feat: CSM 级联阴影（3 级联 × 1024²，实用分割 + 纹素对齐）

- SceneRenderer::ComputeCascades：相机视锥实用分割（λ=0.6）→ 反投影
  取切片角点 → 光空间 AABB 拟合 → 纹素对齐（消除相机移动时阴影边缘
  闪烁）→ [0,1] 深度重映射
- Shadow pass 单 pass 渲 3 个 region，每级联 push 各自光空间 VP
- Forward：UBO lightSpace[3]+cascadeSplits（视图深度选级联），Set2
  三张级联图按 binding 0/1/2 采样；vertex 输出 fragViewDepth
- 光源视锥剔除用最远级联（覆盖全阴影范围）；双视锥独立剔除铁律保留
- 旧单张 2048 全场景图退役；近处级联分辨率 ~128px/unit（约 2× 提升）
- 编译零错误、validation 零警告、8 秒冒烟通过（10 pass 全活跃）

Engine/include/Engine/Renderer/Passes/ForwardPass.h

@@ -19,10 +19,11 @@ namespace Engine::Passes {
     public:
         ForwardPass(SceneGpu& gpu, FrameSceneData& frame,
                     RG::TextureHandle hdrColor, RG::TextureHandle velocity,
-                    RG::TextureHandle depth, RG::TextureHandle shadowMap)
+                    RG::TextureHandle depth,
+                    const std::array<RG::TextureHandle, kMaxCascades>& shadowMaps)
             : m_Gpu(gpu), m_Frame(frame),
               m_HDRColor(hdrColor), m_Velocity(velocity),
-              m_Depth(depth), m_ShadowMap(shadowMap) {}
+              m_Depth(depth), m_ShadowMaps(shadowMaps) {}
 
         void Register(RG::RenderGraph& rg) override;
 
@@ -32,7 +33,7 @@ namespace Engine::Passes {
         RG::TextureHandle m_HDRColor;
         RG::TextureHandle m_Velocity;   // TAA 运动向量（第二颜色附件）
         RG::TextureHandle m_Depth;
-        RG::TextureHandle m_ShadowMap;
+        std::array<RG::TextureHandle, kMaxCascades> m_ShadowMaps;
     };
 
 } // namespace Engine::Passes

Engine/include/Engine/Renderer/Passes/SceneGpu.h

@@ -12,8 +12,10 @@
 #define HELLOVULKAN_SCENEGPU_H
 
 #include <Engine/Core/FrameContext.h>
+#include <Engine/Renderer/SceneTypes.h>
 #include <Engine/RenderGraph/RenderGraph.h>
 #include <vulkan/vulkan.hpp>
+#include <array>
 #include <vector>
 
 namespace Engine {
@@ -39,7 +41,7 @@ namespace Engine {
             // ---- set 布局（shader 契约，改绑定必须同步 shaders/）----
             vk::DescriptorSetLayout uboSetLayout;      // Set0 = {UBO, ObjectBuffer, PrevObjectBuffer}
             vk::DescriptorSetLayout textureSetLayout;  // Set1 = {albedo}
-            vk::DescriptorSetLayout shadowSetLayout;   // Set2 = {shadow map}
+            vk::DescriptorSetLayout shadowSetLayout;   // Set2 = {级联 0/1/2 阴影图}
             vk::PipelineLayout forwardLayout;          // 3 sets，无 push（GPUDriven 经 SSBO）
             vk::PipelineLayout shadowLayout;           // Set0，push = lightVP 64B
 
@@ -55,7 +57,8 @@ namespace Engine {
             vk::ShaderEXT shadowVert{}, shadowFrag{};
 
             // RG 重编译后重绑阴影图（物理镜像按槽位各一份）
-            void BindShadowMap(RG::RenderGraph& rg, RG::TextureHandle shadowMap);
+            void BindShadowMaps(RG::RenderGraph& rg,
+                                const std::array<RG::TextureHandle, kMaxCascades>& maps);
 
         private:
             Device& m_Device;

Engine/include/Engine/Renderer/Passes/ShadowPass.h

@@ -1,8 +1,9 @@
 //
 // Created by atdunbg on 2026/9/23.
 //
-// ShadowPass：光源视角写深度。GPUDriven batch 消费光源视锥剔除结果
-// （FrameSceneData::shadowView——相机外实体仍投影子）。
+// ShadowPass：CSM 级联阴影。单 pass 渲 kMaxCascades 个 region，
+// 每级联独立光源 VP（FrameSceneData::lightSpace[c]，SceneRenderer 拟合），
+// 消费光源视锥剔除结果（FrameSceneData::shadowView——相机外实体仍投影子）。
 //
 
 #ifndef HELLOVULKAN_SHADOWPASS_H
@@ -11,13 +12,15 @@
 #include <Engine/Renderer/Passes/RenderPass.h>
 #include <Engine/Renderer/Passes/SceneGpu.h>
 #include <Engine/Renderer/SceneTypes.h>
+#include <array>
 
 namespace Engine::Passes {
 
     class ShadowPass final : public RenderPass {
     public:
-        ShadowPass(SceneGpu& gpu, FrameSceneData& frame, RG::TextureHandle shadowMap)
-            : m_Gpu(gpu), m_Frame(frame), m_ShadowMap(shadowMap) {}
+        ShadowPass(SceneGpu& gpu, FrameSceneData& frame,
+                   const std::array<RG::TextureHandle, kMaxCascades>& shadowMaps)
+            : m_Gpu(gpu), m_Frame(frame), m_ShadowMaps(shadowMaps) {}
 
         void Register(RG::RenderGraph& rg) override;
         void OnTargetsRebuilt(RG::RenderGraph& rg) override;
@@ -25,7 +28,7 @@ namespace Engine::Passes {
     private:
         SceneGpu& m_Gpu;
         FrameSceneData& m_Frame;
-        RG::TextureHandle m_ShadowMap;
+        std::array<RG::TextureHandle, kMaxCascades> m_ShadowMaps;
     };
 
 } // namespace Engine::Passes