bojidar-bg/raymarching.html

## raymarching.html
<!DOCTYPE html>
<!-- Thanks to Inigo Quillez (http://iquilezles.org) for many of the functions in the shader code. -->
<!-- Thanks to MDN for being awesome. -->
<!-- Thanks to WebGLFundamentals (https://webglfundamentals.org) for their framebuffer tutorial. -->
<!-- Thanks to gl-matrix.js for the matrix library, and Stats.js for the FPS counter. -->
<html>
  <head>
    <meta charset="utf-8">
    <title>Raymarcher</title>
    <style media="screen">
      html, body {
        margin: 0;
        padding: 0;
        overflow: hidden;
      }
    </style>
  </head>
  <body>
    <canvas></canvas>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/gl-matrix/2.7.1/gl-matrix-min.js" integrity="sha256-+09xst+d1zIS41eAvRDCXOf0MH993E4cS40hKBIJj8Q=" crossorigin="anonymous"></script>
    <script src="https://cdn.rawgit.com/mrdoob/stats.js/r16/src/Stats.js"></script>
    <script type="text/vnd.glsl-shader" id="copyShader">
      varying highp vec2 pos;
      [vertex]
      attribute vec4 vertexPosition;
      void main() {
        gl_Position = vertexPosition;
        pos = vertexPosition.xy;
      }

      [fragment]
      uniform sampler2D depthSoFar;

      void main() {
        gl_FragColor = texture2D(depthSoFar, (pos + vec2(1.0)) / 2.0) * vec4(1.0, 1.0, 1.0, 1.0);
      }
    </script>
    <script type="text/vnd.glsl-shader" id="scene">
      uniform mediump float time;

      mediump float sphereShape(vec3 p, float s)
      {
        return length(p) - s;
      }

      mediump float boxShape(vec3 p, vec3 b)
      {
        mediump vec3 d = abs(p) - b;
        return min(max(d.x,max(d.y,d.z)),0.0) + length(max(d,0.0));
      }

      mediump float crossShape(vec3 p, vec3 b)
      {
        return min(boxShape(p.xyz,vec3(1000.0,b.yz)),min(boxShape(p.yzx,vec3(b.x,1000.0,b.z)),boxShape(p.zxy,vec3(b.xy,1000.0))));
      }

      mediump float smin( float a, float b, float k )
      {
        mediump float h = clamp( 0.5+0.5*(b-a)/k, 0.0, 1.0 );
        return mix( b, a, h ) - k*h*(1.0-h);
      }

      mediump float scene(vec3 p)
      {
        mediump vec3 rep = vec3(7.0, 7.0, 7.0);
        mediump vec3 p_rep = mod(p, rep) - rep * 0.5;
        mediump vec3 p_c = p * 2.0 + vec3(0.67, 0.76, 0.23) * time;
        return sphereShape(p_rep, (sin(p_c.x) * sin(p_c.y) * sin(p_c.z) + 3.0) * 0.5);
      }

      mediump vec3 sceneNormal(vec3 p, float eps)
      {
        mediump float o = scene(p);
        return normalize(vec3(
          o - scene(p + vec3(eps, 0, 0)),
          o - scene(p + vec3(0, eps, 0)),
          o - scene(p + vec3(0, 0, eps))
        ));
        // return normalize(vec3(
        //   scene(p - vec3(eps, 0, 0)) - scene(p + vec3(eps, 0, 0)),
        //   scene(p - vec3(eps, 0, 0)) - scene(p + vec3(0, eps, 0)),
        //   scene(p - vec3(eps, 0, 0)) - scene(p + vec3(0, 0, eps))
        // ));
      }
    </script>
    <script type="text/vnd.glsl-shader" id="depthShader">
      varying highp vec2 pos;
      [vertex]
      attribute vec4 vertexPosition;
      void main() {
        gl_Position = vertexPosition;
        pos = vertexPosition.xy;
      }

