1 | #include "SampleGenerator.h"
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2 | #include "common.h"
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3 |
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4 |
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5 | using namespace std;
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6 | using namespace CHCDemoEngine;
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7 |
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8 |
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9 | SampleGenerator::SampleGenerator(int numSamples, float radius):
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10 | mNumSamples(numSamples), mRadius(radius)
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11 | {
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12 | mHalton = new HaltonSequence(2);
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13 | }
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14 |
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15 |
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16 | SampleGenerator::~SampleGenerator()
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17 | {
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18 | DEL_PTR(mHalton);
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19 | }
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20 |
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21 |
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22 | PoissonDiscSampleGenerator2D::PoissonDiscSampleGenerator2D(int numSamples, float radius):
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23 | SampleGenerator(numSamples, radius)
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24 | {}
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25 |
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26 |
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27 | void PoissonDiscSampleGenerator2D::Generate(float *samples) const
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28 | {
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29 | // Poisson disc sampling generator using relaxation
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30 | // dart-throwing as proposed by McCool et al.
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31 | // the min distance requirement is relaxed if we are not
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32 | // able to place any dart for a number of tries
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33 | // the solution is a possion sampling with respect
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34 | // to the adjusted min distance
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35 | // this sampling scheme has the benefit that it is hierarchical
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36 | int maxTries = 1000;
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37 | const float f_reduction = 0.9f;
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38 |
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39 | float r[2];
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40 |
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41 | // generates poisson distribution on disc
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42 | // start with some threshold
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43 | // best case: all samples lie on the circumference of circle
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44 |
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45 | const float eps = 0.2f;
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46 | const float minDist = 2.0f * mRadius * M_PI * (1.0f - eps) / (float)mNumSamples;
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47 | float sqrMinDist = minDist * minDist;
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48 |
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49 | //cout << "minDist before= " << minDist << endl;
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50 | Sample2 *s = (Sample2 *)samples;
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51 |
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52 | int totalTries = 0;
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53 |
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54 | // check if on disc
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55 | for (int i = 0; i < mNumSamples; ++ i)
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56 | {
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57 | int tries = 0;
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58 |
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59 | // repeat until valid sample was found
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60 | while (1)
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61 | {
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62 | ++ tries;
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63 | ++ totalTries;
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64 |
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65 | // note: should use halton, but seems somewhat broken
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66 | mHalton->GetNext(r);
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67 |
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68 | // scale to -1 .. 1
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69 | const float rx = r[0] * 2.0f - 1.0f;
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70 | const float ry = r[1] * 2.0f - 1.0f;
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71 |
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72 | // check if in disk, else exit early
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73 | const float distanceSquared = rx * rx + ry * ry;
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74 |
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75 | if ((rx * rx + ry * ry > mRadius * mRadius)
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76 | // also avoid case that sample exactly in center
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77 | //|| (distanceSquared <= 1e-3f)
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78 | )
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79 | continue;
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80 |
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81 | bool sampleValid = true;
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82 |
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83 | // check poisson property
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84 | for (int j = 0; ((j < i) && sampleValid); ++ j)
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85 | {
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86 | const float dist =
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87 | (s[j].x - rx) * (s[j].x - rx) +
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88 | (s[j].y - ry) * (s[j].y - ry);
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89 |
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90 | if (dist < sqrMinDist)
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91 | sampleValid = false;
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92 | }
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93 |
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94 | if (sampleValid)
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95 | {
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96 | s[i].x = rx;
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97 | s[i].y = ry;
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98 | break;
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99 | }
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100 |
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101 | if (tries > maxTries)
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102 | {
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103 | sqrMinDist *= f_reduction;
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104 | tries = 0;
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105 | }
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106 | }
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107 | }
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108 |
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109 | cout << "minDist after= " << sqrt(sqrMinDist) << " #tries: " << totalTries << endl;
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110 | }
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111 |
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112 |
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113 | RandomSampleGenerator2D::RandomSampleGenerator2D(int numSamples, float radius):
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114 | SampleGenerator(numSamples, radius)
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115 | {}
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116 |
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117 |
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118 | void RandomSampleGenerator2D::Generate(float *samples) const
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119 | {
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120 | Sample2 *s = (Sample2 *)samples;
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121 |
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122 | int numSamples = 0;
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123 |
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124 | float r[2];
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125 |
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126 | while (numSamples < mNumSamples)
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127 | {
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128 | mHalton->GetNext(r);
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129 |
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130 | const float rx = r[0] * 2.0f - 1.0f;
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131 | const float ry = r[1] * 2.0f - 1.0f;
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132 |
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133 | // check if in disk, else exit early
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134 | if (rx * rx + ry * ry > mRadius * mRadius)
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135 | continue;
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136 |
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137 | s[numSamples].x = rx;
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138 | s[numSamples].y = ry;
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139 |
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140 | ++ numSamples;
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141 | }
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142 | }
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143 |
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144 |
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145 | SphericalSampleGenerator3D::SphericalSampleGenerator3D(int numSamples, float radius):
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146 | SampleGenerator(numSamples, radius)
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147 | {}
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148 |
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149 |
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150 | void SphericalSampleGenerator3D::Generate(float *samples) const
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151 | {
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152 | float r[2];
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153 | Sample3 *s = (Sample3 *)samples;
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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 | r[0] = RandomValue(0, 1);
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158 | r[1] = RandomValue(0, 1);
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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 |
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170 |
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171 | QuadraticDiscSampleGenerator2D::QuadraticDiscSampleGenerator2D(int numSamples, float radius):
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172 | PoissonDiscSampleGenerator2D(numSamples, radius)
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173 | {}
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174 |
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175 |
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176 | void QuadraticDiscSampleGenerator2D::Generate(float *samples) const
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177 | {
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178 | #if 0
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179 | float r[2];
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180 | Sample2 *s = (Sample2 *)samples;
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181 |
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182 | for (int i = 0; i < mNumSamples; ++ i)
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183 | {
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184 | mHalton->GetNext(r);
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185 |
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186 | // create samples over disc: the sample density
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187 | // decreases quadratically with the distance to the origin
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188 | s[i].x = mRadius * r[1] * sin(2.0f * M_PI * r[0]);
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189 | s[i].y = mRadius * r[1] * cos(2.0f * M_PI * r[0]);
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190 | }
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191 | #else
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192 |
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193 | PoissonDiscSampleGenerator2D::Generate(samples);
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194 |
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195 | Sample2 *s = (Sample2 *)samples;
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196 |
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197 | // multiply with lenght to get quadratic dependence on the distance
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198 | for (int i = 0; i < mNumSamples; ++ i)
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199 | {
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200 | Sample2 &spl = s[i];
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201 |
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202 | float len = sqrt(spl.x * spl.x + spl.y * spl.y);
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203 | spl.x *= len * mRadius;
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204 | spl.y *= len * mRadius;
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205 | }
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206 | #endif
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207 | } |
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