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}

WebGL Points and Rotation

  1. (() => {
  2.   const m = new Float32Array([
  3.     0, 0, 0, 0, 
  4.     0, 0, 0, 0, 
  5.     0, 0, 0, 0, 
  6.     0, 0, 0, 0
  7.   ])
  8.  
  9.   const pointSize = Math.max(Math.min(10, ~~(innerWidth / 70)), 3);
  10.  
  11.   const vert = `
  12.     attribute vec3 vec;
  13.     uniform mat4 mat;
  14.     void main(void) {
  15.       gl_Position = mat * vec4(vec, 1.);
  16.       gl_PointSize = ${pointSize}.;
  17.     }
  18.   `
  19.  
  20.   const frag = `
  21.     void main(void) {
  22.       gl_FragColor = vec4(1., 1., 1., .4);
  23.     }
  24.   `
  25.  
  26.   document.body.style.background = '#333'
  27.   const gl = document.body
  28.     .appendChild(document.createElement('canvas'))
  29.     .getContext('webgl')
  30.  
  31.   Object.assign(gl.canvas.style, {
  32.     position: 'absolute',
  33.     left: '50%',
  34.     top: '50%',
  35.     transform: 'translate(-50%, -50%)',
  36.     outline: '1px solid gray'
  37.   })
  38.  
  39.   with (gl) {
  40.     const NUM = 600
  41.     const verts = []
  42.  
  43.     for (let i = 0; i < NUM; i++) {
  44.       verts.push(
  45.         Math.random() * 1 - 0.5,
  46.         Math.random() * 1 - 0.5,
  47.         Math.random() * 1 - 0.5
  48.       )
  49.     }
  50.  
  51.     const leng = verts.length / 3
  52.     bindBuffer(ARRAY_BUFFER, createBuffer())
  53.     bufferData(ARRAY_BUFFER, new Float32Array(verts), STATIC_DRAW)
  54.  
  55.     const vs = createShader(VERTEX_SHADER)
  56.     shaderSource(vs, vert)
  57.     compileShader(vs)
  58.  
  59.     const fs = createShader(FRAGMENT_SHADER)
  60.     const sp = createProgram()
  61.  
  62.     shaderSource(fs, frag)
  63.     compileShader(fs)
  64.     attachShader(sp, vs)
  65.     attachShader(sp, fs)
  66.     linkProgram(sp)
  67.     useProgram(sp)
  68.  
  69.     const vec = getAttribLocation(sp, 'vec')
  70.     vertexAttribPointer(vec, 3, FLOAT, false, 0, 0)
  71.     enableVertexAttribArray(vec)
  72.  
  73.     const matLoc = getUniformLocation(sp, 'mat')
  74.  
  75.     function rot(x, y, z) {
  76.       // https://wikimedia.org/api/rest_v1/media/math/render/svg/a8e16f4967571b7a572d1a19f3f6468512f9843e
  77.  
  78.       const sinA = Math.sin(x)
  79.       const cosA = Math.cos(x)
  80.       const sinB = Math.sin(y)
  81.       const cosB = Math.cos(y)
  82.       const sinY = Math.sin(z)
  83.       const cosY = Math.cos(z)
  84.  
  85.       m[0] = cosA * cosB
  86.       m[1] = cosA * sinB * sinY - sinA * cosY
  87.       m[2] = cosA * sinB * cosY + sinA * sinY
  88.       m[3] = 0
  89.  
  90.       m[4] = sinA * cosB
  91.       m[5] = sinA * sinB * sinY + cosA * cosY
  92.       m[6] = sinA * sinB * cosY - cosA * sinY
  93.       m[7] = 0
  94.  
  95.       m[8] = -sinB
  96.       m[9] = cosB * sinY
  97.       m[10] = cosB * cosY
  98.       m[11] = m[12] = m[13] = 0
  99.       m[15] = 1
  100.  
  101.       uniformMatrix4fv(matLoc, false, m)
  102.     }
  103.  
  104.     onresize = () => {
  105.       const { canvas } = gl
  106.       const size = Math.min(innerWidth, innerHeight) - 20
  107.       canvas.width = canvas.height = size
  108.       viewport(0, 0, size, size)
  109.     }
  110.  
  111.     onresize()
  112.  
  113.     let ry = 0, rz = 0
  114.  
  115.     disable(DEPTH_TEST)
  116.     enable(BLEND)
  117.     blendFunc(SRC_ALPHA, ONE_MINUS_SRC_ALPHA)
  118.  
  119.     function loop() {
  120.       rot(0, ry -= 0.03, rz += 0.001)
  121.  
  122.       clearColor(0, 0, 0, 1)
  123.       clear(COLOR_BUFFER_BIT)
  124.       drawArrays(POINTS, 0, leng)
  125.       window.requestAnimationFrame(loop)
  126.     }
  127.     loop()
  128.   }
  129. })()

Some WebGL points with rotation… I couldn’t resist using with here…

snippet.zone ~ 2021-22 /// {s/z}