在Havok Vision 中创建后期处理效果

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如果有人参考了 官方手册的教程 Tutorial: Creating Custom Post-Processing Effects
然后使用 PA 的 vGameSolutionCreator 默认设置创建项目，会发现运行报错
active renderer does not provide all buffers required by the post processor.Execute

经过debug,发现默认创建的render node 实际上是 VMobileForwardRenderingSystem
它只支持一个bufferflag 就是 VBUFFERFLAG_FINALCOLOR

让我们从头开始
postprocessing
打开 VForge 编写我们的后期处理特效，这次范例就用径向模糊(Dx9,Dx11)

打开Shader Code Editor
顶点Code

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#include <Shaders/VisionCommon.inc>

#ifdef _VISION_DX11
cbuffer g_GlobalConstantBufferObject : register (b1)
{
  float4x4 matMVP : packoffset(c4);   // model view projection matrix
}
#else
  float4x4 matMVP : register(c8);
#endif
 
struct Data_In
{
    float4 VectPos  : POSITION;
    float4 UV       : TEXCOORD0;
};

struct Data_Out
{
    float4 ProjPos  : SV_POSITION;
    float4 UV       : TEXCOORD0;
};

Data_Out vs_main( Data_In In )
{
    Data_Out output;
    output.ProjPos = mul(matMVP, In.VectPos);
    output.UV = In.UV;
    return output;
}

像素 Code

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#include <Shaders/VisionCommon.inc>

#if defined(_VISION_DX11)
Texture2D <float4> BaseTexture        : register(t0);
sampler            BaseTextureSampler : register(s0);

cbuffer g_GlobalConstantBufferObject : register (b2)
{
    float SampleDist                      : register(c0);
    float SampleStrength                  : register(c1);
}

#else
sampler2D          BaseTexture        : register(s0);
float SampleDist;
float SampleStrength;
#endif

struct Data_In
{
    float4 ProjPos  : SV_POSITION;
    float4 UV       : TEXCOORD0;
};

float4 ps_main( Data_In In ) : SV_Target
{
    float2 dir = 0.5 - In.UV;
    float dist = length(dir);
    dir /= dist;
    float4 color = vTex2D(BaseTexture, BaseTextureSampler, In.UV);
    float4 sum = color;
   
    float startValue = -0.08;
    for(int i = 0; i < 10; i++)
    {
        sum += vTex2D(BaseTexture,BaseTextureSampler,In.UV + dir * startValue * SampleDist);
        startValue += 0.3;
    }
   
    sum /= 11.0;
   
    float t = saturate(dist * SampleStrength);
   
    float4 final = lerp(color, sum, t);
   
    return final;
}

Shader Tech的名字为 RadialBlurShader 然后保存 ShaderLib
之后编写我们的 Vision Code

头文件
CustomPostProcessor.h

class CustomPostProcessor : public VPostProcessingBaseComponent
{
public:
	CustomPostProcessor(float fSampleDist = 0.5f, float fSampleStrength = 10.0f);
	virtual ~CustomPostProcessor();

	virtual void Serialize( VArchive &ar ) HKV_OVERRIDE;
	virtual void OnHandleCallback(IVisCallbackDataObject_cl *pData);

	float m_fSampleDist;
	float m_fSampleStrength;
private:
	V_DECLARE_SERIAL_DLLEXP(CustomPostProcessor,SAMPLEPLUGIN_IMPEXP);
	V_DECLARE_VARTABLE(CustomPostProcessor, SAMPLEPLUGIN_IMPEXP);
        virtual void Execute() HKV_OVERRIDE;
	void SetupContext();
	void RemoveContext();

	void CreateShaders();
	void RemoveShaders();

	//shader
	VCompiledTechniquePtr m_spCustomTechnique;
};

cpp文件

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V_IMPLEMENT_SERIAL( CustomPostProcessor, VPostProcessingBaseComponent, 0, &g_myComponentModule );

START_VAR_TABLE(CustomPostProcessor, VPostProcessingBaseComponent, "VCustomPostProcessor", 0, "")
    DEFINE_VAR_FLOAT(CustomPostProcessor, m_fSampleDist, "m_fSampleDist", "0.0", 0, "Slider(0,100)");
    DEFINE_VAR_FLOAT(CustomPostProcessor, m_fSampleStrength, "m_fSampleStrength", "0.0", 0, "Slider(0,100)");
END_VAR_TABLE

