71 lines
1.8 KiB
C++
71 lines
1.8 KiB
C++
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// This file is part of meshoptimizer library; see meshoptimizer.h for version/license details
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#include "meshoptimizer.h"
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#include <assert.h>
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unsigned short meshopt_quantizeHalf(float v)
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{
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union { float f; unsigned int ui; } u = {v};
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unsigned int ui = u.ui;
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int s = (ui >> 16) & 0x8000;
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int em = ui & 0x7fffffff;
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// bias exponent and round to nearest; 112 is relative exponent bias (127-15)
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int h = (em - (112 << 23) + (1 << 12)) >> 13;
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// underflow: flush to zero; 113 encodes exponent -14
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h = (em < (113 << 23)) ? 0 : h;
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// overflow: infinity; 143 encodes exponent 16
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h = (em >= (143 << 23)) ? 0x7c00 : h;
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// NaN; note that we convert all types of NaN to qNaN
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h = (em > (255 << 23)) ? 0x7e00 : h;
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return (unsigned short)(s | h);
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}
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float meshopt_quantizeFloat(float v, int N)
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{
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assert(N >= 0 && N <= 23);
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union { float f; unsigned int ui; } u = {v};
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unsigned int ui = u.ui;
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const int mask = (1 << (23 - N)) - 1;
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const int round = (1 << (23 - N)) >> 1;
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int e = ui & 0x7f800000;
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unsigned int rui = (ui + round) & ~mask;
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// round all numbers except inf/nan; this is important to make sure nan doesn't overflow into -0
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ui = e == 0x7f800000 ? ui : rui;
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// flush denormals to zero
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ui = e == 0 ? 0 : ui;
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u.ui = ui;
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return u.f;
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}
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float meshopt_dequantizeHalf(unsigned short h)
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{
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unsigned int s = unsigned(h & 0x8000) << 16;
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int em = h & 0x7fff;
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// bias exponent and pad mantissa with 0; 112 is relative exponent bias (127-15)
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int r = (em + (112 << 10)) << 13;
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// denormal: flush to zero
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r = (em < (1 << 10)) ? 0 : r;
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// infinity/NaN; note that we preserve NaN payload as a byproduct of unifying inf/nan cases
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// 112 is an exponent bias fixup; since we already applied it once, applying it twice converts 31 to 255
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r += (em >= (31 << 10)) ? (112 << 23) : 0;
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union { float f; unsigned int ui; } u;
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u.ui = s | r;
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return u.f;
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}
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