The Scene Optimizer

How To Use SceneOptimizer

Rendering a scene in a browser is great because you can reach many different users and hardware configurations. However, the main caveat is that you may encounter very low-end devices.

The SceneOptimizer tool is designed to help you reach a specific framerate by gracefully degrading rendering quality at runtime.

Basic usage

To start using the SceneOptimizer, you can create a new BABYLON.SceneOptimizer instance. The SceneOptimizer constructor requires the current scene and a BABYLON.SceneOptimizerOptions object (we will come back to it later).

import { HardwareScalingOptimization, SceneOptimizer, SceneOptimizerOptions } from "@babylonjs/core/Misc/sceneOptimizer";
var options = new SceneOptimizerOptions();
options.addOptimization(new HardwareScalingOptimization(0, 1));
// Optimizer
var optimizer = new SceneOptimizer(scene, options);

When creating the SceneOptimizer, you can provide the following parameters:

A BABYLON.Scene which will define the scene to work on
A BABYLON.SceneOptimizerOptions which will define the options to use with the SceneOptimizer
A boolean which will define if priorities must be generated and not read from SceneOptimization property (true by default)
A boolean which will define if the optimizer will run in improvement mode (see below) (false by default)

The SceneOptimizer object allows you to set several properties:

optimizations: This property contains the list of current optimizations
targetFrameRate: This property defines the target frame rate to reach (60 by default)
trackerDuration: This property defines the interval between two checks (2000ms by default)
currentFrameRate: This property (read-only) gets the current frame rate checked by the SceneOptimizer
currentPriorityLevel: This property (read-only) gets the current priority level (0 at start)
onSuccessObservable: This property defines an observable called when the optimizer reaches the target frame rate
onNewOptimizationAppliedObservable: This property defines an observable called when the optimizer enables an optimization
onFailureObservable: This property defines an observable called when the optimizer is not able to reach the target frame rate

It also provides several functions:

start(): used to start the overall optimization process
stop(): used to stop the current process
reset(): used to restore the current priority level to 0
dispose(): used to release all resources

Helper

You can also use a static helper that will create everything you need in one line: BABYLON.SceneOptimizer.OptimizeAsync(). You can call this function when you want to optimize your scene. The simplest call is the following:

import { SceneOptimizer } from "@babylonjs/core/Misc/sceneOptimizer";
SceneOptimizer.OptimizeAsync(scene),

You have to provide at least a scene. That previous line of code is actually equivalent to this:

import { SceneOptimizer, SceneOptimizerOptions } from "@babylonjs/core/Misc/sceneOptimizer";
SceneOptimizer.OptimizeAsync(scene, SceneOptimizerOptions.ModerateDegradationAllowed(), function () {
    // On success
}, function () {
    // FPS target not reached
});

As you can see, you can provide success/fail callbacks and a set of options. Please note that the BABYLON.SceneOptimizer.OptimizeAsync() function returns a SceneOptimizer object which is created with autoGeneratePriorities set to false.

Options

A set of options contains a list of optimizations to apply in a specific order. As soon as the target FPS is reached, the SceneOptimizer stops. There are different layers (or passes) that are applied one after another. The SceneOptimizer pauses between each layer to ensure a stable FPS and to measure it. Create a BABYLON.SceneOptimizerOptions like this:

import { SceneOptimizerOptions } from "@babylonjs/core/Misc/sceneOptimizer";
// With a target framerate of 50fps and a check|rate of 500ms
let optimizerOptions = new SceneOptimizerOptions(50, 500);

Here are the properties available on a BABYLON.SceneOptimizerOptions instance:

targetFrameRate: a number defining the FPS you want to achieve (60 by default)
optimizations: an array of BABYLON.SceneOptimization objects.
trackerDuration: time in milliseconds between passes (2000 by default)

By default, there are 3 sets available:

import { SceneOptimizerOptions } from "@babylonjs/core/Misc/sceneOptimizer";
SceneOptimizerOptions.LowDegradationAllowed();
SceneOptimizerOptions.ModerateDegradationAllowed();
SceneOptimizerOptions.HighDegradationAllowed();

All these sets return a BABYLON.SceneOptimizerOptions object configured with progressive degradations.

