File size: 3,482 Bytes
b797337 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 | import { clamp } from '../math/MathUtils.js';
// Fast Half Float Conversions, http://www.fox-toolkit.org/ftp/fasthalffloatconversion.pdf
const _tables = /*@__PURE__*/ _generateTables();
function _generateTables() {
// float32 to float16 helpers
const buffer = new ArrayBuffer( 4 );
const floatView = new Float32Array( buffer );
const uint32View = new Uint32Array( buffer );
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 {
floatView: floatView,
uint32View: uint32View,
baseTable: baseTable,
shiftTable: shiftTable,
mantissaTable: mantissaTable,
exponentTable: exponentTable,
offsetTable: offsetTable
};
}
// float32 to float16
function toHalfFloat( val ) {
if ( Math.abs( val ) > 65504 ) console.warn( 'THREE.DataUtils.toHalfFloat(): Value out of range.' );
val = clamp( val, - 65504, 65504 );
_tables.floatView[ 0 ] = val;
const f = _tables.uint32View[ 0 ];
const e = ( f >> 23 ) & 0x1ff;
return _tables.baseTable[ e ] + ( ( f & 0x007fffff ) >> _tables.shiftTable[ e ] );
}
// float16 to float32
function fromHalfFloat( val ) {
const m = val >> 10;
_tables.uint32View[ 0 ] = _tables.mantissaTable[ _tables.offsetTable[ m ] + ( val & 0x3ff ) ] + _tables.exponentTable[ m ];
return _tables.floatView[ 0 ];
}
const DataUtils = {
toHalfFloat: toHalfFloat,
fromHalfFloat: fromHalfFloat,
};
export {
toHalfFloat,
fromHalfFloat,
DataUtils
};
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