Discrepancy between vtkPLYReader and vtkSTLReader when streaming.

Development
1

Hi everyone,

I was wondering why there seems to be a difference in usage of vtkMemoryResourceStream with both PLY & STL readers. the former requires explicit declaration of turning on the stream despite setting the buffer which isn’t the case for the latter whereby setting the buffer is sufficient.

// data is NSData (as I'm working on macOS)

vtkSmartPointer<vtkMemoryResourceStream> memoryStream = vtkSmartPointer<vtkMemoryResourceStream>::New();
memoryStream->SetBuffer([data bytes], [data length]);


// PLY
//---------------------------------------------------------
vtkSmartPointer<vtkPLYReader> reader = vtkSmartPointer<vtkPLYReader>::New();
reader->SetStream(memoryStream);
reader->ReadFromInputStreamOn();     // without this, it will fail to read
reader->Update();
polydata = reader->GetOutput();


// STL  (this works) 
// + there no such API to explicitly ReadFromInputStreamOn
//---------------------------------------------------------

vtkSmartPointer<vtkSTLReader> reader = vtkSmartPointer<vtkSTLReader>::New();
reader->SetStream(memoryStream);
reader->Update();
polydata = reader->GetOutput();

why is this the case?