text: # -*- coding: utf-8 -*-
  """
  Demonstration of some of the shader programs included with pyqtgraph that can be 
  used to affect the appearance of a surface.
  """
  
  
  
  ## Add path to library (just for examples; you do not need this)
  import initExample
  
  from pyqtgraph.Qt import QtCore, QtGui
  import pyqtgraph as pg
  import pyqtgraph.opengl as gl
  
  app = QtGui.QApplication([])
  w = gl.GLViewWidget()
  w.show()
  w.setWindowTitle('pyqtgraph example: GL Shaders')
  w.setCameraPosition(distance=15, azimuth=-90)
  
  g = gl.GLGridItem()
  g.scale(2,2,1)
  w.addItem(g)
  
  import numpy as np
  
  
  md = gl.MeshData.sphere(rows=10, cols=20)
  x = np.linspace(-8, 8, 6)
  
  m1 = gl.GLMeshItem(meshdata=md, smooth=True, color=(1, 0, 0, 0.2), shader='balloon', glOptions='additive')
  m1.translate(x[0], 0, 0)
  m1.scale(1, 1, 2)
  w.addItem(m1)
  
  m2 = gl.GLMeshItem(meshdata=md, smooth=True, shader='normalColor', glOptions='opaque')
  m2.translate(x[1], 0, 0)
  m2.scale(1, 1, 2)
  w.addItem(m2)
  
  m3 = gl.GLMeshItem(meshdata=md, smooth=True, shader='viewNormalColor', glOptions='opaque')
  m3.translate(x[2], 0, 0)
  m3.scale(1, 1, 2)
  w.addItem(m3)
  
  m4 = gl.GLMeshItem(meshdata=md, smooth=True, shader='shaded', glOptions='opaque')
  m4.translate(x[3], 0, 0)
  m4.scale(1, 1, 2)
  w.addItem(m4)
  
  m5 = gl.GLMeshItem(meshdata=md, smooth=True, color=(1, 0, 0, 1), shader='edgeHilight', glOptions='opaque')
  m5.translate(x[4], 0, 0)
  m5.scale(1, 1, 2)
  w.addItem(m5)
  
  m6 = gl.GLMeshItem(meshdata=md, smooth=True, color=(1, 0, 0, 1), shader='heightColor', glOptions='opaque')
  m6.translate(x[5], 0, 0)
  m6.scale(1, 1, 2)
  w.addItem(m6)
  
  
  
  
  #def psi(i, j, k, offset=(25, 25, 50)):
      #x = i-offset[0]
      #y = j-offset[1]
      #z = k-offset[2]
      #th = np.arctan2(z, (x**2+y**2)**0.5)
      #phi = np.arctan2(y, x)
      #r = (x**2 + y**2 + z **2)**0.5
      #a0 = 1
      ##ps = (1./81.) * (2./np.pi)**0.5 * (1./a0)**(3/2) * (6 - r/a0) * (r/a0) * np.exp(-r/(3*a0)) * np.cos(th)
      #ps = (1./81.) * 1./(6.*np.pi)**0.5 * (1./a0)**(3/2) * (r/a0)**2 * np.exp(-r/(3*a0)) * (3 * np.cos(th)**2 - 1)
      
      #return ps
      
      ##return ((1./81.) * (1./np.pi)**0.5 * (1./a0)**(3/2) * (r/a0)**2 * (r/a0) * np.exp(-r/(3*a0)) * np.sin(th) * np.cos(th) * np.exp(2 * 1j * phi))**2 
  
  
  #print("Generating scalar field..")
  #data = np.abs(np.fromfunction(psi, (50,50,100)))
  
  
  ##data = np.fromfunction(lambda i,j,k: np.sin(0.2*((i-25)**2+(j-15)**2+k**2)**0.5), (50,50,50)); 
  #print("Generating isosurface..")
  #verts = pg.isosurface(data, data.max()/4.)
  
  #md = gl.MeshData.MeshData(vertexes=verts)
  
  #colors = np.ones((md.vertexes(indexed='faces').shape[0], 4), dtype=float)
  #colors[:,3] = 0.3
  #colors[:,2] = np.linspace(0, 1, colors.shape[0])
  #m1 = gl.GLMeshItem(meshdata=md, color=colors, smooth=False)
  
  #w.addItem(m1)
  #m1.translate(-25, -25, -20)
  
  #m2 = gl.GLMeshItem(vertexes=verts, color=colors, smooth=True)
  
  #w.addItem(m2)
  #m2.translate(-25, -25, -50)
      
  
  
  ## Start Qt event loop unless running in interactive mode.
  if __name__ == '__main__':
      import sys
      if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
          QtGui.QApplication.instance().exec_()
  