"""A MayaVi example of how to generate a 2D structured points dataset
using numpy arrays.  Also shown is a way to visualize this data with
mayavi2.  The script can be run like so:

  $ mayavi2 -x structured_points2d.py

Alternatively, it can be run as:

  $ python structured_points2d.py
  
Author: Prabhu Ramachandran <prabhu at aero dot iitb dot ac dot in>

Copyright (c) 2007, Enthought, Inc.
License: BSD style.
"""

# The following *optional* two lines allow a user to call this script
# as either `python script.py` or `mayavi2 script.py`.  These two
# lines must be placed before any other mayavi imports.
from enthought.mayavi.scripts import mayavi2
mayavi2.standalone(globals())

from numpy import arange, sqrt
from scipy import special
from enthought.tvtk.api import tvtk

# Generate the scalar values.
x = (arange(50.0)-25)/2.0
y = (arange(50.0)-25)/2.0
r = sqrt(x[:,None]**2+y**2)
z = 5.0*special.j0(r)  # Bessel function of order 0

# Make the tvtk dataset.
# tvtk.ImageData is identical and could also be used here.
spoints = tvtk.StructuredPoints(origin=(-12.5,-12.5,0),
                                spacing=(0.5,0.5,1),
                                dimensions=(50,50,1))
# Transpose the array data due to VTK's implicit ordering. VTK assumes
# an implicit ordering of the points: X co-ordinate increases first, Y
# next and Z last.  We flatten it so the number of components is 1.
spoints.point_data.scalars = z.T.flatten()
spoints.point_data.scalars.name = 'scalar'

# Uncomment the next two lines to save the dataset to a VTK XML file.
#w = tvtk.XMLImageDataWriter(input=spoints, file_name='spoints2d.vti')
#w.write()

# Now view the data.
def view():
    from enthought.mayavi.sources.vtk_data_source import VTKDataSource
    from enthought.mayavi.filters.warp_scalar import WarpScalar
    from enthought.mayavi.filters.poly_data_normals import PolyDataNormals
    from enthought.mayavi.modules.surface import Surface

    mayavi.new_scene()
    src = VTKDataSource(data = spoints)
    mayavi.add_source(src)
    mayavi.add_filter(WarpScalar())
    mayavi.add_filter(PolyDataNormals())
    s = Surface()
    mayavi.add_module(s)

view()