luma.gl/docs/api-reference/engine/animation-loop.md

AnimationLoop

Manages an animation loop and optionally a WebGL context and a WebGL canvas. It provides a number of features related to initialization and animation of a WebGL context.

Usage

import {AnimationLoop, ClipSpace} from '@luma.gl/engine';

const animationLoop = new AnimationLoop({
  device: luma.createDevice(...),
  override onInitialize({device}) {
    // Keys in the object returned here will be available in onRender
    this.clipSpaceQuad = new ClipSpace({device, fs: FRAGMENT_SHADER});
  }
  override onRender({tick}) {
    // Tick is autoupdated by AnimationLoop
    clipSpaceQuad.setUniforms({uTime: tick * 0.01}).draw();
  }
});

animationLoop.start();

Use a canvas in the existing DOM through its HTML id

animationLoop.start({canvas: 'my-canvas'});

Types

AnimationLoopProps

Property	Type	Default	Description
device?	Device | Promise<Device>		A Device to render into.
onInitialize?	(callback)		Called once after the first call to animationLoop.start(). Use to create GPU resources
onRender?	(callback)		- Called on every animation frame. Use to render .
onFinalize?	(callback)		- Called once when animation is stopped. Used to delete objects or free any resources created during onInitialize?
onError	(callback)		- Called when an error is about to be thrown.
autoResizeViewport?	boolean	true	If true, auto resizes GPU viewport each frame before onRender is called.
autoResizeDrawingBuffer?	boolean	true	If true, resizes the drawing buffer each frame before onRender is called.
useDevicePixels?	boolean | number		Multiplier. true uses window.devicePixelRatio as a multiplier in autoResizeDrawingBuffer etc.
stats?	Stats		A probe.gl Stats instance, Auto-created if not supplied.

AnimationProps

The onInitialize, onRender and onFinalizecallbacks will be called with an object containing the following fields:

Parameter	Type	Description
animationLoop	AnimationLoopTemplate	The calling AnimationLoopTemplate instance
device	Device	This AnimationLoopTemplate's gl context.
canvas	HTMLCanvasElement or OffscreenCanvas	The canvas associated with this context.
aspect	number	The canvas aspect ratio (width/height) to update projection matrices
width		The drawing buffer width, in "device" pixels (can be different from canvas.width).
height		The drawing buffer height, in "device" pixels (can be different from canvas.width).
useDevicePixels	boolean	Boolean indicating if canvas is utilizes full resolution of Retina/
needsRedraw	String	Redraw flag (will be automatically set if drawingBuffer resizes)
time	Number	Milliseconds since AnimationLoopTemplate was created (monotonic).
tick	Number	Counter that updates for every frame rendered (monotonic).
renderPass	RenderPass	Availabel if createFrameBuffer: true was passed to the constructor.
_mousePosition	[x, y] or null	(experimental) Current mouse position over the canvas.
_timeline	Timeline	(experimental) Timeline object tracking the animation timeline and channels.

Methods

constructor

Creates a new AnimationLoop.

new AnimationLoop(props : AnimationLoopProps)

• props - See documentation of AnimationLoopProps above.

setProps(props : Object)

animationLoop.setProps({...props})

• props.autoResizeViewport - Call gl.viewport before each call to onRender()
• props.autoResizeDrawingBuffer - Update the drawing buffer size to match the canvas size before each call to onRender()
• props.useDevicePixels - Whether to use window.devicePixelRatio as a multiplier, e.g. in autoResizeDrawingBuffer etc.

start()

Restarts the animation

animationLoop.start(options)

• options={} (object) - Options to create the WebGLContext with.

stop()

Stops the animation

animationLoop.stop()

waitForRender() : Promise

Returns a promise which resolves in the next frame after rendering and the onRender callback have completed.

const loop = await animationLoop.waitForRender()
// can now e.g. read pixels from webgl context
...

redraw()

Immediately invokes a redraw (call onRender with updated animation props). Only use if the canvas must be updated synchronously.

setNeedsRedraw()

animationLoop.setNeedsRedraw(reason: string)

• reason (String) - A human readable string giving a hint as to why redraw was needed (e.g. "geometry changed").

If set, the value will be provided as the needsRedraw field to the onRender callback.

Notes:

• onRender will be called for each animation frame regardless of whether this flag is set, and the redraw reason is automatically cleared.
• If called multiple times, the reason provided in the first call will be remembered.
• AnimationLoop automatically sets this flag if the WebGL context's drawing buffer size changes.

needsRedraw()

animationLoop.needsRedraw(): false | string

Returns the current redraw reason string, or false if no redraw was requested. Calling this method clears the flag.

attachTimeline()

attachTimeline(timeline: Timeline)

Attach an Timeline object to the animation loop. Allows time produced for animations to be paused, played, etc. See Timeline documentation for more info.

detachTimeline()

Detach the currently attached timeline from the animation loop.

toDataURL()

Returns returns a Promise that resolves to the data URL of the canvas once drawing operations are complete for the current frame. The data URL can be used as the src for an HTML image element.

animationLoop.toDataURL()

Callback Parameters

The callbacks onInitialize, onRender and onFinalize that the app supplies to the AnimationLoop, will be called with an object containing named parameters:

Frame timers

• The animation loop tracks GPU and CPU render time of each frame the in member properties cpuTime and gpuTime. If gpuTime is set to -1, then the timing for the last frame was invalid and should not be used (this rare and might occur, for example, if the GPU was throttled mid-frame).

Remarks

• You can instantiate multiple AnimationLoop classes in parallel, rendering into the same or different devices.
• Works both in browser and under Node.js.
• All AnimationLoop methods can be chained.
• Postpones context creation until the page (i.e. all HTML) has been loaded. At this time it is safe to specify canvas ids.
• The supplied callback function must return a WebGLRenderingContext or an error will be thrown.
• This callback registration function should not be called if a WebGLRenderingContext was supplied to the AnimationLoop constructor.
• useDevicePixels can accept a custom ratio (Number), instead of true or false. This allows rendering to a much smaller or higher resolutions. When using high value (usually more than device pixel ratio), it is possible it can get clamped down, this happens due to system memory limitation, in such cases a warning will be logged to the browser console.
• `onInitialize`` is called after page load completes and the passed in device promise has been resolved (the device has been created).