week02-webgl/2d/06a-displacement.html

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<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>WebGL</title>
</head>
<body>
  <canvas id="c"></canvas>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/gsap/3.5.0/gsap.min.js" integrity="sha512-JO6JyFPJupQKZf7icgZkHwuq/rAQxH7COqvEd4WdK52AtHPedwHog05T69pIelI69jVN/zZbW6TuHfH2mS8j/Q==" crossorigin="anonymous"></script>

  <script>
  {

    const createShader = (gl, type, source) => {
      const shader = gl.createShader(type);
      gl.shaderSource(shader, source);
      gl.compileShader(shader);
      const success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
      if (success) {
        return shader;
      }
      console.error(gl.getShaderInfoLog(shader));
      gl.deleteShader(shader);
    };

    const createProgram = (gl, vertexShader, fragmentShader) => {
      const program = gl.createProgram();
      gl.attachShader(program, vertexShader);
      gl.attachShader(program, fragmentShader);
      gl.linkProgram(program);
      const success = gl.getProgramParameter(program, gl.LINK_STATUS);
      if (success) {
        return program;
      }
      console.error(gl.getProgramInfoLog(program));
      gl.deleteProgram(program);
    };

    const canvas = document.querySelector('#c');
    const gl = canvas.getContext('webgl');
    const vertexShader = createShader(gl, gl.VERTEX_SHADER, `
    precision mediump float;
    
    attribute vec2 a_position;
    attribute vec2 a_texCoord;

    varying vec2 uv;
    
    void main() {     
      gl_Position = vec4(a_position, 1, 1);
      uv = a_texCoord;
    }
    `);
    const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, `
    precision mediump float;

    uniform sampler2D texture;
    uniform sampler2D disp;

    uniform float effectFactor;

    varying vec2 uv;
    
    void main() {
      vec4 disp = texture2D(disp, uv);
      vec2 distortedPosition = vec2(uv.x + disp.r*effectFactor, uv.y);
      gl_FragColor = texture2D(texture, distortedPosition);
    }
    `);
    const program = createProgram(gl, vertexShader, fragmentShader);
    const positionAttributeLocation = gl.getAttribLocation(program, "a_position");
    const positionBuffer = gl.createBuffer();
    const texCoordAttributeLocation = gl.getAttribLocation(program, "a_texCoord");
    const texCoordBuffer = gl.createBuffer();

    const effectFactorLocation = gl.getUniformLocation(program, "effectFactor");

    const properties = {
      effectFactor: 0.1
    };

    const init = async () => {
      const imgTexture = await loadImage("images/devine_selectie-087.jpg");
      // const imgDisplacement = await loadImage("images/displacement-stripes.png");
      const imgDisplacement = await loadImage("images/displacement-triangles.jpg");

      gl.useProgram(program);

      gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
      gl.bufferData(
        gl.ARRAY_BUFFER,
        new Float32Array([
            -1.0, 1.0,
            1.0, 1.0,
            -1.0, -1.0,
            -1.0, -1.0,
            1.0, 1.0,
            1.0, -1.0
        ]),
        gl.STATIC_DRAW);
      gl.enableVertexAttribArray(positionAttributeLocation);
      gl.vertexAttribPointer(positionAttributeLocation, 2, gl.FLOAT, false, 0, 0);

      gl.bindBuffer(gl.ARRAY_BUFFER, texCoordBuffer);
      gl.bufferData(
        gl.ARRAY_BUFFER,
        new Float32Array([
            0.0, 0.0,
            1.0, 0.0,
            0.0, 1.0,

            0.0, 1.0,
            1.0, 0.0,
            1.0, 1.0,
        ]),
        gl.STATIC_DRAW);
      gl.enableVertexAttribArray(texCoordAttributeLocation);
      gl.vertexAttribPointer(texCoordAttributeLocation, 2, gl.FLOAT, false, 0, 0);

      uploadImageToTexture(imgTexture, "texture", 0);
      uploadImageToTexture(imgDisplacement, "disp", 1);

      canvas.width = imgTexture.width;
      canvas.height = imgTexture.height;

      canvas.addEventListener('mouseover', () => gsap.to(properties, { duration: 1, ease: Power4.easeOut, effectFactor: 0.0}));
      canvas.addEventListener('mouseout', () => gsap.to(properties, { duration: 1, ease: Power4.easeOut, effectFactor: 0.1}));

      drawScene();
    };

    const drawScene = () => {
      gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
      gl.clearColor(0, 0, 0, 0);
      gl.clear(gl.COLOR_BUFFER_BIT);
      gl.useProgram(program);
      
      gl.uniform1f(effectFactorLocation, properties.effectFactor);

      gl.drawArrays(gl.TRIANGLES, 0, 6);

      requestAnimationFrame(drawScene);
    };

    const loadImage = (src) => {
      return new Promise((resolve, reject) => {
        const img = new Image();
        img.addEventListener("load", () => resolve(img));
        img.addEventListener("error", err => reject(err));
        img.src = src;
      });
    };

    const uploadImageToTexture = (img, uniformName, textureUnitIndex) => {
      const u_imageLoc = gl.getUniformLocation(program, uniformName);
      gl.uniform1i(u_imageLoc, textureUnitIndex);

      const texture = gl.createTexture();
      gl.activeTexture(gl.TEXTURE0 + textureUnitIndex);
      gl.bindTexture(gl.TEXTURE_2D, texture);
    
      // Set the parameters so we can render any size image.
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
    
      // Upload the image into the texture.
      gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, img);
    };

    init();
  }
  </script>
</body>
</html>