1 | #include "common.h"
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2 | #include "SampleGenerator.h"
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3 |
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4 |
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5 | using namespace std;
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6 |
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7 | HaltonSequence SphericalSampleGenerator::sHalton;
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8 | HaltonSequence PoissonDiscSampleGenerator::sHalton;
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9 | HaltonSequence GaussianSampleGenerator::sHalton;
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10 | HaltonSequence PseudoRandomGenerator::sHalton;
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11 |
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12 |
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13 | SampleGenerator::SampleGenerator(int numSamples, float radius):
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14 | mNumSamples(numSamples), mRadius(radius)
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15 | {}
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16 |
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17 |
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18 | PoissonDiscSampleGenerator::PoissonDiscSampleGenerator(int numSamples, float radius):
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19 | SampleGenerator(numSamples, radius)
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20 | {}
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21 |
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22 |
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23 | void PoissonDiscSampleGenerator::Generate(float *samples) const
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24 | {
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25 | // this is a hacky poisson sampling generator which does random dart-throwing
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26 | // until it is not able to place any dart for a number of tries
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27 | // in this case, the required min distance is reduced
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28 | // the solution is a possion sampling with respect to the adjusted min distance
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29 | // better solutions have been proposed, i.e., using hierarchical sampling
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30 |
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31 | const float maxTries = 1000;
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32 | const float f_reduction = 0.9f;
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33 |
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34 | static HaltonSequence halton;
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35 | float r[2];
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36 |
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37 | // generates poisson distribution on disc
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38 | float minDist = 2.0f / sqrt((float)mNumSamples);
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39 |
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40 | //cout << "minDist before= " << minDist << endl;
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41 | Sample2 *s = (Sample2 *)samples;
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42 |
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43 | for (int i = 0; i < mNumSamples; ++ i)
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44 | {
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45 | int tries = 0, totalTries = 0;
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46 |
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47 | // repeat until valid sample was found
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48 | while (1)
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49 | {
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50 | ++ tries;
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51 | ++ totalTries;
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52 |
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53 | halton.GetNext(2, r);
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54 |
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55 | const float rx = r[0] * 2.0f - 1.0f;
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56 | const float ry = r[1] * 2.0f - 1.0f;
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57 |
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58 | // check if in disk, else exit early
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59 | if (rx * rx + ry * ry > 1)
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60 | continue;
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61 |
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62 | bool sampleValid = true;
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63 |
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64 | // check poisson property
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65 | for (int j = 0; ((j < i) && sampleValid); ++ j)
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66 | {
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67 | const float dist =
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68 | sqrt((s[j].x - rx) * (s[j].x - rx) +
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69 | (s[j].y - ry) * (s[j].y - ry));
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70 |
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71 | if (dist < minDist)
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72 | sampleValid = false;
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73 | }
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74 |
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75 | if (sampleValid)
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76 | {
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77 | s[i].x = rx;
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78 | s[i].y = ry;
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79 | break;
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80 | }
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81 |
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82 | if (tries > maxTries)
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83 | {
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84 | minDist *= f_reduction;
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85 | tries = 0;
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86 | }
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87 | }
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88 |
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89 | //cout << "sample: " << samples[i].x << " " << i << " " << samples[i].y << " r: " << sqrt(samples[i].x * samples[i].x + samples[i].y * samples[i].y) << " tries: " << totalTries << endl;
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90 | }
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91 |
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92 | //cout << "minDist after= " << minDist << endl;
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93 | }
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94 |
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95 |
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96 |
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97 | GaussianSampleGenerator::GaussianSampleGenerator(int numSamples, float radius):
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98 | SampleGenerator(numSamples, radius)
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99 | {}
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100 |
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101 |
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102 | void GaussianSampleGenerator::Generate(float *samples) const
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103 | {
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104 | float r[2];
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105 |
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106 | const float sigma = mRadius;
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107 |
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108 | Sample2 *s = (Sample2 *)samples;
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109 |
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110 | const float p0 = 1.0f / (sigma * sqrt(2.0f * M_PI));
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111 | const float p1 = 1.0f / (sigma * sqrt(2.0f * M_PI));
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112 |
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113 | for (int i = 0; i < mNumSamples; ++ i)
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114 | {
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115 | sHalton.GetNext(2, r);
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116 |
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117 | float exp_x = -(r[0] * r[0]) / (2.0f * sigma * sigma);
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118 | float exp_y = -(r[1] * r[1]) / (2.0f * sigma * sigma);
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119 |
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120 | s[i].x = p0 * pow(M_E, exp_x);
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121 | s[i].y = p1 * pow(M_E, exp_y);
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122 | }
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123 |
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124 | //cout << "minDist after= " << minDist << endl;
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125 | }
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126 |
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127 |
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128 | PseudoRandomGenerator::PseudoRandomGenerator(int numSamples, float radius):
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129 | SampleGenerator(numSamples, radius)
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130 | {}
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131 |
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132 |
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133 | void PseudoRandomGenerator::Generate(float *samples) const
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134 | {
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135 | sHalton.GetNext(2 * mNumSamples, samples);
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136 | }
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137 |
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138 |
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139 | SphericalSampleGenerator::SphericalSampleGenerator(int numSamples, float radius):
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140 | SampleGenerator(numSamples, radius)
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141 | {}
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142 |
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143 |
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144 | void SphericalSampleGenerator::Generate(float *samples) const
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145 | {
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146 | float r[2];
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147 | Sample3 *s = (Sample3 *)samples;
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148 | /*
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149 | // idea: use poisson distribution to generate samples
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150 |
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151 | PoissonDiscSampleGenerator poisson(mNumSamples, 1.0f);
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152 | Sample2 *pSamples = new Sample2[mNumSamples];
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153 | poisson.Generate((float *)pSamples);
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154 | */
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155 | for (int i = 0; i < mNumSamples; ++ i)
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156 | {
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157 | sHalton.GetNext(2, r);
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158 | //r[0] = pSamples[i].x; r[1] = pSamples[i].y;
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159 |
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160 | // create stratified samples over sphere
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161 | const float theta = 2.0f * acos(sqrt(1.0f - r[0]));
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162 | const float phi = 2.0f * M_PI * r[1];
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163 |
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164 | s[i].x = mRadius * sin(theta) * cos(phi);
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165 | s[i].y = mRadius * sin(theta) * sin(phi);
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166 | s[i].z = mRadius * cos(theta);
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167 | }
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168 |
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169 | //delete [] pSamples;
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170 | } |
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