When ReactJS meets PixiJS

🟰

I'm J.D. Nicholls 👋

- Open Source Contributor 👨‍💻

- Game developer (Hobby) 🎮

- Developer who loves UX 💫

- Chocolate lover 🍫

- Founding Full-Stack Engineer 👷

AT

Why PixiJS? 🤔

WebGL/Canvas brought about an era of rich visualization on the web since Adobe Flash.

PixiJS is one of the most popular rendering engines build on WebGL with fallback support to Canvas.

PixiJS

But What's WebGL? 🤓

WebGL is a JavaScript-rendering API that offers high-performance 2D and 3D interactive graphics capability and GPU acceleration

However, WebGL has a steeper learning curve, so several frameworks have been built upon the API to ease the complications of working with it directly.

WebGL Example

// https://www.shadertoy.com/view/MdXSzS
// The Big Bang - just a small explosion somewhere in a massive Galaxy of Universes.

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
	vec2 uv = (fragCoord.xy / iResolution.xy) - .5;
	float t = iTime * .1 + ((.25 + .05 * sin(iTime * .1))/(length(uv.xy) + .07)) * 2.2;
	float si = sin(t);
	float co = cos(t);
	mat2 ma = mat2(co, si, -si, co);

	float v1, v2, v3;
	v1 = v2 = v3 = 0.0;
	
	float s = 0.0;
	for (int i = 0; i < 90; i++)
	{
		vec3 p = s * vec3(uv, 0.0);
		p.xy *= ma;
		p += vec3(.22, .3, s - 1.5 - sin(iTime * .13) * .1);
		for (int i = 0; i < 8; i++)	p = abs(p) / dot(p,p) - 0.659;
		v1 += dot(p,p) * .0015 * (1.8 + sin(length(uv.xy * 13.0) + .5  - iTime * .2));
		v2 += dot(p,p) * .0013 * (1.5 + sin(length(uv.xy * 14.5) + 1.2 - iTime * .3));
		v3 += length(p.xy*10.) * .0003;
		s  += .035;
	}
	
	float len = length(uv);
	v1 *= smoothstep(.7, .0, len);
	v2 *= smoothstep(.5, .0, len);
	v3 *= smoothstep(.9, .0, len);
	
	vec3 col = vec3( v3 * (1.5 + sin(iTime * .2) * .4),
					(v1 + v3) * .3,
					 v2) + smoothstep(0.2, .0, len) * .85 + smoothstep(.0, .6, v3) * .3;

	fragColor=vec4(min(pow(abs(col), vec3(1.2)), 1.0), 1.0);
}

WebGPU; the future is here! 🔮

Now WebGPU propels web computations and graphics into a new era, providing a more efficient and robust API. Soon, it will be the go-to method for rendering most GPU-powered content on the web.

WebGPU is the successor to WebGL, providing better compatibility with modern GPUs, support for general-purpose GPU computations, faster operations, and access to more advanced GPU features.

Use PIXI with React 🧑‍🚀

npm install pixi.js @pixi/react --save

Let's build this together 👷

Stories App

const App: React.FC = () => {
  // raf allows to automatically renders the stage on request animation frame.
  return (
    <div className="flex-1 flex items-center justify-center">
      <Stage
        raf={true}
        options={{
          backgroundColor: 0xffffff,
          autoDensity: true,
          antialias: true,
        }}
      >
      </Stage>
    </div>
  );
};

export default App;

Create a custom Component

The Stage in PixiJS is the root container that orchestrates the scene, holding and managing all visual elements within an application.

const App: React.FC = () => {
  // useState can detect if the component is unmounted (Dialogs)
  const [parentEl, setParentEl] = useState<HTMLDivElement>();
  const { size: parentSize, resize } = useElementSize<HTMLDivElement>({
    el: parentEl,
  });

  return (
    <div
      ref={(ref) => setParentEl(ref || undefined)}
      className="flex-1 flex items-center justify-center"
    >
      <Stage
        raf={true}
        options={{
          backgroundColor: 0xffffff,
          resizeTo: parentEl,
          autoDensity: true,
          antialias: true,
        }}
      >
      </Stage>
    </div>
  );
};

export default App;

Let's resize our Component

Let's re-learn React;

Why useState instead of useRef ❓

  • Refs Do Not Trigger Re-renders; ref is useful for accessing a DOM element to read its dimensions but does not inherently communicate changes in the referenced element or component to React's rendering system.
  • Reactivity to Size Changes; Using a useState and custom hook combination integrates seamlessly with React's declarative nature, enabling components to automatically adjust to size changes in a more efficient and React-centric manner (useful in responsive designs where the canvas size might need to adjust dynamically to layout changes)

Why not supporting both? 🤪

The Hard Way is the Easy Way; coding.

