# OpenGLRenderTargetView

OpenGL 渲染目标视图实现，使用 framebuffer object (FBO)。

## 头文件

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

## 枚举

### RenderTargetType

| 值 | 描述 |
|----|------|
| `Texture2D` | 2D 纹理 |
| `Texture2DArray` | 2D 纹理数组 |
| `Texture3D` | 3D 纹理 |
| `TextureCube` | 立方体贴图 |
| `TextureCubeArray` | 立方体贴图数组 |

## OpenGLRenderTargetViewDesc

```cpp
struct OpenGLRenderTargetViewDesc {
    RenderTargetType type = RenderTargetType::Texture2D;
    int mipLevel = 0;
    int baseArraySlice = 0;
    int arraySize = 1;
    int layer = 0;
    uint32_t format = 0;
};
```

## 公共成员函数

#### `OpenGLRenderTargetView()`

#### `~OpenGLRenderTargetView()`

#### `bool Initialize(unsigned int texture, const OpenGLRenderTargetViewDesc& desc)`

#### `bool Initialize(unsigned int texture, int mipLevel = 0)`

#### `bool InitializeCubemap(unsigned int cubemap, int face, int mipLevel = 0)`

#### `void Shutdown()`

#### `void Bind(unsigned int slot = 0)`

#### `void Bind(unsigned int count, const unsigned int* framebuffers, const int* drawBuffers)`

#### `void Unbind()`

#### `void Clear(float r, float g, float b, float a)`

#### `void Clear(float r, float g, float b, float a, float depth, uint8_t stencil)`

#### `unsigned int GetFramebuffer() const`

#### `unsigned int GetTexture() const`

#### `int GetMipLevel() const`

#### `int GetWidth() const`

#### `int GetHeight() const`

#### `static void BindFramebuffer(unsigned int framebuffer)`

#### `static void UnbindFramebuffer()`

## 内部成员

| 成员 | 类型 | 描述 |
|------|------|------|
| `m_texture` | `unsigned int` | GL texture ID |
| `m_framebuffer` | `unsigned int` | GL framebuffer ID |
| `m_mipLevel` | `int` | Mip 级别 |
| `m_width/height` | `int` | 尺寸 |
| `m_type` | `RenderTargetType` | 类型 |
| `m_framebuffers` | `vector<unsigned int>` | 额外 framebuffer 列表 |

## 使用示例

```cpp
// Create framebuffer with color attachment
OpenGLRenderTargetView rtv;
rtv.Initialize(texture.GetID());

rtv.Bind();
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
rtv.Unbind();

// MRT
OpenGLRenderTargetView rtvs[2];
rtvs[0].Initialize(texture0.GetID());
rtvs[1].Initialize(texture1.GetID());

unsigned int fbs[] = { rtvs[0].GetFramebuffer(), rtvs[1].GetFramebuffer() };
int draws[] = { 0, 1 };
rtvs[0].Bind(2, fbs, draws);
glClear(GL_COLOR_BUFFER_BIT);
```