      [fragment include:#scene]
      uniform mediump mat4 projectionMatrix;
      uniform mediump mat4 modelViewMatrix;
      uniform mediump vec2 pixelSize;
      uniform mediump float far;
      uniform sampler2D depthSoFar;

      highp vec3 computeRayDirection(vec2 screenPosition) {
        return normalize(vec3(screenPosition.x / projectionMatrix[0].x, screenPosition.y / projectionMatrix[1].y, 1));
      }

      void main() {
        mediump vec3 rayDirection = computeRayDirection(pos);
        mediump vec3 nextRayDirection = computeRayDirection(pos + pixelSize * 3.0);
        mediump float raySlope = distance(rayDirection, nextRayDirection);
        mediump vec3 rayOrigin = projectionMatrix[3].xyz;

        mediump vec4 soFar = texture2D(depthSoFar, (pos + vec2(1.0)) / 2.0);
        mediump float depth = soFar.x * far;

        if (depth > far) {
          gl_FragColor = vec4(soFar.x, soFar.x, soFar.z / 4.0, 1.0);
          return;
        }

        mediump float distance = 0.0;
        int iterations = 1;
        depth -= abs(scene((modelViewMatrix * vec4(rayOrigin + depth * rayDirection, 1.0)).xyz));
        for (int i = 0; i < 64; i++) {
          distance = scene((modelViewMatrix * vec4(rayOrigin + depth * rayDirection, 1.0)).xyz);
          if (distance < raySlope * depth || depth > far) {
            break;
          }
          depth += distance * 0.7;
          iterations += 1;
        }

        gl_FragColor = vec4(depth / far, soFar.x, soFar.z / 4.0 + float(iterations) / 64.0, 1.0);
      }
    </script>
    <script type="text/vnd.glsl-shader" id="shadingShader">
      varying highp vec2 pos;
      [vertex]
      attribute vec4 vertexPosition;
      void main() {
        gl_Position = vertexPosition;
        pos = vertexPosition.xy;
      }

      [fragment include:#scene]
      uniform mediump mat4 projectionMatrix;
      uniform mediump mat4 modelViewMatrix;
      uniform mediump float far;
      uniform sampler2D depthSoFar;

      void main() {
        mediump vec3 rayDirection = normalize(vec3(pos.x / projectionMatrix[0].x, pos.y / projectionMatrix[1].y, 1));
        mediump vec3 rayOrigin = projectionMatrix[3].xyz;

        mediump vec4 soFar = texture2D(depthSoFar, (pos + vec2(1.0)) / 2.0);
        mediump float depth = soFar.x * far;

        mediump vec3 normal = sceneNormal((modelViewMatrix * vec4(rayOrigin + depth * rayDirection, 1.0)).xyz, 0.01);

        mediump vec3 light1Color = vec3(1.0, 1.0, 0.9) * 0.8;
        mediump vec3 light1Direction = normalize(vec3(0.0, -1.0, 1.0));
        mediump vec3 light2Color = vec3(1.0, 1.0, 1.0) * 0.3;
        mediump vec3 light2Direction = normalize(vec3(1.0, 1.0, 1.0));
        mediump vec3 light3Color = vec3(0.8, 0.8, 1.0) * 0.3;
        mediump vec3 light3Direction = normalize(vec3(0.0, 1.0, 1.0));

        gl_FragColor = mix(
          vec4(
            light1Color * clamp(dot(normal, light1Direction), 0.0, 1.0) +
            light2Color * clamp(dot(normal, light2Direction), 0.0, 1.0) +
            light3Color * clamp(dot(normal, light3Direction), 0.0, 1.0), 1.0),
          vec4(0.0, 0.0, 0.0, 1.0),
          pow(depth / far, 2.0)
        );
        // gl_FragColor = vec4(0.0, 0.0, soFar.z, 1.0);
        // gl_FragColor = vec4((soFar.x - soFar.y), 0.0, 0.0, soFar.w);
      }
    </script>
    <script type="text/javascript">
      var stats = Stats();
      stats.showPanel(0); // 0: fps, 1: ms, 2: mb, 3+: custom
      document.body.appendChild(stats.dom);
      var canvas = document.querySelector('canvas');
      var gl = canvas.getContext('experimental-webgl') || canvas.getContext('webgl2') || canvas.getContext('webgl');

