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sampler.cpp
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sampler.cpp
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#include "sampler.hpp"
#include "spectrum.hpp"
#include "util.hpp"
using pupumath::vec3;
using pupumath::vec2;
struct LibCRandomSampler : public Sampler {
LibCRandomSampler(int n) : Sampler(n) {}
void generate() {}
float get_wavelen(int sample_id) override
{
return Spectrum::wavelen(frand());
}
vec2 get_lens(int sample_id) override { return vec2{frand(), frand()}; }
vec2 get_shading(int sample_id, int counter) override
{
return vec2{frand(), frand()};
}
};
struct LhsSampler : public Sampler {
std::unique_ptr<float[]> wavelen;
std::unique_ptr<pupumath::vec2[]> lens;
std::unique_ptr<pupumath::vec2[]> shading;
LhsSampler(int n)
: Sampler(n), wavelen(new float[n]), lens(new vec2[n]),
shading(new vec2[n * 4])
{
}
void generate() override
{
for (int i = 0; i < n; i++) {
wavelen[i] = Spectrum::wavelen((i + frand()) / n);
}
for (int i = 0; i < n; i++) {
lens[i] = vec2{frand(), frand()};
}
const float step = 1.f / n;
for (int k = 0; k < 4; k++) {
for (int i = 0; i < n; i++) {
shading[k * n + i] = vec2{(i + frand()) * step, (i + frand()) * step};
}
}
// Shuffle u1 values -> latin hypercube.
for (int k = 0; k < 4; k++) {
for (int i = 0; i < n - 1; i++) {
int j = i + rand() % (n - i);
std::swap(shading[k * n + i].x, shading[k * n + j].x);
}
}
// Shuffle samples so the different dimensions are not dependent.
for (int i = 0; i < n - 1; i++) {
int j = i + rand() % (n - i);
std::swap(wavelen[i], wavelen[j]);
}
for (int i = 0; i < n - 1; i++) {
int j = i + rand() % (n - i);
std::swap(lens[i], lens[j]);
}
for (int k = 0; k < 4; k++) {
for (int i = 0; i < n - 1; i++) {
int j = i + rand() % (n - i);
std::swap(shading[k * n + i], shading[k * n + j]);
}
}
}
float get_wavelen(int sample_id) override { return wavelen[sample_id]; }
vec2 get_lens(int sample_id) override { return lens[sample_id]; }
vec2 get_shading(int sample_id, int counter) override
{
if (counter < 4) {
return shading[counter * n + sample_id];
}
return vec2{frand(), frand()};
}
};
std::shared_ptr<Sampler> create_sampler(int n, const std::string& name)
{
if (name == "libcrandom")
return std::make_shared<LibCRandomSampler>(n);
else if (name == "lhs")
return std::make_shared<LhsSampler>(n);
else
throw std::runtime_error("unknown sampler '" + name + "'");
}