Add a utility to adjust rendering quality based on rendering performance.

samples/o3djs/performance.js

Index: samples/o3djs/performance.js
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+/*
+ * Copyright 2009, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+
+/**
+ * @fileoverview This file contains a utility that helps adjust rendering
+ * quality [or any other setting, really] based on rendering performance.
+ *
+ */
+
+o3djs.provide('o3djs.performance');
+
+/**
+ * Creates a utility that monitors performance [in terms of FPS] and helps to
+ * adjust the rendered scene accordingly.
+ * @param {number} targetFPSMin the minimum acceptable frame rate; if we're
+ * under this, try to decrease quality to improve performance.
+ * @param {number} targetFPSMax if we're over this, try to increase quality.
+ * @param {!function(): void} increaseQuality a function to increase
+ *     quality because we're rendering at high-enough FPS to afford it.
+ * @param {!function(): void} decreaseQuality a function to decrease
+ *     quality to try to raise our rendering speed.
+ * @param {!o3djs.performance.PerformanceMonitor.Options} opt_options Options.
+ * @return {!o3djs.performance.PerformanceMonitor} The created
+ *     PerformanceMonitor.
+ */
+o3djs.performance.createPerformanceMonitor = function(
+    targetFPSMin, targetFPSMax, increaseQuality, decreaseQuality, opt_options) {
+  return new o3djs.performance.PerformanceMonitor(targetFPSMin, targetFPSMax,
+      increaseQuality, decreaseQuality, opt_options);
+}
+
+/**
+ * A class that monitors performance [in terms of FPS] and helps to adjust the
+ * rendered scene accordingly.
+ * @constructor
+ * @param {number} targetFPSMin the minimum acceptable frame rate; if we're
+ * under this, try to decrease quality to improve performance.
+ * @param {number} targetFPSMax if we're over this, try to increase quality.
+ * @param {function(): void} increaseQuality a function to increase
+ *     quality/lower FPS.
+ * @param {function(): void} decreaseQuality a function to decrease
+ *     quality/raise FPS.
+ * @param {!o3djs.performance.PerformanceMonitor.Options} opt_options Options.
+ */
+o3djs.performance.PerformanceMonitor = function(
+    targetFPSMin, targetFPSMax, increaseQuality, decreaseQuality, opt_options) {
+  opt_options = opt_options || {};
+
+  /**
+   * A function to increase quality/lower FPS.
+   * @type {function(): void} 
+   */
+  this.increaseQuality = increaseQuality;
+
+  /**
+   * A function to decrease quality/raise FPS.
+   * @type {function(): void} 
+   */
+  this.decreaseQuality = decreaseQuality;
+
+  /**
+   * The mean time taken per frame so far, in seconds.  This is only valid once
+   * we've collected at least minSamples samples.
+   * @type {number} 
+   */
+  this.meanFrameTime = 0;
+
+  /**
+   * The number of samples we've collected so far, when that number is less than
+   * or equal to this.damping.  After that point, we no longer update
+   * this.sampleCount, so it will clip at this.damping.
+   *
+   * @type {number} 
+   */
+  this.sampleCount = 0;
+
+  /**
+   * The minimum number of samples to collect before trying to adjust quality.
+   *
+   * @type {number} 
+   */
+  this.minSamples = opt_options.opt_minSamples || 60;
+
+  /**
+   * A number that controls the rate at which the effects of any given sample
+   * fade away.  Higher is slower, but also means that each individual sample
+   * counts for less at its most-influential.  Damping defaults to 120; anywhere
+   * between 60 and 600 are probably reasonable values, depending on your needs,
+   * but the number must be no less than minSamples.
+   *
+   * @type {number} 
+   */
+  this.damping = opt_options.opt_damping || 120;
+
+  /**
+   * The minimum number of samples to take in between adjustments, to cut down
+   * on overshoot.  It defaults to 2 * minSamples.
+   *
+   * @type {number} 
+   */
+  this.delayCycles = opt_options.opt_delayCycles || 2 * this.minSamples;
+
+  this.targetFrameTimeMax_ = 1 / targetFPSMin;
+  this.targetFrameTimeMin_ = 1 / targetFPSMax;
+  this.scaleInput_ = 1 / this.minSamples;
+  this.scaleMean_ = 1;
+  this.delayCyclesLeft_ = 0;
+  if (this.damping < this.minSamples) {
+    throw Error('Damping must be at least minSamples.');
+  }
+}
+
+/**
+ * Options for the PerformanceMonitor.
+ *
+ * opt_minSamples is the minimum number of samples to take before making any
+ * performance adjustments.
+ * opt_damping is a number that controls the rate at which the effects of any
+ * given sample fade away.  Higher is slower, but also means that each
+ * individual sample counts for less at its most-influential.  Damping
+ * defaults to 120; anywhere between 60 and 600 are probably reasonable values,
+ * depending on your needs, but the number must be no less than minSamples.
+ * opt_delayCycles is the minimum number of samples to take in between
+ * adjustments, to cut down on overshoot.  It defaults to 2 * opt_minSamples.
+ *
+ * @type {{
+ *   opt_minSamples: number,
+ *   opt_damping: number,
+ *   opt_delayCycles, number
+ * }}
+ */
+o3djs.performance.PerformanceMonitor.Options = goog.typedef;
+
+/**
+ * Call this once per frame with the elapsed time since the last call, and it
+ * will attempt to adjust your rendering quality as needed.
+ *
+ * @param {number} seconds the elapsed time since the last frame was rendered,
+ * in seconds.
+ */
+o3djs.performance.PerformanceMonitor.prototype.onRender = function(seconds) {
+  var test = true;
+  if (this.sampleCount < this.damping) {
+    if (this.sampleCount >= this.minSamples) {
+      this.scaleInput_ = 1 / (this.sampleCount + 1); 
+      this.scaleMean_ = this.sampleCount * this.scaleInput_; 
+    } else {
+      test = false;
+    }
+    this.sampleCount += 1;
+  }
+  this.meanFrameTime = this.meanFrameTime * this.scaleMean_ +
+      seconds * this.scaleInput_;
+  if (this.delayCyclesLeft_ > 0) {
+    this.delayCyclesLeft_ -= 1;
+  } else if (test) {
+    if (this.meanFrameTime < this.targetFrameTimeMin_) {
+      this.increaseQuality();
+      this.delayCyclesLeft_ = this.delayCycles;
+    } else if (this.meanFrameTime > this.targetFrameTimeMax_) {
+      this.decreaseQuality();
+      this.delayCyclesLeft_ = this.delayCycles;
+    }
+  }
+}
+