      if (!gl) {
        alert('WebGL is unsupported on your browser!');
        throw new Error('WebGL is not supported!');
      }

      gl.cbf = gl.getExtension('WEBGL_color_buffer_float') || gl.getExtension('EXT_color_buffer_float');
      gl.tf = gl.getExtension('OES_texture_float');

      var depthProgram = loadProgram('#depthShader', ['vertexPosition'], ['projectionMatrix', 'modelViewMatrix', 'depthSoFar', 'far', 'time', 'pixelSize']);
      var shadingProgram = loadProgram('#shadingShader', ['vertexPosition'], ['projectionMatrix', 'modelViewMatrix', 'depthSoFar', 'far', 'time']);
      var copyProgram = loadProgram('#copyShader', ['vertexPosition'], ['depthSoFar']);

      var projectionMatrix = mat4.create();

      var modelViewMatrix = mat4.create();
      mat4.rotate(modelViewMatrix, modelViewMatrix, 22 * Math.PI / 180, [0.8, -1.0, 0.0]);
      mat4.translate(modelViewMatrix, modelViewMatrix, [0.0, -0.0, -0.0]);
      var rectCornersBuffer = gl.createBuffer();

      gl.bindBuffer(gl.ARRAY_BUFFER, rectCornersBuffer);
      gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
        -1.0, +1.0, +0.0, +1.0,
        +1.0, +1.0, +0.0, +1.0,
        -1.0, -1.0, +0.0, +1.0,
        +1.0, -1.0, +0.0, +1.0,
      ]), gl.STATIC_DRAW);

      var blackTexture = gl.createTexture();
      gl.bindTexture(gl.TEXTURE_2D, blackTexture);
      {
        let level = 0;
        let internalFormat = gl.RGB;
        let width = 1;
        let height = 1;
        let border = 0;
        let srcFormat = gl.RGB;
        let srcType = gl.UNSIGNED_BYTE;
        let pixel = new Uint8Array([0, 0, 0]);
        gl.texImage2D(
          gl.TEXTURE_2D, level, internalFormat,
          width, height, border, srcFormat, srcType,
          pixel
        );
      }

      var framebuffers = [];

      resize();
      window.addEventListener('resize', resize);
      render(performance.now());

      function resize() {
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;

        mat4.perspective(
          projectionMatrix,
          45 * Math.PI / 180, // fov
          canvas.clientWidth / canvas.clientHeight, // aspect
          0.1, // near
          100 // far
        );
        mat4.translate(projectionMatrix, projectionMatrix, [0.0, -0.0, 5.0]);

        for (let framebuffer of framebuffers) {
          gl.deleteFramebuffer(framebuffer);
        }
        framebuffers = [];

        function createFramebuffer(width, height) {
          let framebufferTexture = gl.createTexture();
          gl.bindTexture(gl.TEXTURE_2D, framebufferTexture);

          let internalFormat = gl.RGBA;
          let border = 0;
          let format = gl.RGBA;
          let type = gl.tf ? gl.FLOAT : gl.UNSIGNED_BYTE;
          gl.texImage2D(
            gl.TEXTURE_2D, 0, internalFormat,
            width, height, border,
            format, type, null
          );

          gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
          gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
          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);

          let framebuffer = gl.createFramebuffer();
          gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);

          framebuffer.texture = framebufferTexture;
          framebuffer.width = width;
          framebuffer.height = height;

          gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, framebufferTexture, 0);

          gl.bindTexture(gl.TEXTURE_2D, null);
          gl.bindFramebuffer(gl.FRAMEBUFFER, null);

          framebuffers.push(framebuffer);
        }
        for (let size = 16; size < canvas.width; size *= 2) {
          createFramebuffer(size, Math.ceil(size * canvas.height / canvas.width));
        }

        createFramebuffer(canvas.width, canvas.height);
        // createFramebuffer(canvas.width, canvas.height);
        // createFramebuffer(canvas.width, canvas.height);
      }

      function render(time) {
        stats.begin();
        gl.useProgram(depthProgram);

        gl.bindBuffer(gl.ARRAY_BUFFER, rectCornersBuffer);
        gl.vertexAttribPointer(depthProgram.vertexPosition, 4, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray(depthProgram.vertexPosition);

        gl.uniformMatrix4fv(depthProgram.projectionMatrix, false, projectionMatrix);
        gl.uniformMatrix4fv(depthProgram.modelViewMatrix, false, modelViewMatrix);
        gl.uniform1f(depthProgram.far, 100.0);
        gl.uniform1f(depthProgram.time, time / 1000.0);
        gl.uniform1i(depthProgram.depthSoFar, 0);