CustomPostProcessor::CustomPostProcessor( float fSampleDist /*= 0.5f*/, float fSampleStrength/* = 10.0f*/ )
:m_spCustomTechnique(NULL)
{
    m_fSampleDist = fSampleDist;
    m_fSampleStrength = fSampleStrength;

    m_iRequiredBufferFlags = VBUFFERFLAG_FINALCOLOR;

    m_fPriority = VIS_RENDERCONTEXTPRIORITY_POSTPROCESSOR_RESOLVED + 6000.0f;

    // Our post-processor covers the entire render target
    m_bufferUsageFlags = DRAWS_FULLSCREEN_QUAD;

    Vision::Callbacks.OnUpdateSceneBegin += this;
}

CustomPostProcessor::~CustomPostProcessor()
{
    Vision::Callbacks.OnUpdateSceneBegin -= this;
}

void CustomPostProcessor::Serialize( VArchive &ar )
{
    char iLocalVersion = 0;
    if(ar.IsLoading())
    {
        ar >> iLocalVersion;
        ar >> m_bActive;
        ar >> m_fSampleDist;
        ar >> m_fSampleStrength;
    }else{
        ar << iLocalVersion;
        ar << m_bActive;
        ar << m_fSampleDist;
        ar << m_fSampleStrength;
    }
}

void CustomPostProcessor::InitializePostProcessor()
{
    if(m_bIsInitialized)
    {
        return;
    }

    SetupContext();
    CreateShaders();

    m_bIsInitialized = true;
}

void CustomPostProcessor::DeInitializePostProcessor()
{
    if(!m_bIsInitialized)
    {
        return;
    }

    RemoveShaders();
    RemoveContext();

    m_bIsInitialized = false;
}

void CustomPostProcessor::Execute()
{

    VCompiledShaderPass * pPass = m_spCustomTechnique->GetShader(0);

    IVRender2DInterface *pRender = Vision::RenderLoopHelper.BeginOverlayRendering();
    Overlay2DVertex_t * pVertex = GetOwner()->GetRendererNodeHelper()->GetOverlayVertices();
    pRender->Draw2DBufferWithShader(6, pVertex, m_spSourceTextures[0], *pPass);
    Vision::RenderLoopHelper.EndOverlayRendering();
}

void CustomPostProcessor::SetupContext()
{
    VisRenderContext_cl * pTargetContext = GetTargetContext();

    pTargetContext->SetName("VCustomPostProcessor - Target Context");

    //在渲染节点中注册上下文
    GetOwner()->AddContext(pTargetContext);

    //获取纹理引用
    m_spSourceTextures[0] = GetOwner()->GetGBuffer(IVRendererNode::VGBT_Diffuse);
    m_iNumSourceTextures = 1;
}

void CustomPostProcessor::RemoveContext()
{
    m_spSourceTextures[0] = NULL;

    GetOwner()->RemoveContext(GetTargetContext());
}

void CustomPostProcessor::CreateShaders()
{
    if(Vision::Shaders.LoadShaderLibrary("\shaders\EasyGameShader.ShaderLib"))
    {
        m_spCustomTechnique = Vision::Shaders.CreateTechnique("RadialBlurShader", NULL, NULL, EFFECTCREATEFLAG_FORCEUNIQUE);
        if(m_spCustomTechnique){
            //后期渲染不需要深度
            m_spCustomTechnique->GetShader(0)->GetRenderState()->GetDepthStencilState().m_bDepthTestEnabled = false;
            m_spCustomTechnique->GetShader(0)->GetRenderState()->GetDepthStencilState().ComputeHash();
        }
    }
}

void CustomPostProcessor::RemoveShaders()
{
    m_spCustomTechnique = NULL;
}

void CustomPostProcessor::OnHandleCallback( IVisCallbackDataObject_cl *pData )
{
    if(pData->m_pSender== &Vision::Callbacks.OnUpdateSceneBegin)
    {
        if(m_spCustomTechnique){
            VCompiledShaderPass * pPass = m_spCustomTechnique->GetShader(0);
            const float * fSampleDist = &m_fSampleDist;
            const float * fSampeStrength = &m_fSampleStrength;
            pPass->GetConstantBuffer(VSS_PixelShader)->SetSingleParameterF("SampleDist", fSampleDist);
            pPass->GetConstantBuffer(VSS_PixelShader)->SetSingleParameterF("SampleStrength", fSampeStrength);
            pPass->m_bModified = true;
        }
    }
}

最后加载这个后期处理特效
在 GameManager 的 OnAfterSceneLoaded callback 中

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CustomPostProcessor * tmp = new CustomPostProcessor(0.5f,10.0f);
Vision::Renderer.GetRendererNode(0)->AddComponent(tmp);
tmp->SetActive(true);

大功告成，运行看看吧

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