有时候，我们需要查看depth/stencil buffer的内容，比如上一章中，我们要查看stencil buffer，看看我们设置的stencil值是否起作用，这时就要输出depth/stencil buffer内容，但这些内容在gpu中，我们并不能直接查看，需要通过纹理copy，资源映射的方式，拷贝到system memory中才可以直接查看。

     下面是输出depth/stencil buffer的代码，最终结果被输出到一个csv文件中，便于用excel 查看。该函数我加在了D3DClass类中：

    bool D3DClass::SaveDepthStencilBuffer()
        {
           D3D11_TEXTURE2D_DESC dsDesc, destTexDesc;
           ID3D11Texture2D*    destTex;
            HRESULT result;

           if(m_depthStencilBuffer)
               {
               m_depthStencilBuffer->GetDesc(&dsDesc);
              // 使目的和源的描述一致
                memcpy(&destTexDesc,&dsDesc,sizeof(destTexDesc));
               destTexDesc.Usage            = D3D11_USAGE_STAGING;
               destTexDesc.BindFlags        = 0;
               destTexDesc.CPUAccessFlags    = D3D11_CPU_ACCESS_READ;   
               result = m_device->CreateTexture2D(&destTexDesc, 0, &destTex);
               if(FAILED(result))
                   {
                   HR(result);
                   return false;
                   }

               //depthBufferDesc.Format = DXGI_FORMAT_D24_UNORM_S8_UINT;
              
               m_deviceContext->CopyResource(destTex, m_depthStencilBuffer);

               D3D11_MAPPED_SUBRESOURCE mappedResource;

               result = m_deviceContext->Map(destTex, 0, D3D11_MAP_READ, 0, &mappedResource);
               if(FAILED(result))
                   {
                   return false;
                   }

               FILE *fp = fopen("depth-stencil.csv","w");

               const UINT WIDTH = destTexDesc.Width ;
               const UINT HEIGHT = destTexDesc.Height;
               //映射为32位的dword
               DWORD* pTexels = (DWORD*)mappedResource.pData;
               for( UINT row = 0; row < HEIGHT; row++ )
                   {
                   UINT rowStart = row * mappedResource.RowPitch/sizeof(pTexels[0]);
                   for( UINT col = 0; col < WIDTH; col++ )
                       {
                       fprintf(fp,"%08x,",pTexels[rowStart + col]);
                       }
                   fprintf(fp,"\n");
                   }

               fclose(fp);
               m_deviceContext->Unmap(destTex, 0);
               }
               return true;
       
        }

在GraphicClass类的Render函数中，调用该函数，我们就可以得到depth/stencil buffer的内容了。

本文参考了http://www.cppblog.com/GameAcademe/articles/DirectX11.html这篇blog。