Hi all,
I am trying to use vtk to load in an object stored in an .stl file, and fill a structured 3D grid with the volume of the object present in each grid cell.
(If there is an obvious way to do this which I am missing, which doesn’t use ImageData and polyData, that would also be great!)
I can load in the .stl files into a vtkPolyData, and that works fine. Then, given a vtkImageData filled with either volume or signed-distance, I can access the imageData fine. But it is going from vtkPolyData to vtkImageData that doesn’t work.
I tried using vtkSurfaceReconstructionFilter, then vtkImageResize and getting the data from there. This does work for simple shapes, but when I try a complex mesh like Orion Capsule | 3D Resources , the surface it produces looks awful - some parts of the domain is just filled with random mess. I feel like given that I already have a definition of the surface connectivity, doing a surface reconstruction from a point cloud is just not using that information? The reconstruction seems to fall down in areas that don’t have very many points, which makes sense.
Is there a better way to do this?
If anyone has any insight on the best way to do this I would be immensely grateful! (My current code is below)
Many thanks!
vtkSmartPointer<vtkPolyData> ReadPolyData(std::string const& fileName)
{
vtkSmartPointer<vtkPolyData> polyData;
std::string extension = "";
if (fileName.find_last_of(".") != std::string::npos)
{
extension = fileName.substr(fileName.find_last_of("."));
}
// Make the extension lowercase
std::transform(extension.begin(), extension.end(), extension.begin(),
::tolower);
if (extension == ".ply")
{
auto reader = vtkSmartPointer<vtkPLYReader>::New();
reader->SetFileName(fileName.c_str());
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".stl")
{
auto reader = vtkSmartPointer<vtkSTLReader>::New();
reader->SetFileName(fileName.c_str());
reader->Update();
polyData = reader->GetOutput();
}
return polyData;
}
STLReader(std::string inputFilename, const Real* dx, const Real* prob_lo, const Real* prob_hi)
{
//dx stores cell size
//prob_lo and and prob_hi store the coordinates of my 3D domain
double bounds[6];
for(int d=0 ; d<3 ; d++)
{
bounds[2*d] = prob_lo[d] + dx[d]/2.0;
bounds[2*d+1] = prob_hi[d] - dx[d]/2.0;
}
AllPrint() << "Loading file"<< std::endl;
auto polyData = ReadPolyData(inputFilename);
// Construct the surface .
vtkNew<vtkSurfaceReconstructionFilter> surfaceReconstruction;
surfaceReconstruction->SetInputData(polyData);
surfaceReconstruction->SetSampleSpacing(dx[0]);
surfaceReconstruction->Update();
//Getting output
vtkNew<vtkImageResize> scale;
scale->SetInputConnection(surfaceReconstruction->GetOutputPort());
vtkNew<vtkImageBSplineInterpolator> interp;
interp->SetSplineDegree(3);
scale->SetInterpolator(interp);
scale->SetResizeMethodToOutputSpacing();
scale->SetOutputSpacing(dx[0], dx[1], dx[2]);
scale->CroppingOn();
scale->SetCroppingRegion(bounds);
scale->Update();
// Get output Array
vtkImageData* data = scale->GetOutput();
float* dataIt = (float*)data->GetScalarPointer();
//Copy into another array as required...
}