toHalfFloat static method

int toHalfFloat(num val)

Implementation

static int toHalfFloat(num val) {
  // Source: http://gamedev.stackexchange.com/questions/17326/conversion-of-a-number-from-single-precision-floating-point-representation-to-a/17410#17410

  /* This method is faster than the OpenEXR implementation (very often
		* used, eg. in Ogre), with the additional benefit of rounding, inspired
		* by James Tursa?s half-precision code. */

  _floatView[0] = val.toDouble();
  var x = _int32View[0];

  var bits = (x >> 16) & 0x8000; /* Get the sign */
  var m = (x >> 12) & 0x07ff; /* Keep one extra bit for rounding */
  var e = (x >> 23) & 0xff; /* Using int is faster here */

  /* If zero, or denormal, or exponent underflows too much for a denormal
			* half, return signed zero. */
  if (e < 103) return bits;

  /* If NaN, return NaN. If Inf or exponent overflow, return Inf. */
  if (e > 142) {
    bits |= 0x7c00;
    /* If exponent was 0xff and one mantissa bit was set, it means NaN,
						* not Inf, so make sure we set one mantissa bit too. */
    // bits |= ( ( e == 255 ) ? 0 : 1 ) && ( x & 0x007fffff );
    bits |= (e == 255 ? (x & 0x007fffff) : 1);

    return bits;
  }

  /* If exponent underflows but not too much, return a denormal */
  if (e < 113) {
    m |= 0x0800;
    /* Extra rounding may overflow and set mantissa to 0 and exponent
				* to 1, which is OK. */
    bits |= (m >> (114 - e)) + ((m >> (113 - e)) & 1);
    return bits;
  }

  bits |= ((e - 112) << 10) | (m >> 1);
  /* Extra rounding. An overflow will set mantissa to 0 and increment
			* the exponent, which is OK. */
  bits += m & 1;
  return bits;
}