[vtkusers] How does vtkGeometryFilter handle 2D cells overlaid on a 3D cell?
Matt Sutton
matt.sutton at padtinc.com
Wed Sep 12 09:58:23 EDT 2012
Hello,
I'm replying to my own post which I hope is kosher with the list, but I determined from my test case that indeed vtkGeometryFilter seems to show preference to 2D cells overlaid on "external" faces of 3D cells during the extraction process. For what it is worth, here is my test function.
int geometry_extraction_test(int argc, char *argv[])
{
VTK_CREATE(vtkUnstructuredGrid, pMesh);
VTK_CREATE(vtkPoints, pPoints);
VTK_CREATE(vtkIdTypeArray, pNodeIds);
VTK_CREATE(vtkIdTypeArray, pElementIds);
VTK_CREATE(vtkIdTypeArray, pElemPedigreeIds);
VTK_CREATE(vtkIdTypeArray, pNodePedigreeIds);
// Use an offset node number so we can test passing
// those through the filters.
vtkIdType node_num = 1;
std::vector<vtkIdType> node_ids;
node_ids.push_back(pPoints->InsertNextPoint(0,0,0));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(1,0,0));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(1,1,0));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(0,1,0));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(0,0,1));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(1,0,1));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(1,1,1));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(0,1,1));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(0,0,2));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(1,0,2));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(1,1,2));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
node_ids.push_back(pPoints->InsertNextPoint(0,1,2));
pNodeIds->InsertNextValue(node_num++);
pNodePedigreeIds->InsertNextValue(0);
pElemPedigreeIds->InsertNextValue(0);
pElemPedigreeIds->InsertNextValue(0);
pElemPedigreeIds->InsertNextValue(2);
pElemPedigreeIds->InsertNextValue(2);
// Create 2 hexas
vtkIdType vtkHexaIds[8];
for(int i = 0; i < 8; i++) {
vtkHexaIds[i] = node_ids[i];
}
pMesh->InsertNextCell(VTK_HEXAHEDRON, 8, vtkHexaIds);
pElementIds->InsertNextValue(3);
for(int i = 0; i < 8; i++) {
vtkHexaIds[i] = node_ids[i+4];
}
pMesh->InsertNextCell(VTK_HEXAHEDRON, 8, vtkHexaIds);
pElementIds->InsertNextValue(4);
// Create 2 quads
vtkIdType vtkQuadIds[4];
vtkQuadIds[0] = node_ids[1];
vtkQuadIds[1] = node_ids[0];
vtkQuadIds[2] = node_ids[3];
vtkQuadIds[3] = node_ids[2];
pMesh->InsertNextCell(VTK_QUAD, 4, vtkQuadIds);
pElementIds->InsertNextValue(32);
for(int i = 0; i < 4; i++) {
vtkQuadIds[i] = node_ids[i+8];
}
pMesh->InsertNextCell(VTK_QUAD, 4, vtkQuadIds);
pElementIds->InsertNextValue(33);
pMesh->SetPoints(pPoints);
pMesh->GetPointData()->SetGlobalIds(pNodeIds);
pMesh->GetPointData()->SetPedigreeIds(pNodePedigreeIds);
pMesh->GetCellData()->SetGlobalIds(pElementIds);
pMesh->GetCellData()->SetPedigreeIds(pElemPedigreeIds);
pMesh->Squeeze();
pMesh->GetPointData()->CopyGlobalIdsOn();
pMesh->GetPointData()->CopyPedigreeIdsOn();
pMesh->GetCellData()->CopyGlobalIdsOn();
pMesh->GetCellData()->CopyPedigreeIdsOn();
// Now, extract the geometry
VTK_CREATE(vtkGeometryFilter, pGeomFilter);
pGeomFilter->SetInput(pMesh);
pGeomFilter->Update();
vtkPolyData *pPolys = pGeomFilter->GetOutput();
pPolys->GetPolys()->InitTraversal();
vtkIdType npts = 0;
vtkIdType *pnts = nullptr;
int cell_count = 0;
vtkIdTypeArray *pGlobalIds = nullptr;
pGlobalIds = vtkIdTypeArray::SafeDownCast(pPolys->GetPointData()->GetGlobalIds());
while(pPolys->GetPolys()->GetNextCell(npts, pnts) != 0) {
cell_count++;
std::cout << "Number of points in cell: " << npts << endl;
