backend/libs/three/extras/DataUtils.js

const _floatView = new Float32Array(1);
const _int32View = new Int32Array(_floatView.buffer);

class DataUtils {
	// Converts float32 to float16 (stored as uint16 value).

	static toHalfFloat(val) {
		if (val > 65504) {
			console.warn('THREE.DataUtils.toHalfFloat(): value exceeds 65504.');

			val = 65504; // maximum representable value in float16
		}

		// 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;
		const x = _int32View[0];

		let bits = (x >> 16) & 0x8000; /* Get the sign */
		let m = (x >> 12) & 0x07ff; /* Keep one extra bit for rounding */
		const 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;
			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;
	}
}

export { DataUtils };