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WebGL Particles in Sphere

  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.   const pointSize = Math.max(Math.min(30, ~~(innerWidth / 70)), 3)
  9.  
  10.   const vert = `
  11.     attribute vec3 vec;
  12.     uniform mat4 mat;
  13.     void main(void) {
  14.       gl_Position = mat * vec4(vec, 1.0);
  15.       gl_PointSize = ${pointSize}.0;
  16.     }
  17.   `
  18.  
  19.   const frag = `
  20.     void main(void) {
  21.       gl_FragColor = vec4(1., 1., 1., .25);
  22.     }
  23.   `
  24.  
  25.   document.body.style.background = '#232323'
  26.   const gl = document.body
  27.     .appendChild(document.createElement('canvas'))
  28.     .getContext('webgl', {
  29.       preserveDrawingBuffer: true,
  30.       powerPreference: 'high-performance'
  31.     })
  32.  
  33.   Object.assign(gl.canvas.style, {
  34.     position: 'absolute',
  35.     left: '50%',
  36.     top: '50%',
  37.     transform: 'translate(-50%, -50%)',
  38.     outline: '1px solid gray'
  39.   })
  40.  
  41.   with (gl) {
  42.     const NUM = 4000
  43.     const radius = 0.7
  44.     const verts = []
  45.  
  46.     for (let i = 0; i < NUM; i += 3) {
  47.       let xp = Math.random() * 2 - 1
  48.       let yp = Math.random() * 2 - 1
  49.       let zp = Math.random() * 2 - 1
  50.       let dist = Math.sqrt(xp * xp + yp * yp + zp * zp)
  51.       // normalize and scale x,y,z
  52.       verts[i] = (xp / dist) * radius
  53.       verts[i + 1] = (yp / dist) * radius
  54.       verts[i + 2] = (zp / dist) * radius
  55.  
  56.     }
  57.     const overts = verts.concat()
  58.     const leng = verts.length / 3
  59.  
  60.     bindBuffer(ARRAY_BUFFER, createBuffer())
  61.     bufferData(ARRAY_BUFFER, new Float32Array(verts), STATIC_DRAW)
  62.  
  63.     const vs = createShader(VERTEX_SHADER)
  64.     shaderSource(vs, vert)
  65.     compileShader(vs)
  66.  
  67.     const fs = createShader(FRAGMENT_SHADER)
  68.     const sp = createProgram()
  69.  
  70.     shaderSource(fs, frag)
  71.     compileShader(fs)
  72.     attachShader(sp, vs)
  73.     attachShader(sp, fs)
  74.     linkProgram(sp)
  75.     useProgram(sp)
  76.  
  77.     const vec = getAttribLocation(sp, 'vec')
  78.     vertexAttribPointer(vec, 3, FLOAT, false, 0, 0)
  79.     enableVertexAttribArray(vec)
  80.  
  81.     const matLoc = getUniformLocation(sp, 'mat')
  82.  
  83.     function rot(x, y, z) {
  84.       // https://wikimedia.org/api/rest_v1/media/math/render/svg/a8e16f4967571b7a572d1a19f3f6468512f9843e
  85.  
  86.       const sinA = Math.sin(x)
  87.       const cosA = Math.cos(x)
  88.       const sinB = Math.sin(y)
  89.       const cosB = Math.cos(y)
  90.       const sinY = Math.sin(z)
  91.       const cosY = Math.cos(z)
  92.  
  93.       m[0] = cosA * cosB
  94.       m[1] = cosA * sinB * sinY - sinA * cosY
  95.       m[2] = cosA * sinB * cosY + sinA * sinY
  96.       m[3] = 0
  97.  
  98.       m[4] = sinA * cosB
  99.       m[5] = sinA * sinB * sinY + cosA * cosY
  100.       m[6] = sinA * sinB * cosY - cosA * sinY
  101.       m[7] = 0
  102.  
  103.       m[8] = -sinB
  104.       m[9] = cosB * sinY
  105.       m[10] = cosB * cosY
  106.       m[11] = m[12] = m[13] = 0
  107.       m[15] = 1
  108.  
  109.       uniformMatrix4fv(matLoc, false, m)
  110.     }
  111.  
  112.     onresize = () => {
  113.       const { canvas } = gl
  114.       const size = Math.min(innerWidth, innerHeight) - 20
  115.       canvas.width = canvas.height = size
  116.       viewport(0, 0, size, size)
  117.     }
  118.  
  119.     onresize()
  120.  
  121.     let rx = 0,
  122.       ry = 0,
  123.       rz = 0
  124.     let t = 0
  125.  
  126.     function loop() {
  127.       rx += 0.01
  128.       ry += 0.01
  129.       rot(rx, ry, rz)
  130.  
  131.       disable(DEPTH_TEST)
  132.       enable(BLEND)
  133.       blendFunc(SRC_ALPHA, ONE_MINUS_SRC_ALPHA)
  134.  
  135.       clearColor(0, 0, 0, 1)
  136.  
  137.       clear(COLOR_BUFFER_BIT)
  138.  
  139.       for (let i = 0; i < verts.length; i += 3) {
  140.         let tof = i * 0.001 + t;
  141.         verts[i] = Math.sin(tof) * overts[i]
  142.         verts[i + 1] = Math.sin(tof) * overts[i + 1]
  143.         verts[i + 2] = Math.sin(tof) * overts[i + 2]
  144.       }
  145.  
  146.       t += 0.01
  147.  
  148.       bufferSubData(ARRAY_BUFFER, 0, new Float32Array(verts))
  149.  
  150.       drawArrays(POINTS, 0, leng)
  151.       window.requestAnimationFrame(loop)
  152.     }
  153.     loop()
  154.   }
  155. })()

Playing around with animating points…

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