DirectX9 SDK Samples(20) HDRDemo Sample(2)

接下来进入第二部分，Bloom，SDK里称为post-processing effect。代码所在文件为PostProcess.cpp。

LPDIRECT3DTEXTURE9 g_pBrightPassTex = NULL;             // The results of performing a bright pass on the original HDR imageryLPDIRECT3DTEXTURE9 g_pDownSampledTex = NULL;             // The scaled down version of the bright pass resultsLPDIRECT3DTEXTURE9 g_pBloomHorizontal = NULL;             // The horizontally blurred version of the downsampled textureLPDIRECT3DTEXTURE9 g_pBloomVertical = NULL;             // The vertically blurred version of the horizontal blurD3DFORMAT g_fmtHDR = D3DFMT_UNKNOWN;   // What HDR (128 or 64) format is being usedLPDIRECT3DPIXELSHADER9 g_pBrightPassPS = NULL;             // Represents the bright pass processingLPD3DXCONSTANTTABLE g_pBrightPassConstants = NULL;LPDIRECT3DPIXELSHADER9 g_pDownSamplePS = NULL;             // Represents the downsampling processingLPD3DXCONSTANTTABLE g_pDownSampleConstants = NULL;LPDIRECT3DPIXELSHADER9 g_pHBloomPS = NULL;             // Performs the first stage of the bloom renderingLPD3DXCONSTANTTABLE g_pHBloomConstants = NULL;LPDIRECT3DPIXELSHADER9 g_pVBloomPS = NULL;             // Performs the second stage of the bloom renderingLPD3DXCONSTANTTABLE g_pVBloomConstants = NULL;

从这些变量我们可以得知：一共需要4个纹理，对应4个像素着色器。

CreateResource就不说了，无非是创建纹理和载入着色器。

//--------------------------------------------------------------------------------------//  PerformPostProcessing( )////      DESC://          This is the core function for this module - it takes the raw HDR image//          generated by the 'HDRScene' component and puts it through 4 post//          processing stages - to end up with a bloom effect on the over-exposed//          (HDR) parts of the image.

    LPDIRECT3DTEXTURE9 pHDRSource = NULL;    HDRScene::GetOutputTexture( &pHDRSource );    LPDIRECT3DSURFACE9 pBrightPassSurf = NULL;    PostProcess::g_pBrightPassTex->GetSurfaceLevel( 0, &pBrightPassSurf );

    pDevice->SetRenderTarget( 0, pBrightPassSurf );         // Configure the output of this stage    pDevice->SetTexture( 0, pHDRSource );                   // Configure the input..    pDevice->SetPixelShader( PostProcess::g_pBrightPassPS );    PostProcess::g_pBrightPassConstants->SetFloat( pDevice, "fBrightPassThreshold", PostProcess::g_BrightThreshold );    // We need to compute the sampling offsets used for this pass.    // A 2x2 sampling pattern is used, so we need to generate 4 offsets    D3DXVECTOR4 offsets[4];    // Find the dimensions for the source data    D3DSURFACE_DESC srcDesc;    pHDRSource->GetLevelDesc( 0, &srcDesc );    // Because the source and destination are NOT the same sizes, we    // need to provide offsets to correctly map between them.    float sU = ( 1.0f / static_cast< float >( srcDesc.Width ) );    float sV = ( 1.0f / static_cast< float >( srcDesc.Height ) );    // The last two components (z,w) are unused. This makes for simpler code, but if    // constant-storage is limited then it is possible to pack 4 offsets into 2 float4's    offsets[0] = D3DXVECTOR4( -0.5f * sU, 0.5f * sV, 0.0f, 0.0f );//省略其他offset    PostProcess::g_pBrightPassConstants->SetVectorArray( pDevice, "tcDownSampleOffsets", offsets, 4 );    RenderToTexture( pDevice );

流程都是一样的，计算所需要的变量，然后设置变量，渲染到RenderTarget。

接下来的DownSampling就不说了。然后就到了Blur，这个例子中先进行水平模糊，再进行垂直模糊。计算模糊值中用到了高斯分布函数。

那么下一节将进行最后效果合成代码的阅读。