DX11_基于GPU_ComputeShader的3D精确拾取

这里使用ComputeShader做拾取，主要为了熟悉下ComputeShader，为自己后面一个项目做准备。拾取基本原理前面博客也讲了，都差不多，将射线从屏幕坐标系转换到物体局部坐标系，然后再判断三角形是否被射线射中。主要是代码的实施上不一样，这里我尝试并行地通过ComputeShader，由线程i来负责判断三角形i是否被选中。

HLSL的代码：

//=========================================

//compute shader base technology

//======================================

#define BLOCK_SIZE 32

struct VertexStruc

{

float3 posW;

float3 normalW;

float2 texcoord;

};

struct PickedStruc

{

int picked;//记录三角形i是否被选中，选中为1，否则为0

};

StructuredBuffer<int> indiceBuf;

StructuredBuffer<VertexStruc> inTriPointBuf;

RWStructuredBuffer<PickedStruc> pickedTriBoolArray;

//每个线程负责一个三角形

[numthreads(BLOCK_SIZE, 1, 1)]

void CS_PickTriangle( uint3 Gid : SV_GroupID, uint3 DTid : SV_DispatchThreadID, uint3 GTid : SV_GroupThreadID, uint GI : SV_GroupIndex )

{

if(DTid.x>=numFaces)return ;

根据之前博客，把射线从屏幕坐标转换到物体的局部坐标

float3 pickOrigin=float3(0.0f,0.0f,0.0f);

float3 pickDirection;

pickDirection.x=(2.0f*winPos.x/backBufferDesc.x-1.0f)/projMtx[0][0];

pickDirection.y=(-2.0f*winPos.y/backBufferDesc.y+1.0f)/projMtx[1][1];

pickDirection.z=1.0f;

pickOrigin=mul(float4(pickOrigin,1.0f),invViewMtx).xyz;

pickDirection=mul(float4(pickDirection,0.0f),invViewMtx).xyz;

pickOrigin=mul(float4(pickOrigin,1.0f),invWorldMtx).xyz;

pickDirection=mul(float4(pickDirection,0.0f),invWorldMtx).xyz;

float u=0;

float v=0;

float t=0;

float3 pos[3];

    //读取第DTid.x个三角形的三个顶点位置。

for(int i=0;i<3;i++)

{

pos[i]=inTriPointBuf[ indiceBuf[DTid.x*3+i]].posW;

}

    //由第DTid.x个线程判定第DTid.x三角形是否被射线选中

if(IntersectTriangle(pickOrigin,pickDirection,pos[0],pos[1],pos[2],t,u,v))

{

   pickedTriBoolArray[DTid.x].picked=1;

}

else

{

   pickedTriBoolArray[DTid.x].picked=0;

}

return ;

}

比较麻烦的是Directx中的代码。因为ComputeShader只理解StructuredBuffer，不理解VertexBuffer和IndexBuffer，所以要把VertexBuffer和IndexBuffer中的数据拷贝到相应的StructuredBuffer中。

HRESULT Mesh::DrawPickMesh_CSAPBUF(CModelViewerCamera *pCamera,POINT cursor,POINT backDesc)

{

HRESULT hr=S_OK;

    //调用拾取算法

GetPickedTriangleArray_CS(pCamera,cursor,backDesc);

//绘制选中的三角形

DrawPickedTriangleArray_CS(pCamera);

    //以网格形式绘制其他三角形，便于显示

DrawFrameMesh(pCamera);

return hr;

}

HRESULT Mesh::GetPickedTriangleArray_CS(CModelViewerCamera *pCamera,POINT cursor,POINT backDesc)

{

HRESULT hr=S_OK;

D3D11_BUFFER_DESC bufDesc1;

D3D11_BUFFER_DESC bufDesc2;

ZeroMemory(&bufDesc1,sizeof(D3D11_BUFFER_DESC));

ZeroMemory(&bufDesc2,sizeof(D3D11_BUFFER_DESC));

//把VertexBuffer中的数据拷贝到相应的StructuredBuffer中并创建相应ResourceView。

m_pVsStrucBuffer=NULL;

