1 #ifndef PtexHalf_h 2 #define PtexHalf_h 3 4 /* 5 PTEX SOFTWARE 6 Copyright 2014 Disney Enterprises, Inc. All rights reserved 7 8 Redistribution and use in source and binary forms, with or without 9 modification, are permitted provided that the following conditions are 10 met: 11 12 * Redistributions of source code must retain the above copyright 13 notice, this list of conditions and the following disclaimer. 14 15 * Redistributions in binary form must reproduce the above copyright 16 notice, this list of conditions and the following disclaimer in 17 the documentation and/or other materials provided with the 18 distribution. 19 20 * The names "Disney", "Walt Disney Pictures", "Walt Disney Animation 21 Studios" or the names of its contributors may NOT be used to 22 endorse or promote products derived from this software without 23 specific prior written permission from Walt Disney Pictures. 24 25 Disclaimer: THIS SOFTWARE IS PROVIDED BY WALT DISNEY PICTURES AND 26 CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, 27 BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS 28 FOR A PARTICULAR PURPOSE, NONINFRINGEMENT AND TITLE ARE DISCLAIMED. 29 IN NO EVENT SHALL WALT DISNEY PICTURES, THE COPYRIGHT HOLDER OR 30 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 31 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 32 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 33 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND BASED ON ANY 34 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 36 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 37 */ 38 39 /** 40 @file PtexHalf.h 41 @brief Half-precision floating-point type. 42 */ 43 44 #ifndef PTEXAPI 45 # if defined(_WIN32) || defined(_WINDOWS) || defined(_MSC_VER) 46 # ifndef PTEX_STATIC 47 # ifdef PTEX_EXPORTS 48 # define PTEXAPI __declspec(dllexport) 49 # else 50 # define PTEXAPI __declspec(dllimport) 51 # endif 52 # else 53 # define PTEXAPI 54 # endif 55 # else 56 # define PTEXAPI 57 # endif 58 #endif 59 60 #include "PtexInt.h" 61 62 #include "PtexVersion.h" 63 64 PTEX_NAMESPACE_BEGIN 65 66 /** 67 @class PtexHalf 68 @brief Half-precision (16-bit) floating-point type. 69 70 This type should be compatible with opengl, openexr, and IEEE 754r. 71 The range is [-65504.0, 65504.0] and the precision is about 1 part 72 in 2000 (3.3 decimal places). 73 74 From OpenGL spec 2.1.2: 75 76 A 16-bit floating-point number has a 1-bit sign (S), a 5-bit 77 exponent (E), and a 10-bit mantissa (M). The value of a 16-bit 78 floating-point number is determined by the following: 79 80 \verbatim 81 (-1)^S * 0.0, if E == 0 and M == 0, 82 (-1)^S * 2^-14 * (M/2^10), if E == 0 and M != 0, 83 (-1)^S * 2^(E-15) * (1 + M/2^10), if 0 < E < 31, 84 (-1)^S * INF, if E == 31 and M == 0, or 85 NaN, if E == 31 and M != 0 \endverbatim 86 */ 87 88 struct PtexHalf { 89 uint16_t bits; 90 91 /// Default constructor, value is undefined PtexHalfPtexHalf92 PtexHalf() {} PtexHalfPtexHalf93 PtexHalf(float val) : bits(fromFloat(val)) {} PtexHalfPtexHalf94 PtexHalf(double val) : bits(fromFloat(float(val))) {} 95 operator float() const { return toFloat(bits); } 96 PtexHalf& operator=(float val) { bits = fromFloat(val); return *this; } 97 toFloatPtexHalf98 static float toFloat(uint16_t h) 99 { 100 union { uint32_t i; float f; } u; 101 u.i = h2fTable[h]; 102 return u.f; 103 } 104 fromFloatPtexHalf105 static uint16_t fromFloat(float val) 106 { 107 if (val==0) return 0; 108 union { uint32_t i; float f; } u; 109 u.f = val; 110 int e = f2hTable[(u.i>>23)&0x1ff]; 111 if (e) return (uint16_t)(e + (((u.i&0x7fffff) + 0x1000) >> 13)); 112 return fromFloat_except(u.i); 113 } 114 115 private: 116 PTEXAPI static uint16_t fromFloat_except(uint32_t val); 117 #ifndef DOXYGEN 118 /* internal */ public: 119 #endif 120 PTEXAPI static uint32_t h2fTable[65536]; 121 PTEXAPI static uint16_t f2hTable[512]; 122 }; 123 124 PTEX_NAMESPACE_END 125 126 using Ptex::PtexHalf; 127 128 #endif 129