Reorganize source files into logical subdirectories

Co-authored-by: Hirek193 <23196899+Hirek193@users.noreply.github.com>

rendering/openglprecipitation.h

@@ -0,0 +1,39 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma	once
+
+#include "Texture.h"
+
+class opengl_precipitation {
+
+public:
+// constructors
+    opengl_precipitation() = default;
+// destructor
+	~opengl_precipitation();
+// methods
+    void
+        update();
+	void
+        render( GLint const Textureunit );
+
+private:
+// methods
+    void create( int const Tesselation );
+// members
+    std::vector<glm::vec3> m_vertices;
+    std::vector<glm::vec2> m_uvs;
+    std::vector<std::uint16_t> m_indices;
+    GLuint m_vertexbuffer { (GLuint)-1 };
+    GLuint m_uvbuffer { (GLuint)-1 };
+    GLuint m_indexbuffer { (GLuint)-1 };
+    texture_handle m_texture { null_handle };
+    float m_overcast { -1.f }; // cached overcast level, difference from current state triggers texture update
+};