[vtkusers] VTK 3D Structured Grid Problem

[Andrea Gavana]

Hello NG,

      I'm working with a 3D structured grid in VTK, using Python and the 
wrapping vtkpython. What I do is as follows:

1) Using Fortran, via a Python-Fortran interface, I read a 3D grid coming from 
another application. This 3D grid is now on a matrix with shape (8,nx*ny*nz), 
every cell is identified by 8 coordinates (first index of the matrix) and I 
have globally nx*ny*nz cells (second index of the matrix);

2) Using the pyvtk module, I write this matrix on a binary file;

3) I load the file using vtkStructuredGridReader().

So, my process is as follows:

# CODE BEGIN

vtks = VtkData(StructuredGrid([2*nx,2*ny,2*nz],MYMATRIX)
vtks.tofile('myfile','binary')
filename = 'myfile.vtk'

reader = vtkpython.vtkStructuredGridReader()
reader.SetFileName(filename)

mapsurface = vtkpython.vtkDataSetMapper()
mapsurface.SetInput(reader.GetOutput())
mapedge = vtkpython.vtkDataSetMapper()
mapedge.SetInput(reader.GetOutput())

# CODE END

Next I use the usual rendering/interacting command in order to display the 3D 
grid. The problem is that I have A LOT of cells in my grid, so this process is 
fairly slow...

Is there a way to create a VTKStructuredGrid object directly from a matrix 
(without passing through a file)?

I've tried also this way:

# CODE BEGIN

pts = vtk.vtkPoints()
pts.SetNumberOfPoints(8*nx*ny*nz)
a = vtk.vtkStructuredGrid()
a.SetDimensions(2*nx,2*ny,2*nz)
	
idx = 0
for i in range(0,2*nz):
	for j in range(0,2*ny):
		for i in range(0,2*nx):
		    pts.SetPoint(idx, nanna[0,idx], nanna[1,idx], nanna[2,idx])
		    idx = idx + 1	

a.SetPoints(pts)
mapsurface = vtk.vtkDataSetMapper()
meshGeom = vtk.vtkStructuredGridGeometryFilter()
meshGeom.SetInput(a)
meshGeom.SetExtent(0, nx-1, 0, ny-1, 0, nz-1)
mapsurface.SetInput(meshGeom.GetOutput())

actsurface = vtkpython.vtkActor()
actsurface.SetMapper(mapsurface)

# CODE END

But I get 2 problems:

1) Doing 3 for loops with a lot of cells is also slow (I can have also a 
million cells)
2) The only thing I get is a 3D plot of the points, not a surface or a 
wireframe, and I do not know why...

Is there anyone that can provide me a small piece of code to do it in Python? 
I'm not really an expert on VTK/Python, I just started learning...

Thanks for every suggestion.

Andrea.