std::cout << "\tMesh ids: ";
for(int i = 0; i < npts; i++) {
std::cout << pnts[i] << " ";
}
std::cout << std::endl;
std::cout << "\tGlobal ids: ";
for(int i = 0; i < npts; i++) {
std::cout << pGlobalIds->GetValue(pnts[i]) << " ";
}
std::cout << std::endl;
}
std::cout << "Total Number of cells: " << cell_count << std::endl;
vtkIdTypeArray *pPedigreeIds = nullptr;
vtkIdTypeArray *pCellGlobalIds = nullptr;
pPedigreeIds = vtkIdTypeArray::SafeDownCast(pPolys->GetCellData()->GetPedigreeIds());
pCellGlobalIds = vtkIdTypeArray::SafeDownCast(pPolys->GetCellData()->GetGlobalIds());
for(vtkIdType i = 0; i < pPolys->GetNumberOfCells(); i++) {
std::cout << "Cell " << i << " PedigreeID: " << pPedigreeIds->GetValue(i) << std::endl;
std::cout << "Cell " << i << " GlobalID: " << pCellGlobalIds->GetValue(i) << std::endl;
}
std::cout << std::endl << std::endl;
std::cout << "Selection Logic" << std::endl << std::endl;
//////////////////////////////////////////////////////////////////////
// Test the selection logic in VTK
VTK_CREATE(vtkSelection, pSelection);
VTK_CREATE(vtkSelectionNode, pNode);
VTK_CREATE(vtkExtractSelection, pExtractor);
pNode->SetContentType(vtkSelectionNode::GLOBALIDS);
pNode->SetFieldType(vtkSelectionNode::POINT);
VTK_CREATE(vtkIdTypeArray, pSelArray);
pSelArray->InsertNextValue(1);
pSelArray->InsertNextValue(2);
pSelArray->InsertNextValue(5);
pSelArray->InsertNextValue(6);
pSelArray->InsertNextValue(9);
pSelArray->InsertNextValue(10);
pNode->SetSelectionList(pSelArray);
pNode->GetProperties()->Set(vtkSelectionNode::CONTAINING_CELLS(), 1);
pNode->GetProperties()->Set(vtkSelectionNode::INVERSE(), 1);
pSelection->AddNode(pNode);
pExtractor->SetInput(0, pPolys);
pExtractor->SetInput(1, pSelection);
pExtractor->Update();
vtkUnstructuredGrid *pGrid = vtkUnstructuredGrid::SafeDownCast(pExtractor->GetOutput());
cell_count = 0;
vtkIdTypeArray *pSelMeshGIDs = vtkIdTypeArray::SafeDownCast(pGrid->GetPointData()->GetGlobalIds());
if(pGrid != nullptr) {
for(int i = 0; i < pGrid->GetNumberOfCells(); i++) {
std::cout << "Cell: " << i << " Points GIDs: ";
for(int j = 0; j < pGrid->GetCell(i)->GetNumberOfPoints(); j++) {
std::cout << pSelMeshGIDs->GetValue(pGrid->GetCell(i)->GetPointId(j)) << " ";
}
std::cout << std::endl;
}
std::cout << "Total Number of cells: " << pGrid->GetNumberOfCells() << std::endl;
}
return 0;
}
-----Original Message-----
From: Matt Sutton [mailto:matt.sutton at padtinc.com]
Sent: Tuesday, September 11, 2012 8:17 AM
To: vtkusers at vtk.org
Subject: [vtkusers] How does vtkGeometryFilter handle 2D cells overlaid on a 3D cell?
Hello,
I realize I can create a test case to determine the behavior, but I thought I would ask the list first. How does the vtkGeometryFilter handle the case where you have a vtkUnstructuredGrid consisting of 3D cells (Hexas or Tets) that have 2D cells (Quads or tris) paved on their outer surface already? Will it extract a single 2D cell for this face comprising the existing overlaid 2D cell, or will it extract two 2D cells; one for the existing and one for the 3D face? If it does the latter, is there a clean way to get at only one of these faces? For my case, I don't think it would matter which one, but perhaps I would preferentially choose to keep the existing 2D cell. Maybe this is where pedigreeIDs are helpful? I have to admit, I'm still trying to get my head around those.
Thanks,
Matt
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Matthew Sutton
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matt.sutton at padtinc.com
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