Based on these optimizations, the basic sets are configured like this:

BABYLON.SceneOptimizerOptions.LowDegradationAllowed():
- Level 0: MergeMeshesOptimization, ShadowsOptimization and LensFlaresOptimization
- Level 1: PostProcessesOptimization and ParticlesOptimization
- Level 2: TextureOptimization(2, 1024)
BABYLON.SceneOptimizerOptions.ModerateDegradationAllowed():
- Level 0: MergeMeshesOptimization, ShadowsOptimization and LensFlaresOptimization
- Level 1: PostProcessesOptimization and ParticlesOptimization
- Level 2: TextureOptimization(2, 512)
- Level 3: RenderTargetsOptimization
- Level 4: HardwareScalingOptimization(4, 2)
BABYLON.SceneOptimizerOptions.HighDegradationAllowed():
- Level 0: MergeMeshesOptimization, ShadowsOptimization and LensFlaresOptimization
- Level 1: PostProcessesOptimization and ParticlesOptimization
- Level 2: TextureOptimization(2, 256)
- Level 3: RenderTargetsOptimization
- Level 4: HardwareScalingOptimization(4, 4)

The Built-in Optimizations.

The priority of an optimization is used by the SceneOptimizer to form a queue of optimizations. When performing optimizations, the SceneOptimizer starts with optimizations with lower priority, then continues to optimizations with higher priorities:

BABYLON.MergeMeshesOptimization(priority): This optimization will merge meshes with the same material.
BABYLON.TextureOptimization(priority, maximumSize): This optimization tries to reduce the size of render textures.
BABYLON.HardwareScalingOptimization(priority, maximumScale): This optimization increments or decrements the value of hardware scaling. This is a really aggressive optimization that could really help if you are GPU-bound.
BABYLON.ShadowsOptimization(priority): This optimization disables shadows (It will turn them on if the optimizer is in improvement mode (see below)).
BABYLON.PostProcessesOptimization(priority): This optimization disables post-processes (It will turn them on if the optimizer is in improvement mode (see below)).
BABYLON.LensFlaresOptimization(priority): This optimization disables lens flares (It will turn them on if the optimizer is in improvement mode (see below)).
BABYLON.ParticlesOptimization(priority): This optimization disables particles (It will turn them on if the optimizer is in improvement mode (see below)).
BABYLON.RenderTargetsOptimization(priority): This optimization disables render targets (It will turn them on if the optimizer is in improvement mode (see below)).
BABYLON.CustomOptimization(priority): This optimization will call two callbacks when required:
onApply(scene, optimizer): A custom callback used to apply custom optimizations. It must return true if all optimizations were applied
onGetDescription(): This callback must return a string describing the action of the optimization

Custom Optimizations.

You can create your own optimizations by extending the class BABYLON.CustomOptimization. The new class must provide two functions, onApply and onGetDescription. Every instance takes a priority as its only argument, and it must be a number. For example:

import { CustomOptimization } from "@babylonjs/core/Misc/sceneOptimizer";
class MyCustomOptimization extends CustomOptimization {
    constructor(priority) {
        super(priority);
    }
    onApply() {
        // Some optimizing code
    }
    onGetDescription() {
        // A desription of your optimization
        return "I make framerate go prrrr!";
    }
}
;
options.addOptimization(new MyCustomOptimization(2));

A much simpler shorthand is available, using the addCustomOptimization method, on a BABYLON.SceneOptimizerOptions() instance:

// Using shorthand syntax, fn(onApply, onGetDescrition, priority)
options.addCustomOptimization(function () {
	// Some optimizing code
}, function () {
    return "Making optimizations...";
}, 0.6);

Advanced Usage

You can create your own set of options with the following code (please note that if autoGeneratePriorities is true, you don't need to define the priority value):

import { HardwareScalingOptimization, LensFlaresOptimization, ParticlesOptimization, PostProcessesOptimization, RenderTargetsOptimization, SceneOptimizerOptions, ShadowsOptimization, TextureOptimization } from "@babylonjs/core/Misc/sceneOptimizer";
var result = new SceneOptimizerOptions(60, 2000);
var priority = 0;
result.optimizations.push(new ShadowsOptimization(priority));
result.optimizations.push(new LensFlaresOptimization(priority));
// Next priority
priority++;
result.optimizations.push(new PostProcessesOptimization(priority));
result.optimizations.push(new ParticlesOptimization(priority));
// Next priority
priority++;
result.optimizations.push(new TextureOptimization(priority, 256));
// Next priority
priority++;
result.optimizations.push(new RenderTargetsOptimization(priority));
// Next priority
priority++;
result.optimizations.push(new HardwareScalingOptimization(priority, 4));
return result;

Improvement Mode

When created in improvement mode (4th parameter of the constructor), the SceneOptimizer object will run all optimizations while the current FPS is above the target frame rate. So, for instance, if the target FPS is 60, the optimizer will execute all optimizations in its list while the FPS remains at 60. It is a good tool for providing rendering improvements to a given scene. Please note that when in improvement mode, the optimizations will adapt their behavior automatically (for instance, the ShadowsOptimization will turn shadows on instead of off).

Demos

Scene Optimizer Example CustomOptimization Example