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Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

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If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

HTML

              
                <canvas id="canvas"></canvas>

<!-- vertex shader -->
<script id="vs" type="f">
	attribute vec2 position;
	attribute vec2 texcoord;

	uniform mat3 u_matrix;

	varying vec2 v_texcoord;

	void main() {
		 gl_Position = vec4(u_matrix * vec3(position, 1), 1);
		 v_texcoord = texcoord;
	}
</script>

<!-- fragment shader -->
<script id="fs" type="f">
	precision mediump float;

	uniform vec2 u_mouse;

	uniform sampler2D u_originalImage;
	uniform sampler2D u_mapImage;

	varying vec2 v_texcoord;

	void main() {
		 vec4 depthDistortion = texture2D(u_mapImage, v_texcoord);
		 float parallaxMult = depthDistortion.r;

		 vec2 parallax = (u_mouse) * parallaxMult;

		 vec4 original = texture2D(u_originalImage, (v_texcoord + parallax));
		 gl_FragColor = original;
	}
</script>
              
            
!

CSS

              
                body { margin: 0;}
canvas { width: 100vw; height: 100vh; display: block; }
              
            
!

JS

              
                "use strict";

function main() {
  // Get A WebGL context
  /** @type {HTMLCanvasElement} */
  const canvas = document.getElementById("canvas");
  const gl = canvas.getContext("webgl");
  if (!gl) {
    return;
  }

  let originalImage = { width: 1, height: 1 }; // replaced after loading
  const originalTexture = twgl.createTexture(gl, {
    src: "https://robindelaporte.fr/codepen/dog1.jpg", 
    crossOrigin: '',
  }, (err, texture, source) => {
    originalImage = source;
  });
  
  const mapTexture = twgl.createTexture(gl, {
    src: "https://robindelaporte.fr/codepen/dog3.jpg", crossOrigin: '',
  });
  

  // compile shaders, link program, lookup location
  const programInfo = twgl.createProgramInfo(gl, ["vs", "fs"]);

  // calls gl.createBuffer, gl.bindBuffer, gl.bufferData for a quad
  const bufferInfo = twgl.primitives.createXYQuadBufferInfo(gl);

  const mouse = [0, 0];
  document.addEventListener('mousemove', (event) => {
    mouse[0] = (event.clientX / gl.canvas.clientWidth  * 2 - 1) * -0.02;
    mouse[1] = (event.clientY / gl.canvas.clientHeight * 2 - 1) * -0.02;
  });
	
	document.addEventListener('touchmove', (event) => {
    mouse[0] = (event.touches[0].clientX / gl.canvas.clientWidth  * 2 - 1) * -0.02;
    mouse[1] = (event.touches[0].clientY / gl.canvas.clientHeight * 2 - 1) * -0.02;
  });
	
	document.addEventListener('touchend', (event) => {
    mouse[0] = 0;
    mouse[1] = 0;
  });
	
	var nMouse = [0, 0];
	var oMouse = [0, 0];
  
  requestAnimationFrame(render);
  
  function render() {
    
    twgl.resizeCanvasToDisplaySize(gl.canvas);

    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

    gl.clearColor(0, 0, 0, 0);
    gl.clear(gl.COLOR_BUFFER_BIT);

    gl.useProgram(programInfo.program);

    // calls gl.bindBuffer, gl.enableVertexAttribArray, gl.vertexAttribPointer
    twgl.setBuffersAndAttributes(gl, programInfo, bufferInfo);

    const canvasAspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
    const imageAspect = originalImage.width / originalImage.height;
    const mat = m3.scaling(imageAspect / canvasAspect, -1);
		
		nMouse[0] += (mouse[0] - nMouse[0]) * 0.05;
		nMouse[1] += (mouse[1] - nMouse[1]) * 0.05;
			
    // calls gl.activeTexture, gl.bindTexture, gl.uniformXXX
    twgl.setUniforms(programInfo, {
      u_matrix: mat,
      u_originalImage: originalTexture,
      u_mapImage: mapTexture,
      u_mouse: nMouse,
    });
		
    // calls gl.drawArrays or gl.drawElements
    twgl.drawBufferInfo(gl, bufferInfo);
    
    requestAnimationFrame(render);
  }
}

main();
              
            
!
999px

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