From 15feef3a9784ab337eb8a6942160cefc0fa1f24b Mon Sep 17 00:00:00 2001
From: Yoel <s73017@beuth-hochschule.de>
Date: Mon, 29 Mar 2021 17:42:14 +0200
Subject: [PATCH] EmissionProfile implemented
---
RayTracer/tools/EmissionProfile.cpp | 101 ++++++++++++++++++++++++++++
RayTracer/tools/EmissionProfile.h | 36 ++++++++++
2 files changed, 137 insertions(+)
create mode 100644 RayTracer/tools/EmissionProfile.cpp
create mode 100644 RayTracer/tools/EmissionProfile.h
diff --git a/RayTracer/tools/EmissionProfile.cpp b/RayTracer/tools/EmissionProfile.cpp
new file mode 100644
index 0000000..6ce0d7b
--- /dev/null
+++ b/RayTracer/tools/EmissionProfile.cpp
@@ -0,0 +1,101 @@
+#include "EmissionProfile.h"
+
+#include <math.h>
+
+#include <algorithm>
+#include <numeric>
+
+#include "../tools/Random.h"
+
+namespace util {
+
+EmissionProfile::EmissionProfile(const std::shared_ptr<util::Sampler>& emission,
+ float intensity)
+ : emission(emission),
+ uniform(true),
+ cdf(),
+ intensity(intensity),
+ normalizer(0.0f),
+ distribution(std::nullopt){};
+EmissionProfile::EmissionProfile(const std::shared_ptr<util::Sampler>& emission,
+ const Image& distribution, float intensity)
+ : emission(emission),
+ uniform(false),
+ intensity(intensity),
+ distribution(std::make_optional(distribution)) {
+ // vec: a vector with texel and grey value
+ std::vector<std::pair<std::pair<float, float>, float>> vec;
+ for (int w = 0; w <= distribution.width; w++) {
+ for (int h = 0; h <= distribution.height; h++) {
+ auto xyz = distribution[{w, h}];
+ float grey = 0.299f * xyz[0] + 0.587f * xyz[1] + 0.114f * xyz[2];
+ vec.push_back({{(float)w / (float)distribution.width,
+ (float)h / (float)distribution.height},
+ grey});
+ }
+ }
+ // Sort the value from biggest to smallest v
+ std::sort(vec.begin(), vec.end(),
+ [](std::pair<std::pair<float, float>, float> a,
+ std::pair<std::pair<float, float>, float> b) {
+ return a.second > b.second;
+ });
+ // Build cdf
+ cdf = {};
+ float cumm = 0;
+ for (auto x : vec) {
+ cumm += x.second;
+ // std::cout << cumm << std::endl;
+ cdf.push_back({x.first, cumm});
+ }
+ // Transform cdf to cap at 1
+ for (int i = 0; i < cdf.size(); i++) {
+ cdf[i].second = cdf[i].second / cumm;
+ }
+ // Normalizer
+ normalizer = (distribution.width * distribution.height) / cumm;
+};
+
+std::pair<float, float> EmissionProfile::sample() const {
+ if (uniform) {
+ return {(float)util::dis0to1(util::gen),
+ (float)util::dis0to1(util::gen)};
+ } else {
+ auto s = dis0to1(gen);
+ auto res = binary_search(s);
+ return res.first;
+ }
+};
+util::Vec3 EmissionProfile::color(float x, float y) const {
+ return emission->color(x, y);
+}
+std::optional<float> EmissionProfile::pdf(float x, float y) const {
+ if (uniform) return std::nullopt;
+ auto xyz = distribution->color(x, y);
+
+ return std::make_optional<float>(
+ (0.299f * xyz[0] + 0.587f * xyz[1] + 0.114f * xyz[2]) * normalizer);
+}
+
+std::pair<std::pair<float, float>, float> EmissionProfile::binary_search(
+ float target, int start, int end) const {
+ int mid;
+ if (end == -1) end = cdf.size();
+ while (start <= end) {
+ mid = (start + end) / 2;
+ if (cdf[mid].second <= target)
+ start = mid + 1;
+ else
+ end = mid - 1;
+ }
+ return cdf[mid];
+}
+// Not used
+std::pair<std::pair<float, float>, float> EmissionProfile::exponential_search(
+ float target) const {
+ if (cdf[0].second >= target) return cdf[0];
+ int start = 1;
+ while (start < cdf.size() && cdf[start].second <= target) start = 2 * start;
+ return binary_search(target, start / 2, std::min<int>(start, cdf.size()));
+}
+} // namespace util
\ No newline at end of file
diff --git a/RayTracer/tools/EmissionProfile.h b/RayTracer/tools/EmissionProfile.h
new file mode 100644
index 0000000..bdd74a1
--- /dev/null
+++ b/RayTracer/tools/EmissionProfile.h
@@ -0,0 +1,36 @@
+#pragma once
+
+#include <optional>
+
+#include "../sampling/Image.h"
+#include "../sampling/Sampler.h"
+
+namespace util {
+class EmissionProfile : public Sampler {
+ public:
+ // Uniform distribution constructor
+ EmissionProfile(const std::shared_ptr<util::Sampler>& emission,
+ float intensity = 1);
+ // Image distribution constructor
+ EmissionProfile(const std::shared_ptr<util::Sampler>& emission,
+ const Image& distribution, float intensity = 1);
+ // Returns a texels based on distribution
+ std::pair<float, float> sample() const;
+ util::Vec3 color(float x, float y) const override;
+ std::optional<float> pdf(float x, float y) const;
+
+ private:
+ std::shared_ptr<util::Sampler> emission;
+ std::optional<Image> distribution;
+ std::vector<std::pair<std::pair<float, float>, float>> cdf;
+ std::pair<std::pair<float, float>, float> binary_search(float target,
+ int start = 0,
+ int end = -1) const;
+ std::pair<std::pair<float, float>, float> exponential_search(
+ float target) const;
+ bool uniform;
+ float intensity;
+ float normalizer;
+};
+
+} // namespace util
\ No newline at end of file
--
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