src/math/math-utils.js

/**
 * @file Math Utils
 * @author Alexander Rose <alexander.rose@weirdbyte.de>
 * @private
 */

function degToRad (deg) {
  return deg * 0.01745  // deg * Math.PI / 180
}

function radToDeg (rad) {
  return rad * 57.29578  // rad * 180 / Math.PI
}

// http://www.broofa.com/Tools/Math.uuid.htm
const chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.split('')
const uuid = new Array(36)

function generateUUID () {
  let rnd = 0
  var r

  for (let i = 0; i < 36; i++) {
    if (i === 8 || i === 13 || i === 18 || i === 23) {
      uuid[ i ] = '-'
    } else if (i === 14) {
      uuid[ i ] = '4'
    } else {
      if (rnd <= 0x02) rnd = 0x2000000 + (Math.random() * 0x1000000) | 0
      r = rnd & 0xf
      rnd = rnd >> 4
      uuid[ i ] = chars[ (i === 19) ? (r & 0x3) | 0x8 : r ]
    }
  }

  return uuid.join('')
}

function countSetBits (i) {
  i = i - ((i >> 1) & 0x55555555)
  i = (i & 0x33333333) + ((i >> 2) & 0x33333333)
  return (((i + (i >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24
}

function normalize (value, min, max) {
  return (value - min) / (max - min)
}

function clamp (value, min, max) {
  return Math.max(min, Math.min(max, value))
}

function pclamp (value) {
  return clamp(value, 0, 100)
}

function saturate (value) {
  return clamp(value, 0, 1)
}

function lerp (start, stop, alpha) {
  return start + (stop - start) * alpha
}

function spline (p0, p1, p2, p3, t, tension) {
  var v0 = (p2 - p0) * tension
  var v1 = (p3 - p1) * tension
  var t2 = t * t
  var t3 = t * t2
  return (2 * p1 - 2 * p2 + v0 + v1) * t3 +
         (-3 * p1 + 3 * p2 - 2 * v0 - v1) * t2 +
         v0 * t + p1
}

function smoothstep (min, max, x) {
  x = saturate(normalize(x, min, max))
  return x * x * (3 - 2 * x)
}

function smootherstep (min, max, x) {
  x = saturate(normalize(x, min, max))
  return x * x * x * (x * (x * 6 - 15) + 10)
}

function smootheststep (min, max, x) {
  x = saturate(normalize(x, min, max))
  return (
    -20 * Math.pow(x, 7) +
     70 * Math.pow(x, 6) -
     84 * Math.pow(x, 5) +
     35 * Math.pow(x, 4)
  )
}

function almostIdentity (value, start, stop) {
  if (value > start) return value
  const a = 2 * stop - start
  const b = 2 * start - 3 * stop
  const t = value / start
  return (a * t + b) * t * t + stop
}

export {
  degToRad,
  radToDeg,
  generateUUID,
  countSetBits,
  normalize,
  clamp,
  pclamp,
  saturate,
  lerp,
  spline,
  smoothstep,
  smootherstep,
  smootheststep,
  almostIdentity
}