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

AnimationLoopTemplate

The luma.gl v9 API is currently in public review.

AnimationLoopTemplate is a helper class that manages the applications render loop. provides a number of conveniences related to initialization of a Device and update of per-frame animation parameters.

It is a wrapper of the AnimationLoop class that is easier to work with in TypeScript.

Usage

import {AnimationLoopTemplate} from `@luma.gl/engine`;

Autocreates a canvas/context

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

class AppAnimationLoopTemplate extends AnimationLoopTemplate {
  clipSpaceQuad: ClipSpace;

  constructor({device) {
    // Keys in the object returned here will be available in onRender
    this.clipSpaceQuad = new ClipSpace({gl, fs: FRAGMENT_SHADER});
  }

  onFinalize() {
    this.clipSpaceQuad.destroy();
  }

  onRender({tick}) {
    // Tick is auto updated by AnimationLoopTemplate
    this.clipSpaceQuad.setUniforms({uTime: tick * 0.01});
    this.clipSpaceQuad.draw();
  }
});

new AppAnimationLoopTemplate().start();

Use a canvas in the existing DOM through its HTML id

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

Types

AnimationLoopTemplateProps

Parameter	Type	Description
device?	Device	If supplied, will render into this external context instead of creating a new one.
glOptions={} (object)		Options to create the WebGLContext with. See createGLContext.
onCreateContext?	(callback)	function without parameters that returns a WebGLRenderingContext. This callback will be called exactly once, after page load completes.
onInitialize	(callback)	if supplied, will be called once after first start() has been called, after page load completes and a context has been created.
onRender?	(callback)	Called on every animation frame.
onFinalize?	(callback)	Called once when animation is stopped. Can be used to delete objects or free any resources created during onInitialize.
onError?	(callback)	Called when an error is about to be thrown.
autoResizeViewport=true	boolean	If true, calls gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight) each frame before onRender is called. Set to false to control viewport size.
autoResizeDrawingBuffer=true	boolean	If true, checks the canvas size every frame and updates the drawing buffer size if needed.
useDevicePixels	boolean | number	Whether to use window.devicePixelRatio as a multiplier, e.g. in autoResizeDrawingBuffer etc. Refer to Experimental API section below for more use cases of this prop.

AnimationProps

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

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(props: Object)

new AnimationLoopTemplate({
  onCreateContext,
  onInitialize,
  onFinalize,
  onRender,
  autoResizeViewport,
  autoResizeDrawingBuffer
});

start([options: Object]): AnimationLoopTemplate

Restarts the animation

animationLoop.start(options)

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

stop(): AnimationLoopTemplate

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 read pixels from webgl context
loop.gl.readPixels(...)

redraw(): AnimationLoopTemplate

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

setNeedsRedraw(reason: String): AnimationLoopTemplate

animationLoop.setNeedsRedraw(reason)

• 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.
• AnimationLoopTemplate automatically sets this flag if the WebGL context's drawing buffer size changes.

setProps(props: Object): AnimationLoopTemplate

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.

attachTimeline(timeline: Timeline): void

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(): void

Detach the currently attached timeline from the animation loop.

toDataURL(): string

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()

isContextLost(): boolean

Returns the current state of the WebGL context used by the animation loop.

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).

Experimental API (useDevicePixels)

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. For additional details check device pixels document.

Remarks

• You can instantiate multiple AnimationLoopTemplate classes in parallel, rendering into the same or different WebGLRenderingContexts.

• Works both in browser and under Node.js.

• All AnimationLoopTemplate 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 when calling createGLContext.

• 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 AnimationLoopTemplate constructor.

• When running in the browser, this class uses requestAnimationFrame

• WebGL Fundamentals contains excellent information on the subtleties of the how the WebGL context's drawing buffer and the HTML canvas interact.