From 040497887ccf97738c48c5f6cc432f27bbb60dc9 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 24 Sep 2020 19:06:33 +0300
Subject: [PATCH] Implement fractal perlin noise

---
 libs/pcg/include/psemek/pcg/perlin.hpp | 22 +++++++++
 libs/pcg/source/perlin.cpp             | 64 ++++++++++++++++++++++++++
 todo.md                                |  1 +
 3 files changed, 87 insertions(+)

diff --git a/libs/pcg/include/psemek/pcg/perlin.hpp b/libs/pcg/include/psemek/pcg/perlin.hpp
index 716b9b52..57c940da 100644
--- a/libs/pcg/include/psemek/pcg/perlin.hpp
+++ b/libs/pcg/include/psemek/pcg/perlin.hpp
@@ -4,6 +4,8 @@
 #include <psemek/geom/vector.hpp>
 #include <psemek/pcg/seamless.hpp>
 
+#include <vector>
+
 namespace psemek::pcg
 {
 
@@ -37,4 +39,24 @@ namespace psemek::pcg
 		gfx::basic_pixmap<geom::vector<float, 2>> grad_map_;
 	};
 
+	struct fractal_perlin
+	{
+		fractal_perlin() = default;
+		fractal_perlin(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> grad_maps);
+		fractal_perlin(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> grad_maps, std::vector<float> weights);
+		fractal_perlin(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> const & grad_maps, seamless_tag);
+		fractal_perlin(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> const & grad_maps, std::vector<float> weights, seamless_tag);
+		fractal_perlin(fractal_perlin &&) = default;
+
+		fractal_perlin & operator = (fractal_perlin &&) = default;
+
+		// x \in [0.0 .. 1.0]
+		// y \in [0.0 .. 1.0]
+		float operator()(float x, float y) const;
+
+	private:
+		std::vector<perlin> octaves_;
+		std::vector<float> weights_;
+	};
+
 }
diff --git a/libs/pcg/source/perlin.cpp b/libs/pcg/source/perlin.cpp
index 4ebcd909..8aac4cb2 100644
--- a/libs/pcg/source/perlin.cpp
+++ b/libs/pcg/source/perlin.cpp
@@ -64,4 +64,68 @@ namespace psemek::pcg
 		return 0.5f + v * 0.5f;
 	}
 
+	static std::vector<float> estimate_weights(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> const & grad_maps)
+	{
+		std::vector<float> weights(grad_maps.size());
+
+		float sum = 0.f;
+		for (std::size_t i = 0; i < grad_maps.size(); ++i)
+		{
+			auto const & m = grad_maps[i];
+			weights[i] = 1.f / std::sqrt(m.width() * m.width() + m.height() * m.height());
+			sum += weights[i];
+		}
+
+		for (std::size_t i = 0; i < grad_maps.size(); ++i)
+			weights[i] /= sum;
+
+		return weights;
+	}
+
+	fractal_perlin::fractal_perlin(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> grad_maps)
+	{
+		weights_ = estimate_weights(grad_maps);
+
+		octaves_.resize(grad_maps.size());
+		for (std::size_t i = 0; i < grad_maps.size(); ++i)
+			octaves_[i] = perlin(std::move(grad_maps[i]));
+	}
+
+	fractal_perlin::fractal_perlin(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> grad_maps, std::vector<float> weights)
+		: weights_{std::move(weights)}
+	{
+		assert(weights_.size() == grad_maps.size());
+
+		octaves_.resize(grad_maps.size());
+		for (std::size_t i = 0; i < grad_maps.size(); ++i)
+			octaves_[i] = perlin(std::move(grad_maps[i]));
+	}
+
+	fractal_perlin::fractal_perlin(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> const & grad_maps, seamless_tag)
+	{
+		weights_ = estimate_weights(grad_maps);
+
+		octaves_.resize(grad_maps.size());
+		for (std::size_t i = 0; i < grad_maps.size(); ++i)
+			octaves_[i] = perlin(grad_maps[i], seamless);
+	}
+
+	fractal_perlin::fractal_perlin(std::vector<gfx::basic_pixmap<geom::vector<float, 2>>> const & grad_maps, std::vector<float> weights, seamless_tag)
+		: weights_{std::move(weights)}
+	{
+		assert(weights_.size() == grad_maps.size());
+
+		octaves_.resize(grad_maps.size());
+		for (std::size_t i = 0; i < grad_maps.size(); ++i)
+			octaves_[i] = perlin(grad_maps[i], seamless);
+	}
+
+	float fractal_perlin::operator()(float x, float y) const
+	{
+		float v = 0.f;
+		for (std::size_t i = 0; i < octaves_.size(); ++i)
+			v += weights_[i] * octaves_[i](x, y);
+		return v;
+	}
+
 }
diff --git a/todo.md b/todo.md
index 4f5fb661..579cd1b0 100644
--- a/todo.md
+++ b/todo.md
@@ -7,3 +7,4 @@
 * gfx: design & implement simple rendering pipelines
 * pcg: add clean Generator, Sampler & Pixmap processor concepts, uniformize interfaces, be type & dimension agnostic when possible
 * pcg: add more vector & point distributions
+* pcg: make template fractal generator, replace fractal_perlin with it