Infinity;
   const touch = (from, to) => {
@@ -189,7 +190,10 @@ export function createMoverStore(options) {
       orientation !== undefined &&
       !(
         isObject(orientation) &&
-        ['x', 'y', 'z', 'w'].every((axis) => isFiniteNumber(orientation[axis]))
+        isFiniteNumber(orientation.x) &&
+        isFiniteNumber(orientation.y) &&
+        isFiniteNumber(orientation.z) &&
+        isFiniteNumber(orientation.w)
       )
     )
       throw new TypeError('Mover orientation must be a quaternion');
@@ -198,7 +202,10 @@ export function createMoverStore(options) {
       !(
         (Array.isArray(color) || ArrayBuffer.isView(color)) &&
         color.length === 4 &&
-        Array.prototype.every.call(color, isFiniteNumber)
+        isFiniteNumber(color[0]) &&
+        isFiniteNumber(color[1]) &&
+        isFiniteNumber(color[2]) &&
+        isFiniteNumber(color[3])
       )
     )
       throw new TypeError('Mover color must be [r, g, b, a]');
@@ -256,9 +263,40 @@ export function createMoverStore(options) {
       count = next;
     },
     positionsView: () => positions.subarray(0, count * 3),
+    /**
+     * Drops the instance arrays (a destroyed set): the count goes to 0 and
+     * the arrays to empty ones, so a set object still held keeps no memory.
+     */
+    release() {
+      count = 0;
+      positions = new Float64Array(0);
+      orientations = new Float64Array(0);
+      colors = new Float32Array(0);
+      rotations = new Float32Array(0);
+      scales = new Float32Array(0);
+      cells = new Uint16Array(0);
+      shows = new Uint8Array(0);
+      pickIds = [];
+      Object.assign(this, {
+        positions,
+        orientations,
+        colors,
+        rotations,
+        scales,
+        cells,
+        shows,
+        pickIds,
+      });
+      this.clean();
+    },
     /** Indices changed since clean(), as [from, to), or null. */
-    dirty: () =>
+    /** The changed range (one object, reused: read it at once), or null. */
-      dirtyFrom === Infinity ? null : { from: dirtyFrom, to: dirtyTo },
+    dirty() {
+      if (dirtyFrom === Infinity) return null;
+      range.from = dirtyFrom;
+      range.to = dirtyTo;
+      return range;
+    },
     clean() {
       dirtyFrom = Infinity;
       dirtyTo = -Infinity;
@@ -296,6 +334,7 @@ export function createMoverSet(store, { commit, destroy }) {
       if (destroyed) return;
       destroyed = true;
       destroy();
+      store.release?.();
     },
     isDestroyed: () => destroyed,
   };

src/globe/movers.test.mjs

@@ -170,7 +170,7 @@ test('the set facade forwards to the store and an engine commit, once destroyed
   );
   const calls = [];
   const set = createMoverSet(store, {
-    commit: () => calls.push(['commit', store.dirty()]),
+    commit: () => calls.push(['commit', { ...store.dirty() }]),
     destroy: () => calls.push(['destroy']),
   });
   set.set(0, { position: { x: 1, y: 2, z: 3 } });
@@ -187,3 +187,23 @@ test('the set facade forwards to the store and an engine commit, once destroyed
   assert.throws(() => set.set(0, {}), /destroyed/);
   assert.throws(() => set.commit(), /destroyed/);
 });
+
+test('a destroyed set releases its instance arrays', () => {
+  const store = createMoverStore(
+    normalizeMoverSetOptions({
+      id: 'r',
+      kind: 'point',
+      capacity: 1000,
+      point: { sizePx: 2 },
+    }),
+  );
+  const set = createMoverSet(store, { commit() {}, destroy() {} });
+  set.set(0, { position: { x: 1, y: 2, z: 3 }, pickId: 'p' });
+  set.setCount(1);
+  set.destroy();
+  assert.equal(store.count, 0);
+  assert.equal(store.positions.length, 0);
+  assert.equal(store.pickIds.length, 0);
+  assert.equal(set.positionsView().length, 0);
+  assert.equal(store.dirty(), null);
+});