        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_2D, blackTexture);

        for (let framebuffer of framebuffers) {
          gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);

          gl.uniform2f(depthProgram.pixelSize, 1.00 / framebuffer.width, 1.00 / framebuffer.height);
          gl.viewport(0, 0, framebuffer.width, framebuffer.height);

          gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);

          gl.bindTexture(gl.TEXTURE_2D, framebuffer.texture);
        }

        gl.bindFramebuffer(gl.FRAMEBUFFER, null);
        gl.viewport(0, 0, canvas.width, canvas.height);

        gl.useProgram(shadingProgram);

        gl.bindBuffer(gl.ARRAY_BUFFER, rectCornersBuffer);
        gl.vertexAttribPointer(shadingProgram.vertexPosition, 4, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray(shadingProgram.vertexPosition);

        gl.uniformMatrix4fv(shadingProgram.projectionMatrix, false, projectionMatrix);
        gl.uniformMatrix4fv(shadingProgram.modelViewMatrix, false, modelViewMatrix);
        gl.uniform1f(shadingProgram.far, 100.0);
        gl.uniform1f(shadingProgram.time, time / 1000.0);
        gl.uniform1i(shadingProgram.depthSoFar, 0);

        gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);

        // gl.useProgram(copyProgram);
        // gl.bindBuffer(gl.ARRAY_BUFFER, rectCornersBuffer);
        // gl.vertexAttribPointer(copyProgram.vertexPosition, 4, gl.FLOAT, false, 0, 0);
        // gl.enableVertexAttribArray(copyProgram.vertexPosition);
        // gl.bindTexture(gl.TEXTURE_2D, framebuffers[7].texture);
        // gl.uniform1i(copyProgram.depthSoFar, 0);
        // gl.bindFramebuffer(gl.FRAMEBUFFER, null);
        // gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);

        stats.end();

        requestAnimationFrame(render);
      }

      function loadProgram(selector, attributes, uniforms) {
        var programText = document.querySelector(selector).innerHTML;
        var programParts = programText.split(/\n\s+\[(.+?)\]/);

        const shaderProgram = gl.createProgram();

        for (let i = 1; i < programParts.length; i += 2) {
          var headersParts = programParts[i].split(' ');
          var name = headersParts[0];
          var source = programParts[0] + programParts[i+1];

          for (let j = 1; j < headersParts.length; j += 2) {
            let m;
            if (m = headersParts[j].match(/include:(.+)/)) {
              source = document.querySelector(m[1]).innerHTML + source;
            } else {
              console.error('Unrecognized directive: ' + headersParts[j]);
            }
          }

          var shader = gl.createShader(gl[name.toUpperCase() + '_SHADER']);
          gl.shaderSource(shader, source);
          gl.compileShader(shader);
          if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            console.error('An error occurred compiling the ' + name + ' shader: ' + gl.getShaderInfoLog(shader));
            let lineN = 0;
            console.log(source.replace(/\n/g, (x) => `\n[${++lineN}]`));
            gl.deleteShader(shader);
          }
          gl.attachShader(shaderProgram, shader);
        }

        gl.linkProgram(shaderProgram);

        for (let attribute of attributes) {
          shaderProgram[attribute] = gl.getAttribLocation(shaderProgram, attribute)
        }
        for (let uniform of uniforms) {
          shaderProgram[uniform] = gl.getUniformLocation(shaderProgram, uniform)
        }

