ADD: Lighting modifier and IBL probe

src/core/assets/ibl_manager.h

@@ -3,6 +3,8 @@
 #include <core/types.h>
 #include <string>
 
+class TextureCache;
+
 class EngineContext;
 
 struct IBLPaths
@@ -10,6 +12,9 @@ struct IBLPaths
     std::string specularCube; // .ktx2 (GPU-ready BC6H or R16G16B16A16)
     std::string diffuseCube; // .ktx2
     std::string brdfLut2D; // .ktx2 (BC5 RG UNORM or similar)
+    // Optional separate background environment map (2D equirect .ktx2).
+    // When empty, the IBL system falls back to using specularCube for the background.
+    std::string background2D;
 };
 
 class IBLManager
@@ -17,6 +22,8 @@ class IBLManager
 public:
     void init(EngineContext *ctx) { _ctx = ctx; }
 
+    void set_texture_cache(TextureCache *cache) { _cache = cache; }
+
     // Load all three textures. Returns true when specular+diffuse (and optional LUT) are resident.
     bool load(const IBLPaths &paths);
 
@@ -28,6 +35,9 @@ public:
     AllocatedImage specular() const { return _spec; }
     AllocatedImage diffuse() const { return _diff; }
     AllocatedImage brdf() const { return _brdf; }
+    // Background environment texture used by the background pass.
+    // May alias specular() when a dedicated background is not provided.
+    AllocatedImage background() const { return _background; }
     AllocatedBuffer shBuffer() const { return _shBuffer; }
     bool hasSH() const { return _shBuffer.buffer != VK_NULL_HANDLE; }
 
@@ -39,9 +49,14 @@ public:
 
 private:
     EngineContext *_ctx{nullptr};
+    TextureCache *_cache{nullptr};
     AllocatedImage _spec{};
     AllocatedImage _diff{};
     AllocatedImage _brdf{};
+    AllocatedImage _background{};
     VkDescriptorSetLayout _iblSetLayout = VK_NULL_HANDLE;
     AllocatedBuffer _shBuffer{}; // 9*vec4 coefficients (RGB in .xyz)
+
+    // Destroy current GPU images/SH buffer but keep descriptor layout alive.
+    void destroy_images_and_sh();
 };