OpenVDB: openvdb/math/QuantizedUnitVec.h Source File

OpenVDB 9.0.0

QuantizedUnitVec.h
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1// Copyright Contributors to the OpenVDB Project
2// SPDX-License-Identifier: MPL-2.0
3
4#ifndef OPENVDB_MATH_QUANTIZED_UNIT_VEC_HAS_BEEN_INCLUDED
5#define OPENVDB_MATH_QUANTIZED_UNIT_VEC_HAS_BEEN_INCLUDED
6
7#include <openvdb/Platform.h>
8#include <openvdb/version.h>
9#include "Vec3.h"
10
11namespace openvdb {
12 OPENVDB_USE_VERSION_NAMESPACE
13namespace OPENVDB_VERSION_NAME {
14namespace math {
15
16/// @brief Unit vector occupying only 16 bits
17/// @details Stores two quantized components. Based on the
18/// "Higher Accuracy Quantized Normals" article from GameDev.Net LLC, 2000
19 class OPENVDB_API QuantizedUnitVec
20{
21public:
22 template<typename T> static uint16_t pack(const Vec3<T>& vec);
23 static Vec3s unpack(const uint16_t data);
24
25 static void flipSignBits(uint16_t&);
26
27private:
28 QuantizedUnitVec() {}
29
30 // bit masks
31 static const uint16_t MASK_SLOTS = 0x1FFF; // 0001111111111111
32 static const uint16_t MASK_XSLOT = 0x1F80; // 0001111110000000
33 static const uint16_t MASK_YSLOT = 0x007F; // 0000000001111111
34 static const uint16_t MASK_XSIGN = 0x8000; // 1000000000000000
35 static const uint16_t MASK_YSIGN = 0x4000; // 0100000000000000
36 static const uint16_t MASK_ZSIGN = 0x2000; // 0010000000000000
37
38 // normalization weights, 32 kilobytes.
39 static float sNormalizationWeights[MASK_SLOTS + 1];
40}; // class QuantizedUnitVec
41
42
43////////////////////////////////////////
44
45
46template<typename T>
47inline uint16_t
48QuantizedUnitVec::pack(const Vec3<T>& vec)
49{
50 if (math::isZero(vec)) return 0;
51
52 uint16_t data = 0;
53 T x(vec[0]), y(vec[1]), z(vec[2]);
54
55 // The sign of the three components are first stored using
56 // 3-bits and can then safely be discarded.
57 if (x < T(0.0)) { data |= MASK_XSIGN; x = -x; }
58 if (y < T(0.0)) { data |= MASK_YSIGN; y = -y; }
59 if (z < T(0.0)) { data |= MASK_ZSIGN; z = -z; }
60
61 // The z component is discarded and x & y are quantized in
62 // the 0 to 126 range.
63 T w = T(126.0) / (x + y + z);
64 uint16_t xbits = static_cast<uint16_t>((x * w));
65 uint16_t ybits = static_cast<uint16_t>((y * w));
66
67 // The remaining 13 bits in our 16 bit word are dividied into a
68 // 6-bit x-slot and a 7-bit y-slot. Both the xbits and the ybits
69 // can still be represented using (2^7 - 1) quantization levels.
70
71 // If the xbits requre more than 6-bits, store the complement.
72 // (xbits + ybits < 127, thus if xbits > 63 => ybits <= 63)
73 if (xbits > 63) {
74 xbits = static_cast<uint16_t>(127 - xbits);
75 ybits = static_cast<uint16_t>(127 - ybits);
76 }
77
78 // Pack components into their respective slots.
79 data = static_cast<uint16_t>(data | (xbits << 7));
80 data = static_cast<uint16_t>(data | ybits);
81 return data;
82}
83
84
85inline Vec3s
86QuantizedUnitVec::unpack(const uint16_t data)
87{
88 const float w = sNormalizationWeights[data & MASK_SLOTS];
89
90 uint16_t xbits = static_cast<uint16_t>((data & MASK_XSLOT) >> 7);
91 uint16_t ybits = static_cast<uint16_t>(data & MASK_YSLOT);
92
93 // Check if the complement components where stored and revert.
94 if ((xbits + ybits) > 126) {
95 xbits = static_cast<uint16_t>(127 - xbits);
96 ybits = static_cast<uint16_t>(127 - ybits);
97 }
98
99 Vec3s vec(float(xbits) * w, float(ybits) * w, float(126 - xbits - ybits) * w);
100
101 if (data & MASK_XSIGN) vec[0] = -vec[0];
102 if (data & MASK_YSIGN) vec[1] = -vec[1];
103 if (data & MASK_ZSIGN) vec[2] = -vec[2];
104 return vec;
105}
106
107
108////////////////////////////////////////
109
110
111inline void
112QuantizedUnitVec::flipSignBits(uint16_t& v)
113{
114 v = static_cast<uint16_t>((v & MASK_SLOTS) | (~v & ~MASK_SLOTS));
115}
116
117} // namespace math
118} // namespace OPENVDB_VERSION_NAME
119} // namespace openvdb
120
121#endif // OPENVDB_MATH_QUANTIZED_UNIT_VEC_HAS_BEEN_INCLUDED
Platform.h
OPENVDB_API
#define OPENVDB_API
Definition: Platform.h:254
Vec3.h
openvdb::v9_0::math::QuantizedUnitVec
Unit vector occupying only 16 bits.
Definition: QuantizedUnitVec.h:20
openvdb::v9_0::math::Vec3
Definition: Vec3.h:24
openvdb::v9_0::math::isZero
bool isZero(const Type &x)
Return true if x is exactly equal to zero.
Definition: Math.h:338
openvdb
Definition: Exceptions.h:13
OPENVDB_VERSION_NAME
#define OPENVDB_VERSION_NAME
The version namespace name for this library version.
Definition: version.h.in:116
OPENVDB_USE_VERSION_NAMESPACE
#define OPENVDB_USE_VERSION_NAMESPACE
Definition: version.h.in:202