Add 3d mono audio effect

libs/audio/CMakeLists.txt

@@ -5,4 +5,4 @@ file(GLOB_RECURSE PSEMEK_AUDIO_SOURCES RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "s
 
 psemek_add_library(psemek-audio ${PSEMEK_AUDIO_HEADERS} ${PSEMEK_AUDIO_SOURCES})
 target_include_directories(psemek-audio PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/include")
-target_link_libraries(psemek-audio PUBLIC psemek-sdl2 psemek-util psemek-log SDL2_mixer)
+target_link_libraries(psemek-audio PUBLIC psemek-sdl2 psemek-geom psemek-util psemek-log SDL2_mixer)

libs/audio/include/psemek/audio/3d.hpp

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <psemek/audio/effect.hpp>
+#include <psemek/geom/point.hpp>
+
+#include <memory>
+#include <optional>
+#include <mutex>
+
+namespace psemek::audio
+{
+
+	struct listener_3d_mono
+	{
+		void set_position(geom::point<float, 3> const & position);
+
+		virtual std::shared_ptr<effect> make_effect(geom::point<float, 3> const & position, float distance_factor);
+
+	private:
+		geom::point<float, 3> position_;
+		std::mutex position_mutex_;
+	};
+
+}

libs/audio/source/3d.cpp

@@ -0,0 +1,68 @@
+#include <psemek/audio/3d.hpp>
+#include <psemek/util/not_implemented.hpp>
+
+#include <optional>
+#include <mutex>
+
+namespace psemek::audio
+{
+
+	namespace
+	{
+
+		struct mono_impl
+			: effect
+		{
+			mono_impl(geom::point<float, 3> const & source_position, geom::point<float, 3> & target_position, std::mutex & target_position_mutex, float distance_factor)
+				: source_position_(source_position)
+				, target_position_(target_position)
+				, cached_target_position_(target_position)
+				, target_position_mutex_(target_position_mutex)
+				, distance_factor_(distance_factor)
+			{}
+
+			std::string_view name() const override
+			{
+				return "mono_3d";
+			}
+
+			void init(int, int) override
+			{ }
+
+			void operator()(sample * data, std::size_t count) override
+			{
+				{
+					std::unique_lock lock{target_position_mutex_, std::try_to_lock};
+					if (lock.owns_lock())
+						cached_target_position_ = target_position_;
+				}
+
+				float distance = geom::distance(cached_target_position_, source_position_) / distance_factor_;
+				float factor = std::min(1.f, 1.f / (1.f + distance * distance));
+
+				for (std::size_t i = 0; i < count; ++i)
+					data[i] = pack(unpack(data[i]) * factor);
+			}
+
+		private:
+			geom::point<float, 3> source_position_;
+			geom::point<float, 3> & target_position_;
+			geom::point<float, 3> cached_target_position_;
+			std::mutex & target_position_mutex_;
+			float distance_factor_;
+		};
+
+	}
+
+	void listener_3d_mono::set_position(geom::point<float, 3> const & position)
+	{
+		std::lock_guard lock{position_mutex_};
+		position_ = position;
+	}
+
+	std::shared_ptr<effect> listener_3d_mono::make_effect(const geom::point<float, 3> &position, float distance_factor)
+	{
+		return std::make_shared<mono_impl>(position, position_, position_mutex_, distance_factor);
+	}
+
+}