ID3D11Buffer *pSrcBuffer=NULL;

pSrcBuffer=m_pMesh11->GetVB11(0,0);

pSrcBuffer->GetDesc(&bufDesc2);

bufDesc1.ByteWidth=bufDesc2.ByteWidth;

bufDesc1.BindFlags=D3D11_BIND_SHADER_RESOURCE;

bufDesc1.CPUAccessFlags=0;

bufDesc1.MiscFlags=D3D11_RESOURCE_MISC_BUFFER_STRUCTURED;

bufDesc1.StructureByteStride=sizeof(MeshVertex);

bufDesc1.Usage=D3D11_USAGE_DEFAULT;

V_RETURN(m_pDevice->CreateBuffer(&bufDesc1,NULL,&m_pVsStrucBuffer));

m_pContext->CopyResource(m_pVsStrucBuffer,pSrcBuffer);

#if defined (DEBUG)||defined(_DEBUG)

m_pVsStrucBuffer->SetPrivateData(WKPDID_D3DDebugObjectName ,sizeof("m_pVsStrucBuffer")-1,"m_pVsStrucBuffer");

#endif

// 创建相应ResourceView。

ID3D11ShaderResourceView *pVSStrucBufSRV;

D3D11_SHADER_RESOURCE_VIEW_DESC srvDesc;

ZeroMemory(&srvDesc,sizeof(D3D11_SHADER_RESOURCE_VIEW_DESC));

srvDesc.Buffer.FirstElement=0;

srvDesc.Buffer.NumElements=m_pMesh11->GetNumVertices(0,0);

srvDesc.Format=DXGI_FORMAT_UNKNOWN;

srvDesc.ViewDimension=D3D11_SRV_DIMENSION_BUFFER;

V_RETURN(m_pDevice->CreateShaderResourceView(m_pVsStrucBuffer,&srvDesc,&pVSStrucBufSRV));

#if defined (DEBUG)||defined(_DEBUG)

pVSStrucBufSRV->SetPrivateData(WKPDID_D3DDebugObjectName ,sizeof("pVSStrucBufSRV")-1,"pVSStrucBufSRV");

#endif

//把IndexBuffer中的数据拷贝到相应的StructuredBuffer中并创建相应ResourceView。

m_pIndexStrucBuffer=NULL;

pSrcBuffer=m_pMesh11->GetIB11(0);

pSrcBuffer->GetDesc(&bufDesc2);

bufDesc1.ByteWidth=bufDesc2.ByteWidth;

bufDesc1.BindFlags=D3D11_BIND_SHADER_RESOURCE;

bufDesc1.CPUAccessFlags=0;

bufDesc1.MiscFlags=D3D11_RESOURCE_MISC_BUFFER_STRUCTURED;

if(m_pMesh11->GetIBFormat11(0)==DXGI_FORMAT_R16_UINT)

bufDesc1.StructureByteStride=2;

else

bufDesc1.StructureByteStride=4;

bufDesc1.Usage=D3D11_USAGE_DEFAULT;

V_RETURN(m_pDevice->CreateBuffer(&bufDesc1,NULL,&m_pIndexStrucBuffer));

m_pContext->CopyResource(m_pIndexStrucBuffer,pSrcBuffer);

#if defined (DEBUG)||defined(_DEBUG)

m_pIndexStrucBuffer->SetPrivateData(WKPDID_D3DDebugObjectName ,sizeof("m_pIndexStrucBuffer")-1,"m_pIndexStrucBuffer");

#endif

//创建相应ResourceView。

ID3D11ShaderResourceView *pIndexStrucBufSRV;

ZeroMemory(&srvDesc,sizeof(D3D11_SHADER_RESOURCE_VIEW_DESC));

srvDesc.Buffer.FirstElement=0;

srvDesc.Buffer.NumElements=m_pMesh11->GetNumIndices(0);

srvDesc.Format=DXGI_FORMAT_UNKNOWN;

srvDesc.ViewDimension=D3D11_SRV_DIMENSION_BUFFER;

V_RETURN(m_pDevice->CreateShaderResourceView(m_pIndexStrucBuffer,&srvDesc,&pIndexStrucBufSRV));

