index.js

/**
 * Credit is given to the following people for their work:
 * https://github.com/gfxfundamentals/webgl2-fundamentals/graphs/contributors
 * This is a modified version of the code from this repository:
 * https://webgl2fundamentals.org/webgl/lessons/webgl-shadertoy.html
 * Many thanks to the authors for their hard work.
 */

function main() {
  // Get A WebGL context
  /** @type {HTMLCanvasElement} */
  const canvas = document.querySelector("#canvas");
  const gl = canvas.getContext("webgl2");
  if (!gl) {
    return;
  }

  const vs = `#version 300 es
     // an attribute is an input (in) to a vertex shader.
     // It will receive data from a buffer
     in vec4 a_position;

     // all shaders have a main function
     void main() {

       // gl_Position is a special variable a vertex shader
       // is responsible for setting
       gl_Position = a_position;
     }
   `;

  const fs = `#version 300 es
   precision highp float;

   uniform vec2 iResolution;
   uniform vec2 iMouse;
   uniform float iTime;

   void mainImage( out vec4 fragColor, in vec2 fragCoord )
   {

    vec2 uv = (fragCoord.xy-.5*iResolution.xy) / iResolution.y;
    vec2 st = vec2(atan(uv.x, uv.y), length(uv)*0.8);
    uv = vec2 (st.x/6.2831+.5, st.y);
    float x = uv.x*300.-0.5*iTime*0.9;
    float m = min(fract(x), fract(1.-x));
    float c = smoothstep(0.8, 1., m*1.8+0.5-uv.y);

    fragColor = vec4(c);
   }

   out vec4 outColor;

   void main() {
     mainImage(outColor, gl_FragCoord.xy);
   }
   `;

  // setup GLSL program
  const program = webglUtils.createProgramFromSources(gl, [vs, fs]);

  // look up where the vertex data needs to go.
  const positionAttributeLocation = gl.getAttribLocation(program, "a_position");

  // look up uniform locations
  const resolutionLocation = gl.getUniformLocation(program, "iResolution");
  const mouseLocation = gl.getUniformLocation(program, "iMouse");
  const timeLocation = gl.getUniformLocation(program, "iTime");

  // Create a vertex array object (attribute state)
  const vao = gl.createVertexArray();

  // and make it the one we're currently working with
  gl.bindVertexArray(vao);

  // Create a buffer to put three 2d clip space points in
  const positionBuffer = gl.createBuffer();

  // Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
  gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);

  // fill it with a 2 triangles that cover clip space
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
    -1, -1,  // first triangle
    1, -1,
    -1, 1,
    -1, 1,  // second triangle
    1, -1,
    1, 1,
  ]), gl.STATIC_DRAW);

  // Turn on the attribute
  gl.enableVertexAttribArray(positionAttributeLocation);

  // Tell the attribute how to get data out of positionBuffer (ARRAY_BUFFER)
  gl.vertexAttribPointer(
    positionAttributeLocation,
    2,          // 2 components per iteration
    gl.FLOAT,   // the data is 32bit floats
    false,      // don't normalize the data
    0,          // 0 = move forward size * sizeof(type) each iteration to get the next position
    0,          // start at the beginning of the buffer
  );

  function render(time) {
    time *= 0.001;  // convert to seconds

    webglUtils.resizeCanvasToDisplaySize(gl.canvas);

    // Tell WebGL how to convert from clip space to pixels
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

    // Tell it to use our program (pair of shaders)
    gl.useProgram(program);

    // Bind the attribute/buffer set we want.
    gl.bindVertexArray(vao);

    gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);

    gl.drawArrays(
      gl.TRIANGLES,
      0,     // offset
      6,     // num vertices to process
    );

    requestAnimationFrame(render);
  }
  requestAnimationFrame(render);
}

main();