        return shaderProgram;
      }
    </script>
  </body>
</html>
	<!DOCTYPE html>
	<!-- Thanks to Inigo Quillez (http://iquilezles.org) for many of the functions in the shader code. -->
	<!-- Thanks to MDN for being awesome. -->
	<!-- Thanks to WebGLFundamentals (https://webglfundamentals.org) for their framebuffer tutorial. -->
	<!-- Thanks to gl-matrix.js for the matrix library, and Stats.js for the FPS counter. -->
	<html>
	<head>
	<meta charset="utf-8">
	<title>Raymarcher</title>
	<style media="screen">
	html, body {
	margin: 0;
	padding: 0;
	overflow: hidden;
	}
	</style>
	</head>
	<body>
	<canvas></canvas>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/gl-matrix/2.7.1/gl-matrix-min.js" integrity="sha256-+09xst+d1zIS41eAvRDCXOf0MH993E4cS40hKBIJj8Q=" crossorigin="anonymous"></script>
	<script src="https://cdn.rawgit.com/mrdoob/stats.js/r16/src/Stats.js"></script>
	<script type="text/vnd.glsl-shader" id="copyShader">
	varying highp vec2 pos;
	[vertex]
	attribute vec4 vertexPosition;
	void main() {
	gl_Position = vertexPosition;
	pos = vertexPosition.xy;
	}

	[fragment]
	uniform sampler2D depthSoFar;

	void main() {
	gl_FragColor = texture2D(depthSoFar, (pos + vec2(1.0)) / 2.0) * vec4(1.0, 1.0, 1.0, 1.0);
	}
	</script>
	<script type="text/vnd.glsl-shader" id="scene">
	uniform mediump float time;

	mediump float sphereShape(vec3 p, float s)
	{
	return length(p) - s;
	}

	mediump float boxShape(vec3 p, vec3 b)
	{
	mediump vec3 d = abs(p) - b;
	return min(max(d.x,max(d.y,d.z)),0.0) + length(max(d,0.0));
	}

	mediump float crossShape(vec3 p, vec3 b)
	{
	return min(boxShape(p.xyz,vec3(1000.0,b.yz)),min(boxShape(p.yzx,vec3(b.x,1000.0,b.z)),boxShape(p.zxy,vec3(b.xy,1000.0))));
	}

	mediump float smin( float a, float b, float k )
	{
	mediump float h = clamp( 0.5+0.5*(b-a)/k, 0.0, 1.0 );
	return mix( b, a, h ) - kh(1.0-h);
	}

	mediump float scene(vec3 p)
	{
	mediump vec3 rep = vec3(7.0, 7.0, 7.0);
	mediump vec3 p_rep = mod(p, rep) - rep * 0.5;
	mediump vec3 p_c = p * 2.0 + vec3(0.67, 0.76, 0.23) * time;
	return sphereShape(p_rep, (sin(p_c.x) * sin(p_c.y) * sin(p_c.z) + 3.0) * 0.5);
	}

	mediump vec3 sceneNormal(vec3 p, float eps)
	{
	mediump float o = scene(p);
	return normalize(vec3(
	o - scene(p + vec3(eps, 0, 0)),
	o - scene(p + vec3(0, eps, 0)),
	o - scene(p + vec3(0, 0, eps))
	));
	// return normalize(vec3(
	// scene(p - vec3(eps, 0, 0)) - scene(p + vec3(eps, 0, 0)),
	// scene(p - vec3(eps, 0, 0)) - scene(p + vec3(0, eps, 0)),
	// scene(p - vec3(eps, 0, 0)) - scene(p + vec3(0, 0, eps))
	// ));
	}
	</script>
	<script type="text/vnd.glsl-shader" id="depthShader">
	varying highp vec2 pos;
	[vertex]
	attribute vec4 vertexPosition;
	void main() {
	gl_Position = vertexPosition;
	pos = vertexPosition.xy;
	}