#if defined (DEBUG)||defined(_DEBUG)

pIndexStrucBufSRV->SetPrivateData(WKPDID_D3DDebugObjectName ,sizeof("pIndexStrucBufSRV")-1,"pIndexStrucBufSRV");

#endif

//创建一个Buffer来存储三角形i是否被选中。

m_pPickedTriBoolArrBuf=NULL;

ZeroMemory(&bufDesc1,sizeof(D3D11_BUFFER_DESC));

bufDesc1.ByteWidth=m_pMesh11->GetNumIndices(0)/3*sizeof(PickedStruc);

bufDesc1.BindFlags=D3D11_BIND_UNORDERED_ACCESS;

bufDesc1.CPUAccessFlags=0;

bufDesc1.MiscFlags=D3D11_RESOURCE_MISC_BUFFER_STRUCTURED;

bufDesc1.StructureByteStride=sizeof(PickedStruc);

bufDesc1.Usage=D3D11_USAGE_DEFAULT;

V_RETURN(m_pDevice->CreateBuffer(&bufDesc1,NULL,&m_pPickedTriBoolArrBuf));

#if defined (DEBUG)||defined(_DEBUG)

m_pPickedTriBoolArrBuf->SetPrivateData(WKPDID_D3DDebugObjectName ,sizeof("m_pPickedTriBoolArrBuf")-1,"m_pPickedTriBoolArrBuf");

#endif

//创建相应ResourceView。

m_pPickedTriBoolArrUAV=NULL;

D3D11_UNORDERED_ACCESS_VIEW_DESC uavDesc;

ZeroMemory(&uavDesc,sizeof(D3D11_UNORDERED_ACCESS_VIEW_DESC));

uavDesc.Buffer.FirstElement=0;

uavDesc.Buffer.Flags=0;

uavDesc.Buffer.NumElements=m_pMesh11->GetNumIndices(0)/3;

uavDesc.Format=DXGI_FORMAT_UNKNOWN;

uavDesc.ViewDimension=D3D11_UAV_DIMENSION_BUFFER;

V_RETURN(m_pDevice->CreateUnorderedAccessView(m_pPickedTriBoolArrBuf,&uavDesc,&m_pPickedTriBoolArrUAV));

#if defined (DEBUG)||defined(_DEBUG)

m_pPickedTriBoolArrUAV->SetPrivateData(WKPDID_D3DDebugObjectName ,sizeof("m_pPickedTriBoolArrUAV")-1,"m_pPickedTriBoolArrUAV");

#endif

//calculate the matrix

D3DXMATRIX invWorld;

D3DXMatrixInverse(&invWorld,0,&m_World);

D3DXMATRIX viewMtx=*pCamera->GetViewMatrix();

D3DXMATRIX invViewMtx;

D3DXMatrixInverse(&invViewMtx,0,&viewMtx);

const D3DXMATRIX projMtx=*pCamera->GetProjMatrix();

//calculate the cursor and backbuffer

MFloat2 mcur;

MFloat2 mback;

mcur.x=(float)cursor.x;

mcur.y=(float)cursor.y;

mback.x=(float)backDesc.x;

mback.y=(float)backDesc.y;

//set the effect variable

m_pfxInterViewMtx->SetMatrix((float*)&viewMtx);

m_pfxInterInvViewMtx->SetMatrix((float*)&invViewMtx);

m_pfxInterProjMtx->SetMatrix((float*)&projMtx);

m_pfxInterWorldMtx->SetMatrix((float*)(&m_World));

m_pfxInterInvWorldMtx->SetMatrix((float*)&invWorld);

m_pfxInterWinPos->SetRawValue((void*)&mcur,0,sizeof(MFloat2));

m_pfxInterBackbufferDesc->SetRawValue((void*)&mback,0,sizeof(MFloat2));

m_pfxIndexStrucSRV->SetResource(pIndexStrucBufSRV);

m_pfxVertexStrucSRV->SetResource(pVSStrucBufSRV);

//m_pfxVSSrucAppUAV->SetUnorderedAccessView(m_pPickedTriBoolArrUAV);

UINT numfaces=m_pMesh11->GetNumIndices(0)/3;

m_pfxNumFaces->SetInt(numfaces);

m_pfxPickedTriBoolArr->SetUnorderedAccessView(m_pPickedTriBoolArrUAV);

