examples/test_custom_shader3.html from spritejs/spritejs

examples/test_custom_shader3.html
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<!DOCTYPE html>
<html lang="en">
<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>Document</title>
  <script src="/js/spritejs.js"></script>
  <style>
    #container {
      position: absolute;
      width: 600px;
      height: 600px;
    }
  </style>
</head>
<body>
  <div id="container"></div>
  <script>
    const vertex = `
      attribute vec3 a_vertexPosition;
      attribute vec4 a_color;
      varying vec4 vColor;
      uniform mat3 viewMatrix;
      uniform mat3 projectionMatrix;

      void main() {
        gl_PointSize = 1.0;
        vec3 pos = projectionMatrix * viewMatrix * vec3(a_vertexPosition.xy, 1.0);
        gl_Position = vec4(pos.xy, 1.0, 1.0);
        vColor = a_color;
      }
    `;

    const fragment = `
      precision mediump float;
      uniform vec4 u_color;
      uniform vec2 u_resolution;
      varying vec4 vColor;

      void main() {
        vec2 st = gl_FragCoord.xy / u_resolution;
        float d = (st.x - st.y) / sqrt(2.0);
        d = fract(d * 50.0);
        d = 1.0 - abs(d);
        d = smoothstep(0.3, 0.4, d) - smoothstep(0.8, 0.9, d);
        gl_FragColor = d * vColor;
      }
    `;

    const container = document.getElementById('container');
    const scene = new spritejs.Scene({
      container,
      width: 600,
      height: 600,
    });

    const fglayer = scene.layer('fglayer');
    const program = fglayer.renderer.createProgram({vertex, fragment});
    
    const s = new spritejs.Ellipse();
    s.attr({
      radius: [100, 50],
      pos: [300, 300],
      fillColor: 'blue',
    });
    s.setProgram(program);
    fglayer.append(s);
  </script>
</body>
</html>