	[fragment include:#scene]
	uniform mediump mat4 projectionMatrix;
	uniform mediump mat4 modelViewMatrix;
	uniform mediump vec2 pixelSize;
	uniform mediump float far;
	uniform sampler2D depthSoFar;

	highp vec3 computeRayDirection(vec2 screenPosition) {
	return normalize(vec3(screenPosition.x / projectionMatrix[0].x, screenPosition.y / projectionMatrix[1].y, 1));
	}

	void main() {
	mediump vec3 rayDirection = computeRayDirection(pos);
	mediump vec3 nextRayDirection = computeRayDirection(pos + pixelSize * 3.0);
	mediump float raySlope = distance(rayDirection, nextRayDirection);
	mediump vec3 rayOrigin = projectionMatrix[3].xyz;

	mediump vec4 soFar = texture2D(depthSoFar, (pos + vec2(1.0)) / 2.0);
	mediump float depth = soFar.x * far;

	if (depth > far) {
	gl_FragColor = vec4(soFar.x, soFar.x, soFar.z / 4.0, 1.0);
	return;
	}

	mediump float distance = 0.0;
	int iterations = 1;
	depth -= abs(scene((modelViewMatrix * vec4(rayOrigin + depth * rayDirection, 1.0)).xyz));
	for (int i = 0; i < 64; i++) {
	distance = scene((modelViewMatrix * vec4(rayOrigin + depth * rayDirection, 1.0)).xyz);
	if (distance < raySlope * depth \|\| depth > far) {
	break;
	}
	depth += distance * 0.7;
	iterations += 1;
	}

	gl_FragColor = vec4(depth / far, soFar.x, soFar.z / 4.0 + float(iterations) / 64.0, 1.0);
	}
	</script>
	<script type="text/vnd.glsl-shader" id="shadingShader">
	varying highp vec2 pos;
	[vertex]
	attribute vec4 vertexPosition;
	void main() {
	gl_Position = vertexPosition;
	pos = vertexPosition.xy;
	}

	[fragment include:#scene]
	uniform mediump mat4 projectionMatrix;
	uniform mediump mat4 modelViewMatrix;
	uniform mediump float far;
	uniform sampler2D depthSoFar;

	void main() {
	mediump vec3 rayDirection = normalize(vec3(pos.x / projectionMatrix[0].x, pos.y / projectionMatrix[1].y, 1));
	mediump vec3 rayOrigin = projectionMatrix[3].xyz;

	mediump vec4 soFar = texture2D(depthSoFar, (pos + vec2(1.0)) / 2.0);
	mediump float depth = soFar.x * far;

	mediump vec3 normal = sceneNormal((modelViewMatrix * vec4(rayOrigin + depth * rayDirection, 1.0)).xyz, 0.01);

	mediump vec3 light1Color = vec3(1.0, 1.0, 0.9) * 0.8;
	mediump vec3 light1Direction = normalize(vec3(0.0, -1.0, 1.0));
	mediump vec3 light2Color = vec3(1.0, 1.0, 1.0) * 0.3;
	mediump vec3 light2Direction = normalize(vec3(1.0, 1.0, 1.0));
	mediump vec3 light3Color = vec3(0.8, 0.8, 1.0) * 0.3;
	mediump vec3 light3Direction = normalize(vec3(0.0, 1.0, 1.0));

	gl_FragColor = mix(
	vec4(
	light1Color * clamp(dot(normal, light1Direction), 0.0, 1.0) +
	light2Color * clamp(dot(normal, light2Direction), 0.0, 1.0) +
	light3Color * clamp(dot(normal, light3Direction), 0.0, 1.0), 1.0),
	vec4(0.0, 0.0, 0.0, 1.0),
	pow(depth / far, 2.0)
	);
	// gl_FragColor = vec4(0.0, 0.0, soFar.z, 1.0);
	// gl_FragColor = vec4((soFar.x - soFar.y), 0.0, 0.0, soFar.w);
	}
	</script>
	<script type="text/javascript">
	var stats = Stats();
	stats.showPanel(0); // 0: fps, 1: ms, 2: mb, 3+: custom
	document.body.appendChild(stats.dom);
	var canvas = document.querySelector('canvas');
	var gl = canvas.getContext('experimental-webgl') \|\| canvas.getContext('webgl2') \|\| canvas.getContext('webgl');

	if (!gl) {
	alert('WebGL is unsupported on your browser!');
	throw new Error('WebGL is not supported!');
	}