//m_pfxTestBufUAV->SetUnorderedAccessView(pTestBufUAV);

D3DX11_TECHNIQUE_DESC techDesc;

//1apply intersected technique

m_pfxCSInterTech->GetDesc(&techDesc);

for(int i=0;i<techDesc.Passes;i++)

{

m_pfxCSInterTech->GetPassByIndex(i)->Apply(0,m_pContext);

UINT groupSizeX=(numfaces+CS_APP_BLOCK_SIZE-1)/CS_APP_BLOCK_SIZE;

m_pContext->Dispatch(groupSizeX,1,1);

}

SAFE_RELEASE(pIndexStrucBufSRV);

SAFE_RELEASE(pVSStrucBufSRV);

return hr;

}

//绘制那些被选中的三角形

HRESULT Mesh::DrawPickedTriangleArray_CS(CModelViewerCamera *pCamera)

{

HRESULT hr=S_OK;

//m_pPickedTriBoolArrBuf，看哪个三角形被选中

ID3D11Buffer* pReadPickedBuf=NULL;

pReadPickedBuf=CopyToDebugBuffer(m_pPickedTriBoolArrBuf);

D3D11_MAPPED_SUBRESOURCE mapSubData;

ZeroMemory(&mapSubData,sizeof(D3D11_MAPPED_SUBRESOURCE));

m_pContext->Map(pReadPickedBuf,0,D3D11_MAP_READ,0,&mapSubData);

PickedStruc *pBoolArr=(PickedStruc*)mapSubData.pData;

m_pContext->Unmap(pReadPickedBuf,0);

//读出模型所有的VertexBuffer

ID3D11Buffer* pReadVertexBuffer=NULL;

pReadVertexBuffer=CopyToDebugBuffer(m_pVsStrucBuffer);

ZeroMemory(&mapSubData,sizeof(D3D11_MAPPED_SUBRESOURCE));

m_pContext->Map(pReadVertexBuffer,0,D3D11_MAP_READ,0,&mapSubData);

MeshVertex *pVertex=(MeshVertex*)mapSubData.pData;

m_pContext->Unmap(pReadVertexBuffer,0);

//读出模型所有的IndexBuffer

ID3D11Buffer* pReadIndexBuffer=NULL;

pReadIndexBuffer=CopyToDebugBuffer(m_pIndexStrucBuffer);

ZeroMemory(&mapSubData,sizeof(D3D11_MAPPED_SUBRESOURCE));

m_pContext->Map(pReadIndexBuffer,0,D3D11_MAP_READ,0,&mapSubData);

UINT *pIndex=(UINT*)mapSubData.pData;

m_pContext->Unmap(pReadIndexBuffer,0);

//看哪些三角形被选中if(picked==1)

UINT numfaces=m_pMesh11->GetNumIndices(0)/3;

MeshVertex *pPickedVertex=new MeshVertex[300];

int pickedNum=0;

for(int i=0;i<numfaces;i++)

{

if(pBoolArr[i].picked==1)

{

//这个三角形被选中了，读出它的三个点来绘制

for(int j=0;j<3;j++)

{

pPickedVertex[3*pickedNum+j].normal=pVertex[pIndex[3*i+j]].normal;

pPickedVertex[3*pickedNum+j].pos=pVertex[pIndex[3*i+j]].pos;

pPickedVertex[3*pickedNum+j].texcoord=pVertex[pIndex[3*i+j]].texcoord;

}

pickedNum++;

}

}

//根据上面读出的顶点绘制三角形

//根据上面读出的点生成一个用来绘制的Vertex Buffer

if(pickedNum>0)

{

ID3D11Buffer *pPickedVertexBuffer=NULL;

D3D11_BUFFER_DESC bufDesc;

ZeroMemory(&bufDesc,sizeof(D3D11_BUFFER_DESC));

bufDesc.ByteWidth=pickedNum*3*sizeof(MeshVertex);

bufDesc.BindFlags=D3D11_BIND_VERTEX_BUFFER;

bufDesc.CPUAccessFlags=0;

bufDesc.MiscFlags=0;

bufDesc.StructureByteStride=0;

bufDesc.Usage=D3D11_USAGE_DEFAULT;

