翻译自DXSDK
将渲染目标数据从设备内存拷贝到系统内存。
HRESULT GetRenderTargetData(
[in] IDirect3DSurface9 *pRenderTarget,
[in] IDirect3DSurface9 *pDestSurface
);
pRenderTarget [in]
Pointer to an IDirect3DSurface9 object, representing a render target.
指向一个IDirect3DSurface9对象，代表一个渲染目标，源表面。
pDestSurface [in]
Pointer to an IDirect3DSurface9 object, representing a destination surface.
指向一个IDirect3DSurface9对象，代表一个目的表面。
注意：
The destination surface must be either an off-screen plain surface or a level of a texture (mipmap or cube texture) created with D3DPOOL_SYSTEMMEM.
目的表面的内存池类型需要是 D3DPOOL_SYSTEMMEM （系统内存）
The source surface must be a regular render target or a level of a render-target texture (mipmap or cube texture) created with POOL_DEFAULT.
源表面的内存池类型需要是POOL_DEFAULT
This method will fail if:
- The render target is multisampled.
源表面如果多重采样则拷贝失败。
- The source render target is a different size than the destination surface.
两个表面尺寸不一致拷贝失败。
- The source render target and destination surface formats do not match.
像素格式不一致拷贝失败。