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。

本文参考了这篇blog。