D3D11_SUBRESOURCE_DATA vSSubData;

ZeroMemory(&vSSubData,sizeof(D3D11_SUBRESOURCE_DATA));

vSSubData.pSysMem=(void*)pPickedVertex;

m_pDevice->CreateBuffer(&bufDesc,&vSSubData,&pPickedVertexBuffer);

//绘制上面刚创建的三角形的vertex buffer

D3DX11_TECHNIQUE_DESC techDesc;

ZeroMemory(&techDesc,sizeof(D3DX11_TECHNIQUE_DESC));

m_pfxWorldMtx->SetMatrix((float*)&m_World);

m_pfxViewMtx->SetMatrix((float*)pCamera->GetViewMatrix());

m_pfxProjMtx->SetMatrix((float*)pCamera->GetProjMatrix());

m_pfxMeshTech->GetDesc(&techDesc);

m_pContext->IASetInputLayout(m_pInputLayout);

m_pContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST);

UINT stride=sizeof(MeshVertex);

UINT offset=0;

m_pContext->IASetVertexBuffers(0,1,&pPickedVertexBuffer,&stride,&offset);

for(int i=0;i<techDesc.Passes;i++)

{

m_pfxMeshTech->GetPassByIndex(0)->Apply(0,m_pContext);

m_pContext->Draw(3*pickedNum,0);

}

SAFE_RELEASE(pPickedVertexBuffer);

}

SAFE_RELEASE(pReadPickedBuf);

SAFE_RELEASE(pReadVertexBuffer);

SAFE_RELEASE(pReadIndexBuffer);

delete[] pPickedVertex;

return hr;

}

最后以网格形式绘制其余的三角形

void Mesh::DrawFrameMesh(CModelViewerCamera* pCamera)

{

m_pfxWorldMtx->SetMatrix((float*)&m_World);

m_pfxViewMtx->SetMatrix((float*)pCamera->GetViewMatrix());

m_pfxProjMtx->SetMatrix((float*)pCamera->GetProjMatrix());

D3DX11_TECHNIQUE_DESC techDesc;

ZeroMemory(&techDesc,sizeof(D3DX11_TECHNIQUE_DESC));

UINT stride=m_pMesh11->GetVertexStride(0,0);

UINT offset=0;

ID3D11Buffer *pVertexBuffer[1];

pVertexBuffer[0]=m_pMesh11->GetVB11(0,0);

m_pContext->IASetVertexBuffers(0,1,pVertexBuffer,&stride,&offset);

m_pContext->IASetIndexBuffer(m_pMesh11->GetIB11(0),m_pMesh11->GetIBFormat11(0),0);

m_pContext->IASetInputLayout(m_pInputLayout);

m_pfxWireFrameTech->GetDesc(&techDesc);

SDKMESH_SUBSET *pSubSet=NULL;

for(int i=0;i<techDesc.Passes;i++)

{

for(int subset=0;subset<m_pMesh11->GetNumSubsets(0);subset++)

{

pSubSet=m_pMesh11->GetSubset(0,subset);

m_pfxWireFrameTech->GetPassByIndex(0)->Apply(0,m_pContext);

//get primitiveType

D3D11_PRIMITIVE_TOPOLOGY primType;

primType=CDXUTSDKMesh::GetPrimitiveType11((SDKMESH_PRIMITIVE_TYPE)pSubSet->PrimitiveType );

m_pContext->IASetPrimitiveTopology(primType);

//get material

ID3D11ShaderResourceView *pSV=NULL;

pSV=m_pMesh11->GetMaterial(pSubSet->MaterialID)->pDiffuseRV11;

m_pfxDiffTex->SetResource(pSV);

//draw the wireframe mesh

   m_pContext->DrawIndexed((UINT)pSubSet->IndexCount,0,(UINT)pSubSet->VertexStart);

}

}

}

最后拾取效果

DX11_基于GPU_ComputeShader的3D精确拾取
因为完整的代码太琐碎又太大了，我就不一一贴上了。完整的代码可以从这里下载：http://download.csdn.net/detail/qiul12345/3952333。

DX11_基于GPU_ComputeShader的3D精确拾取

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