feat(renderer): add shadow mapping with PCF soft shadows

Introduce shadow mapping using a dedicated depth framebuffer and shader. The block fragment shader now performs percentage-closer filtering (PCF) with Poisson disk sampling and random rotation for soft shadows. The vertex shader outputs light-space coordinates. A new depth shader pair handles rendering from the light's perspective, discarding transparent fragments. The renderer sets up the light projection based on the camera position and sun direction, and applies the shadow factor to diffuse lighting. Day/night cycle can now be toggled off in the world server thread.

include/Cubed/camera.hpp

@@ -32,6 +32,7 @@ public:
     const glm::vec3& get_camera_pos() const;
 
     bool is_under_water() const;
+    glm::vec3 get_camera_front() const;
 };
 
 } // namespace Cubed

include/Cubed/gameplay/world.hpp

@@ -69,6 +69,7 @@ private:
     std::atomic<bool> m_is_rebuilding{false};
     std::atomic<bool> m_chunk_gen_finished{false};
     std::atomic<bool> m_could_gen{true};
+    std::atomic<bool> m_day_night_cycle{true};
     std::atomic<int> m_rendering_distance{24};
     std::atomic<float> m_chunk_gen_fraction{0.0f};
 

include/Cubed/renderer.hpp

@@ -39,7 +39,8 @@ private:
     static constexpr float NEAR_PLANE = 0.1f;
     static constexpr float SUN_SIZE = 50.0f;
     static constexpr float MOON_SIZE = 50.0f;
-
+    static constexpr float DEPTH_MAP_WIDTH = 2048.0f;
+    static constexpr float DEPTH_MAP_HEIGHT = 2048.0f;
     float m_ambient_strength = 0.1f;
 
     const Camera& m_camera;
@@ -74,6 +75,10 @@ private:
     GLuint m_accum_texture = 0;
     GLuint m_reveal_texture = 0;
     GLuint m_oit_depth_render_buffer = 0;
+
+    GLuint m_depth_map_fbo = 0;
+    GLuint m_depth_map_texture = 0;
+
     GLuint m_quad_vbo = 0;
 
     glm::mat4 m_ui_proj;