@luma.gl/shadertools
Version:
Shader module system for luma.gl
117 lines • 3.87 kB
JavaScript
// luma.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
// Forked from THREE.js under MIT license
// Fast Half Float Conversions, http://www.fox-toolkit.org/ftp/fasthalffloatconversion.pdf
import { clamp } from '@math.gl/core';
/** */
let float16Tables = null;
/** Storage that can be viewed both as float and integer */
const buffer = new ArrayBuffer(4);
const floatView = new Float32Array(buffer);
const uint32View = new Uint32Array(buffer);
/**
* float32 to float16
* @param val
* @returns
*/
export function toHalfFloat(val) {
float16Tables ||= generateFloat16Tables();
// if ( Math.abs( val ) > 65504 ) console.warn( 'toHalfFloat(): Value out of range.' );
val = clamp(val, -65504, 65504);
floatView[0] = val;
const f = uint32View[0];
const e = (f >> 23) & 0x1ff;
return float16Tables.baseTable[e] + ((f & 0x007fffff) >> float16Tables.shiftTable[e]);
}
/**
* float16 to float32
* @param val
* @returns
*/
export function fromHalfFloat(val) {
float16Tables ||= generateFloat16Tables();
const m = val >> 10;
uint32View[0] =
float16Tables.mantissaTable[float16Tables.offsetTable[m] + (val & 0x3ff)] +
float16Tables.exponentTable[m];
return floatView[0];
}
function generateFloat16Tables() {
// float32 to float16 helpers
const baseTable = new Uint32Array(512);
const shiftTable = new Uint32Array(512);
for (let i = 0; i < 256; ++i) {
const e = i - 127;
// very small number (0, -0)
if (e < -27) {
baseTable[i] = 0x0000;
baseTable[i | 0x100] = 0x8000;
shiftTable[i] = 24;
shiftTable[i | 0x100] = 24;
// small number (denorm)
}
else if (e < -14) {
baseTable[i] = 0x0400 >> (-e - 14);
baseTable[i | 0x100] = (0x0400 >> (-e - 14)) | 0x8000;
shiftTable[i] = -e - 1;
shiftTable[i | 0x100] = -e - 1;
// normal number
}
else if (e <= 15) {
baseTable[i] = (e + 15) << 10;
baseTable[i | 0x100] = ((e + 15) << 10) | 0x8000;
shiftTable[i] = 13;
shiftTable[i | 0x100] = 13;
// large number (Infinity, -Infinity)
}
else if (e < 128) {
baseTable[i] = 0x7c00;
baseTable[i | 0x100] = 0xfc00;
shiftTable[i] = 24;
shiftTable[i | 0x100] = 24;
// stay (NaN, Infinity, -Infinity)
}
else {
baseTable[i] = 0x7c00;
baseTable[i | 0x100] = 0xfc00;
shiftTable[i] = 13;
shiftTable[i | 0x100] = 13;
}
}
// float16 to float32 helpers
const mantissaTable = new Uint32Array(2048);
const exponentTable = new Uint32Array(64);
const offsetTable = new Uint32Array(64);
for (let i = 1; i < 1024; ++i) {
let m = i << 13; // zero pad mantissa bits
let e = 0; // zero exponent
// normalized
while ((m & 0x00800000) === 0) {
m <<= 1;
e -= 0x00800000; // decrement exponent
}
m &= ~0x00800000; // clear leading 1 bit
e += 0x38800000; // adjust bias
mantissaTable[i] = m | e;
}
for (let i = 1024; i < 2048; ++i) {
mantissaTable[i] = 0x38000000 + ((i - 1024) << 13);
}
for (let i = 1; i < 31; ++i) {
exponentTable[i] = i << 23;
}
exponentTable[31] = 0x47800000;
exponentTable[32] = 0x80000000;
for (let i = 33; i < 63; ++i) {
exponentTable[i] = 0x80000000 + ((i - 32) << 23);
}
exponentTable[63] = 0xc7800000;
for (let i = 1; i < 64; ++i) {
if (i !== 32) {
offsetTable[i] = 1024;
}
}
return { baseTable, shiftTable, mantissaTable, exponentTable, offsetTable };
}
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