feat(RHI): 实现 RHISampler 抽象基类

- 新增 RHISampler 抽象基类
- D3D12Sampler 继承 RHISampler
- OpenGLSampler 继承 RHISampler，使用 OpenGLSamplerDesc
- 文档更新 RHISampler 差异处理策略

docs/RHI抽象层设计与实现.md

@@ -491,7 +491,55 @@ public:
    - OpenGL：glUseProgram
     - 解决：基类提供 Bind/Unbind 接口
 
-### 5.8 根签名 vs OpenGL 资源绑定
+### 5.8 采样器（RHISampler）抽象设计
+
+#### 5.8.1 设计理念对应
+
+| 差异点 | 设计理念 | 处理方案 |
+|--------|---------|---------|
+| 初始化参数差异 | 求同存异 | 后端各自实现初始化 |
+| 句柄类型差异 | 底层逃逸 | 统一返回 void* |
+| 绑定方式 | 求同存异 | 基类提供 Bind/Unbind |
+
+#### 5.8.2 现有实现对比
+
+| 功能 | D3D12Sampler | OpenGLSampler |
+|------|--------------|---------------|
+| 初始化 | Initialize(device, desc) | Initialize(desc) |
+| 销毁 | Shutdown() | Shutdown() |
+| 绑定 | 通过 DescriptorHeap | Bind(unit) |
+| 句柄 | GetNativeHandle() | GetID() |
+
+#### 5.8.3 抽象接口定义
+
+```cpp
+class RHISampler {
+public:
+    virtual ~RHISampler() = default;
+
+    virtual void Shutdown() = 0;
+
+    virtual void Bind(unsigned int unit) = 0;
+    virtual void Unbind(unsigned int unit) = 0;
+
+    virtual void* GetNativeHandle() = 0;
+    virtual unsigned int GetID() = 0;
+};
+```
+
+#### 5.8.4 差异处理策略
+
+1. **初始化参数差异（求同存异）**
+   - D3D12：需要 device 参数
+   - OpenGL：不需要 device
+   - 解决：Device 的 CreateSampler() 统一接收 SamplerDesc，后端各自实现 Initialize()
+
+2. **句柄类型差异（底层逃逸）**
+   - D3D12：通过 DescriptorHeap 管理
+   - OpenGL：GLuint
+   - 解决：GetNativeHandle() 返回 void*
+
+### 5.9 根签名 vs OpenGL 资源绑定
 - **D3D12**：显式 `RootSignature` 定义资源绑定规则
 - **OpenGL**：隐式通过 `glUniformLocation`、`glBindTextureUnit` 绑定
 - **解决方案**：

engine/include/XCEngine/RHI/D3D12/D3D12Sampler.h

@@ -3,6 +3,7 @@
 #include <d3d12.h>
 #include <wrl/client.h>
 
+#include "../RHISampler.h"
 #include "D3D12Enum.h"
 
 using Microsoft::WRL::ComPtr;
@@ -10,17 +11,21 @@ using Microsoft::WRL::ComPtr;
 namespace XCEngine {
 namespace RHI {
 
-class D3D12Sampler {
+class D3D12Sampler : public RHISampler {
 public:
     D3D12Sampler();
-    ~D3D12Sampler();
+    ~D3D12Sampler() override;
 
     bool Initialize(ID3D12Device* device, const D3D12_SAMPLER_DESC& desc);
-    void Shutdown();
+    void Shutdown() override;
 
     D3D12_SAMPLER_DESC GetDesc() const { return m_desc; }
 
-    void* GetNativeHandle() const { return nullptr; }
+    void* GetNativeHandle() override { return nullptr; }
+    unsigned int GetID() override { return 0; }
+
+    void Bind(unsigned int unit) override { }
+    void Unbind(unsigned int unit) override { }
 
 private:
     D3D12_SAMPLER_DESC m_desc;

engine/include/XCEngine/RHI/OpenGL/OpenGLSampler.h

@@ -2,6 +2,9 @@
 
 #include <GLFW/glfw3.h>
 
+#include "../RHISampler.h"
+#include "../RHITypes.h"
+
 namespace XCEngine {
 namespace RHI {
 
@@ -26,7 +29,7 @@ enum class SamplerCompareMode {
     CompareToRef
 };
 
-struct SamplerDesc {
+struct OpenGLSamplerDesc {
     SamplerFilter minFilter = SamplerFilter::LinearMipmapLinear;
     SamplerFilter magFilter = SamplerFilter::Linear;
     SamplerWrapMode wrapS = SamplerWrapMode::Repeat;
@@ -39,22 +42,24 @@ struct SamplerDesc {
     float maxLod = 1000.0f;
 };
 
-class OpenGLSampler {
+class OpenGLSampler : public RHISampler {
 public:
     OpenGLSampler();
-    ~OpenGLSampler();
+    ~OpenGLSampler() override;
 
-    bool Initialize(const SamplerDesc& desc);
-    void Shutdown();
+    bool Initialize(const OpenGLSamplerDesc& desc);
+    void Shutdown() override;
 
-    void Bind(unsigned int unit);
-    void Unbind(unsigned int unit);
+    void Bind(unsigned int unit) override;
+    void Unbind(unsigned int unit) override;
 
     unsigned int GetID() const { return m_sampler; }
+    unsigned int GetID() override { return m_sampler; }
+    void* GetNativeHandle() override { return reinterpret_cast<void*>(static_cast<uintptr_t>(m_sampler)); }
 
 private:
     unsigned int m_sampler;
-    SamplerDesc m_desc;
+    OpenGLSamplerDesc m_desc;
 };
 
 } // namespace RHI

engine/include/XCEngine/RHI/RHISampler.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "RHITypes.h"
+#include "RHIEnums.h"
+
+namespace XCEngine {
+namespace RHI {
+
+class RHISampler {
+public:
+    virtual ~RHISampler() = default;
+
+    virtual void Shutdown() = 0;
+
+    virtual void Bind(unsigned int unit) = 0;
+    virtual void Unbind(unsigned int unit) = 0;
+
+    virtual void* GetNativeHandle() = 0;
+    virtual unsigned int GetID() = 0;
+};
+
+} // namespace RHI
+} // namespace XCEngine

engine/src/RHI/OpenGL/OpenGLSampler.cpp

@@ -34,7 +34,7 @@ OpenGLSampler::OpenGLSampler() : m_sampler(0) {
 OpenGLSampler::~OpenGLSampler() {
 }
 
-bool OpenGLSampler::Initialize(const SamplerDesc& desc) {
+bool OpenGLSampler::Initialize(const OpenGLSamplerDesc& desc) {
     m_desc = desc;
     glGenSamplers(1, &m_sampler);