	gl.cbf = gl.getExtension('WEBGL_color_buffer_float') \|\| gl.getExtension('EXT_color_buffer_float');
	gl.tf = gl.getExtension('OES_texture_float');

	var depthProgram = loadProgram('#depthShader', ['vertexPosition'], ['projectionMatrix', 'modelViewMatrix', 'depthSoFar', 'far', 'time', 'pixelSize']);
	var shadingProgram = loadProgram('#shadingShader', ['vertexPosition'], ['projectionMatrix', 'modelViewMatrix', 'depthSoFar', 'far', 'time']);
	var copyProgram = loadProgram('#copyShader', ['vertexPosition'], ['depthSoFar']);

	var projectionMatrix = mat4.create();

	var modelViewMatrix = mat4.create();
	mat4.rotate(modelViewMatrix, modelViewMatrix, 22 * Math.PI / 180, [0.8, -1.0, 0.0]);
	mat4.translate(modelViewMatrix, modelViewMatrix, [0.0, -0.0, -0.0]);
	var rectCornersBuffer = gl.createBuffer();

	gl.bindBuffer(gl.ARRAY_BUFFER, rectCornersBuffer);
	gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
	-1.0, +1.0, +0.0, +1.0,
	+1.0, +1.0, +0.0, +1.0,
	-1.0, -1.0, +0.0, +1.0,
	+1.0, -1.0, +0.0, +1.0,
	]), gl.STATIC_DRAW);

	var blackTexture = gl.createTexture();
	gl.bindTexture(gl.TEXTURE_2D, blackTexture);
	{
	let level = 0;
	let internalFormat = gl.RGB;
	let width = 1;
	let height = 1;
	let border = 0;
	let srcFormat = gl.RGB;
	let srcType = gl.UNSIGNED_BYTE;
	let pixel = new Uint8Array([0, 0, 0]);
	gl.texImage2D(
	gl.TEXTURE_2D, level, internalFormat,
	width, height, border, srcFormat, srcType,
	pixel
	);
	}

	var framebuffers = [];

	resize();
	window.addEventListener('resize', resize);
	render(performance.now());

	function resize() {
	canvas.width = window.innerWidth;
	canvas.height = window.innerHeight;

	mat4.perspective(
	projectionMatrix,
	45 * Math.PI / 180, // fov
	canvas.clientWidth / canvas.clientHeight, // aspect
	0.1, // near
	100 // far
	);
	mat4.translate(projectionMatrix, projectionMatrix, [0.0, -0.0, 5.0]);

	for (let framebuffer of framebuffers) {
	gl.deleteFramebuffer(framebuffer);
	}
	framebuffers = [];

	function createFramebuffer(width, height) {
	let framebufferTexture = gl.createTexture();
	gl.bindTexture(gl.TEXTURE_2D, framebufferTexture);

	let internalFormat = gl.RGBA;
	let border = 0;
	let format = gl.RGBA;
	let type = gl.tf ? gl.FLOAT : gl.UNSIGNED_BYTE;
	gl.texImage2D(
	gl.TEXTURE_2D, 0, internalFormat,
	width, height, border,
	format, type, null
	);

	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
	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);

	let framebuffer = gl.createFramebuffer();
	gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);

	framebuffer.texture = framebufferTexture;
	framebuffer.width = width;
	framebuffer.height = height;

	gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, framebufferTexture, 0);

	gl.bindTexture(gl.TEXTURE_2D, null);
	gl.bindFramebuffer(gl.FRAMEBUFFER, null);

	framebuffers.push(framebuffer);
	}
	for (let size = 16; size < canvas.width; size *= 2) {
	createFramebuffer(size, Math.ceil(size * canvas.height / canvas.width));
	}

	createFramebuffer(canvas.width, canvas.height);
	// createFramebuffer(canvas.width, canvas.height);
	// createFramebuffer(canvas.width, canvas.height);
	}

	function render(time) {
	stats.begin();
	gl.useProgram(depthProgram);

	gl.bindBuffer(gl.ARRAY_BUFFER, rectCornersBuffer);
	gl.vertexAttribPointer(depthProgram.vertexPosition, 4, gl.FLOAT, false, 0, 0);
	gl.enableVertexAttribArray(depthProgram.vertexPosition);

