# OpenGLVertexArray

OpenGL 顶点数组对象 (VAO) 封装。

## 头文件

```cpp
#include <XCEngine/RHI/OpenGL/OpenGLVertexArray.h>
```

## VertexAttribute

```cpp
struct VertexAttribute {
    unsigned int index;    // 属性索引 (layout location)
    int count;             // 组件数量 (1-4)
    unsigned int type;     // GL 类型 (GL_FLOAT, etc.)
    bool normalized;       // 是否归一化
    size_t stride;         // 顶点步长
    size_t offset;         // 属性偏移
};
```

## 公共成员函数

#### `OpenGLVertexArray()`

#### `~OpenGLVertexArray()`

#### `bool Initialize()`

#### `void AddVertexBuffer(unsigned int buffer, const VertexAttribute& attribute)`

#### `void SetIndexBuffer(unsigned int buffer, unsigned int type)`

#### `void Shutdown()`

#### `void Bind() const`

#### `void Unbind() const`

#### `unsigned int GetID() const`

#### `unsigned int GetIndexBuffer() const`

#### `unsigned int GetIndexCount() const`

## 内部成员

| 成员 | 类型 | 描述 |
|------|------|------|
| `m_vao` | `unsigned int` | GL VAO ID |
| `m_indexBuffer` | `unsigned int` | 索引缓冲区 |
| `m_indexCount` | `unsigned int` | 索引数量 |
| `m_vertexBufferCount` | `int` | 顶点缓冲区数量 |

## 使用示例

```cpp
OpenGLVertexArray vao;
vao.Initialize();

// Position attribute
VertexAttribute pos;
pos.index = 0;
pos.count = 3;
pos.type = GL_FLOAT;
pos.normalized = false;
pos.stride = sizeof(Vertex);
pos.offset = 0;
vao.AddVertexBuffer(vb.GetID(), pos);

// UV attribute
VertexAttribute uv;
uv.index = 1;
uv.count = 2;
uv.type = GL_FLOAT;
uv.normalized = false;
uv.stride = sizeof(Vertex);
uv.offset = sizeof(float) * 3;
vao.AddVertexBuffer(vb.GetID(), uv);

// Index buffer
vao.SetIndexBuffer(ib.GetID(), GL_UNSIGNED_SHORT);

vao.Bind();
glDrawElements(GL_TRIANGLES, vao.GetIndexCount(), GL_UNSIGNED_SHORT, 0);
```