Ok, just do it!

export type ElementProps<T> = {
  ref?: MutableRefObject<T>;
  el?: T;
};

// A hook for getting the HTML element using refs or React state
export const useElement = <T extends HTMLElement>(props: ElementProps<T>) => {
  // get the Element using refs
  const ref = useCombinedRefs<T>(props.ref);
  // or get the element using React state
  const el = useMemo(() => props?.el || ref?.current, [ref, props.el]);

  // Update the ref when the element changes (When getting the element using React state)
  useEffect(() => {
    if (props?.el && ref) {
      ref.current = props?.el;
    }
  }, [ref, props?.el]);

  return {
    el,
    ref,
  };
};

Now getting the size of a HTML element is "easy" 😅

import useResizeObserver from "@react-hook/resize-observer";
import { useElement } from "./useElement";

export type ElementSizeProps<T> = {
  ref?: MutableRefObject<T>;
  el?: T;
};

/**
 * A hook for measuring the size of HTML elements including when they change
 * @returns the size of the HTML element
 */
export const useElementSize = <T extends HTMLElement>(
  props: ElementSizeProps<T>
) => {
  // Get the element
  const { el, ref } = useElement(props)
  // The size of the element
  const [size, setSize] = useState<DOMRect>(
    () => el?.getBoundingClientRect() || new DOMRect()
  );
  // Use ResizeObserver to resize the element when it changes (Performance)
  useResizeObserver(el!, (entry) => setSize(entry.contentRect));

  return { size, ref, el };
};
const App: React.FC = () => {
  // ...
  const initializeApp = (app: Application) => {
    setApp(app);
    resize();
    app.stage.eventMode = "static";
    app.stage.hitArea = app.screen;
  };
  return (
    // ...
      <Stage
        // ...
        width={CANVAS_WIDTH}
        height={CANVAS_HEIGHT}
        onMount={initializeApp}
      >
      </Stage>
    // ...
  );
};

Responsive PixiJS App is here! 🏁

const App: React.FC = ({ photo }) => {
  // Custom hook to calculate new dimensions with a 9:16 aspect ratio
  const { width, height, centerX, centerY } = useStageDimensions({
    app,
    parentWidth: parentSize?.width,
    parentHeight: parentSize?.height,
  });

  return (
    <Stage>
      // Stretching to fit the given dimension
      {!!photo && (
        <Sprite
          image={photo}
          width={width}
          height={height}
          anchor={0}
          position={[centerX, centerY]}
        />
      )}
    </Stage>
  );
};

Add a our first responsive Sprite! 📦

Only render the sprite when there's a photo! 🫡

const App: React.FC = ({ photo }) => {
  // Custom hook to calculate new dimensions with a 9:16 aspect ratio
  const { width, height, centerX, centerY, ratio } = useStageDimensions({
    app,
    parentWidth: parentSize?.width,
    parentHeight: parentSize?.height,
  });

  return (
    <Stage>
      // The image keeps the aspect ratio
      {!!photo && (
        <Sprite
          image={photo}
          scale={ratio}
          anchor={0.5}
          x={CANVAS_WIDTH / 2}
          y={CANVAS_HEIGHT / 2}
        />
      )}
    </Stage>
  );
};

Keeps a 9:16 aspect ratio 🖼️

Add draggable stickers 🐈

const App: React.FC = ({ stickers }) => {
  // Custom hook to calculate new dimensions with a 9:16 aspect ratio
  const { width, height, centerX, centerY, ratio } = useStageDimensions({
    app,
    parentWidth: parentSize?.width,
    parentHeight: parentSize?.height,
  });

  return (
    <Stage>
      {stickers?.map((sticker, index) => (
        <DraggableContainer
          key={`${sticker}_${index}`}
          width={CANVAS_WIDTH}
          height={CANVAS_HEIGHT}
          scale={ratio}
          x={centerX}
          y={centerY}
        >
          <ImageSprite
            app={app}
            imageSrc={sticker}
            anchor={0.5}
            x={CANVAS_WIDTH / 2}
            y={CANVAS_HEIGHT / 2}
          />
        </DraggableContainer>
      ))}
    </Stage>
  );
};

Use Web Share API  

export const shareOrDownloadImage = async (
  filename: string,
  imageBlob: Blob
) => {
  if (navigator.canShare) {
    const file = new File([imageBlob], filename, { type: imageBlob.type });
    const filesArray = [file];
    if (navigator.canShare({ files: filesArray })) {
      try {
        return await navigator.share({
          files: filesArray,
        });
      } catch (error) {
        console.error(`shareOrDownloadImage(${error})`);
        downloadImage(filename, imageBlob);
      }
    }
  }
  downloadImage(filename, imageBlob);
};

With the Web Share API, we can now create applications that allow users to share data as they would from a native application

Download the image as a fallback  

const downloadImage = (filename: string, imageBlob: Blob) => {
  const anchorElement = document.createElement("a");
  const fileUrl = URL.createObjectURL(imageBlob);
  anchorElement.href = fileUrl;
  anchorElement.download = filename;
  anchorElement.click();
  anchorElement.remove();
  URL.revokeObjectURL(fileUrl);
};

Share Canvas Image with PixiJS 🅿️ 

export const renderAndShareCanvasImage = async (
  app: Application,
  filename: string,
  imageWidth: number,
  imageHeight: number,
  centerX: number,
  centerY: number,
  format = "image/png",
  extension = "png"
) => {
  const renderTexture = RenderTexture.create({
    width: imageWidth,
    height: imageHeight,
    resolution: window.devicePixelRatio || 1,
  });
  const transformMatrix = new Matrix().translate(-centerX, -centerY);

  app.renderer.render(app.stage, {
    renderTexture,
    transform: transformMatrix,
  });

  const base64 = await app.renderer.extract.base64(renderTexture, format, 1);
  const blob = base64StringToBlob(
    base64.replace(`data:${format};base64,`, ""),
    format
  );
  await shareOrDownloadImage(`${filename}.${extension}`, blob);
};

Resources 🔗

Pixi Packages


- PixiJS Essentials Kit: https://github.com/ShukantPal/pixi-essentials

PixiJS & ReactJS

By Juan David Nicholls

PixiJS & ReactJS

A brief presentation about mixing Canvas/WebGL/WebGPU with React using PixiJS for creating amazing web experiences! <3

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