	gl.uniformMatrix4fv(depthProgram.projectionMatrix, false, projectionMatrix);
	gl.uniformMatrix4fv(depthProgram.modelViewMatrix, false, modelViewMatrix);
	gl.uniform1f(depthProgram.far, 100.0);
	gl.uniform1f(depthProgram.time, time / 1000.0);
	gl.uniform1i(depthProgram.depthSoFar, 0);

	gl.activeTexture(gl.TEXTURE0);
	gl.bindTexture(gl.TEXTURE_2D, blackTexture);

	for (let framebuffer of framebuffers) {
	gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);

	gl.uniform2f(depthProgram.pixelSize, 1.00 / framebuffer.width, 1.00 / framebuffer.height);
	gl.viewport(0, 0, framebuffer.width, framebuffer.height);

	gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);

	gl.bindTexture(gl.TEXTURE_2D, framebuffer.texture);
	}

	gl.bindFramebuffer(gl.FRAMEBUFFER, null);
	gl.viewport(0, 0, canvas.width, canvas.height);

	gl.useProgram(shadingProgram);

	gl.bindBuffer(gl.ARRAY_BUFFER, rectCornersBuffer);
	gl.vertexAttribPointer(shadingProgram.vertexPosition, 4, gl.FLOAT, false, 0, 0);
	gl.enableVertexAttribArray(shadingProgram.vertexPosition);

	gl.uniformMatrix4fv(shadingProgram.projectionMatrix, false, projectionMatrix);
	gl.uniformMatrix4fv(shadingProgram.modelViewMatrix, false, modelViewMatrix);
	gl.uniform1f(shadingProgram.far, 100.0);
	gl.uniform1f(shadingProgram.time, time / 1000.0);
	gl.uniform1i(shadingProgram.depthSoFar, 0);

	gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);

	// gl.useProgram(copyProgram);
	// gl.bindBuffer(gl.ARRAY_BUFFER, rectCornersBuffer);
	// gl.vertexAttribPointer(copyProgram.vertexPosition, 4, gl.FLOAT, false, 0, 0);
	// gl.enableVertexAttribArray(copyProgram.vertexPosition);
	// gl.bindTexture(gl.TEXTURE_2D, framebuffers[7].texture);
	// gl.uniform1i(copyProgram.depthSoFar, 0);
	// gl.bindFramebuffer(gl.FRAMEBUFFER, null);
	// gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);

	stats.end();

	requestAnimationFrame(render);
	}

	function loadProgram(selector, attributes, uniforms) {
	var programText = document.querySelector(selector).innerHTML;
	var programParts = programText.split(/\n\s+\[(.+?)\]/);

	const shaderProgram = gl.createProgram();

	for (let i = 1; i < programParts.length; i += 2) {
	var headersParts = programParts[i].split(' ');
	var name = headersParts[0];
	var source = programParts[0] + programParts[i+1];

	for (let j = 1; j < headersParts.length; j += 2) {
	let m;
	if (m = headersParts[j].match(/include:(.+)/)) {
	source = document.querySelector(m[1]).innerHTML + source;
	} else {
	console.error('Unrecognized directive: ' + headersParts[j]);
	}
	}

	var shader = gl.createShader(gl[name.toUpperCase() + '_SHADER']);
	gl.shaderSource(shader, source);
	gl.compileShader(shader);
	if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
	console.error('An error occurred compiling the ' + name + ' shader: ' + gl.getShaderInfoLog(shader));
	let lineN = 0;
	console.log(source.replace(/\n/g, (x) => `\n[${++lineN}]`));
	gl.deleteShader(shader);
	}
	gl.attachShader(shaderProgram, shader);
	}

	gl.linkProgram(shaderProgram);

	for (let attribute of attributes) {
	shaderProgram[attribute] = gl.getAttribLocation(shaderProgram, attribute)
	}
	for (let uniform of uniforms) {
	shaderProgram[uniform] = gl.getUniformLocation(shaderProgram, uniform)
	}

	return shaderProgram;
	}
	</script>
	</body>
	</html>