From 90ece36fd5547f0d8c986fa5bd9b1e32854ebeae Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sun, 27 Sep 2020 16:44:13 +0300
Subject: [PATCH] Add uniform distribution inside a ball

---
 .../psemek/pcg/random/uniform_ball.hpp        | 61 +++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 libs/pcg/include/psemek/pcg/random/uniform_ball.hpp

diff --git a/libs/pcg/include/psemek/pcg/random/uniform_ball.hpp b/libs/pcg/include/psemek/pcg/random/uniform_ball.hpp
new file mode 100644
index 00000000..5698a1ba
--- /dev/null
+++ b/libs/pcg/include/psemek/pcg/random/uniform_ball.hpp
@@ -0,0 +1,61 @@
+#pragma once
+
+#include <psemek/pcg/random/uniform_sphere.hpp>
+#include <psemek/pcg/random/uniform_real.hpp>
+
+namespace psemek::pcg
+{
+
+	template <typename T, std::size_t N>
+	struct uniform_ball_vector_distribution
+	{
+		using result_type = geom::vector<T, N>;
+
+		uniform_ball_vector_distribution(T r = T{1})
+			: sphere_d_{r}
+		{}
+
+		uniform_ball_vector_distribution(uniform_ball_vector_distribution const &) = default;
+
+		template <typename RNG>
+		auto operator()(RNG && rng)
+		{
+			result_type v = sphere_d_(rng);
+			auto r = uniform_real_distribution<T>{}(rng);
+			return v * std::pow(r, T{1} / N);
+		}
+
+		T radius() const { return sphere_d_.radius(); }
+
+	private:
+		uniform_sphere_vector_distribution<T, N> sphere_d_;
+	};
+
+	template <typename T, std::size_t N>
+	struct uniform_ball_point_distribution
+	{
+		using result_type = geom::vector<T, N>;
+
+		uniform_ball_point_distribution(result_type origin, T r = T{1})
+			: origin_{origin}
+			, vector_d_{r}
+		{}
+
+		uniform_ball_point_distribution(uniform_ball_point_distribution const &) = default;
+
+		template <typename RNG>
+		auto operator()(RNG && rng)
+		{
+			return origin_ + vector_d_(rng);
+		}
+
+		result_type origin() const { return origin_; }
+
+		T radius() const { return vector_d_.radius(); }
+
+	private:
+		result_type origin_;
+		uniform_ball_vector_distribution<T, N> vector_d_;
+	};
+
+}