refactor to fps tracker class

packages/engine/Source/Core/FpsTracker.js

@@ -0,0 +1,40 @@
+import destroyObject from "../Core/destroyObject.js";
+import getTimestamp from "../Core/getTimestamp.js";
+
+/**
+ * @private
+ */
+function FpsTracker(options) {
+  this._timeStamps = [];
+}
+
+/**
+ * Calculates average fps based on timeStamps of recently rendered frames
+ */
+FpsTracker.prototype.getAverageFps = function () {
+  if (this._timeStamps.length !== 10) {
+    return;
+  }
+  const elapsedTime = (this._timeStamps[0] - this._timeStamps[9]) / 9;
+  const fps = 1 / (elapsedTime / 1000);
+  return fps;
+};
+
+/**
+ * Adds the timestamp for the current frame to the queue
+ */
+FpsTracker.prototype.updateFrameTimeStamp = function () {
+  const time = getTimestamp();
+  this._timeStamps.unshift(time);
+  if (this._timeStamps.length > 10) {
+    this._timeStamps.pop();
+  }
+};
+
+/**
+ * Destroys the WebGL resources held by this object.
+ */
+FpsTracker.prototype.destroy = function () {
+  return destroyObject(this);
+};
+export default FpsTracker;

packages/engine/Source/Scene/Scene.js

@@ -77,7 +77,7 @@ import View from "./View.js";
 import DebugInspector from "./DebugInspector.js";
 import VoxelCell from "./VoxelCell.js";
 import VoxelPrimitive from "./VoxelPrimitive.js";
-import getTimestamp from "../Core/getTimestamp.js";
+import FpsTracker from "../Core/FpsTracker.js";
 
 const requestRenderAfterFrame = function (scene) {
   return function () {
@@ -163,6 +163,7 @@ function Scene(options) {
   this._frameState.scene3DOnly = defaultValue(options.scene3DOnly, false);
   this._removeCreditContainer = !hasCreditContainer;
   this._creditContainer = creditContainer;
+  this._fpsTracker = new FpsTracker();
 
   this._canvas = canvas;
   this._context = context;
@@ -749,7 +750,6 @@ function Scene(options) {
 
   // Give frameState, camera, and screen space camera controller initial state before rendering
   updateFrameNumber(this, 0.0, JulianDate.now());
-  this.updateFrameTimeStamp();
   this.updateFrameState();
   this.initializeFrame();
 }
@@ -1919,18 +1919,6 @@ function updateFrameNumber(scene, frameNumber, time) {
   frameState.time = JulianDate.clone(time, frameState.time);
 }
 
-/**
- * @private
- */
-Scene.prototype.updateFrameTimeStamp = function () {
-  const frameState = this._frameState;
-  const time = getTimestamp();
-  frameState.timeStamps.unshift(time);
-  if (frameState.timeStamps.length > 10) {
-    frameState.timeStamps.pop();
-  }
-};
-
 /**
  * @private
  */
@@ -4110,7 +4098,7 @@ Scene.prototype.render = function (time) {
       1.0
     );
     updateFrameNumber(this, frameNumber, time);
-    this.updateFrameTimeStamp();
+    this._fpsTracker.updateFrameTimeStamp();
     frameState.newFrame = true;
   }
 

packages/engine/Source/Scene/ScreenSpaceCameraController.js

@@ -574,12 +574,9 @@ function handleZoom(
 
   const minDistance = distanceMeasure - minHeight;
 
-  const timeStamps = object._scene.frameState?.timeStamps;
   let fpsMultiplier = 1;
-  if (timeStamps?.length === 10) {
-    const elapsedTime = (timeStamps[0] - timeStamps[9]) / 9;
-    const fps = 1 / (elapsedTime / 1000);
-    // target refresh rate of 30hz
+  const fps = object._scene._fpsTracker.getAverageFps();
+  if (fps) {
     fpsMultiplier = 30 / fps;
   }