The water molecule

This shows the method of making the water molecule. The molecule is is shown in the figure below.

Note that the method of adding objects is very repetitive. As a result, all of the repetitive code may be put into a general function that will do all that is required for making the molecule. The code is provided below. As usual, it builds upon the previous code.

#! /usr/bin/python

from vtk import *

from math import cos, sin

pi = 3.141592

###### Functions for making objects ################

#---------------------------------------------

# Make a sphere of a certain radius, position

# and color. This will represent an atom.

#---------------------------------------------

def makeSphere(radius, position, color):

# create the object to be drawn

sphere = vtkSphereSource()

sphere.SetRadius( radius )

sphere.SetThetaResolution(30)

sphere.SetPhiResolution(30)

sphere.SetCenter(position[0], position[1], position[2])

# Convert the sphere into polygons

sphereMapper = vtkPolyDataMapper()

sphereMapper.SetInput(sphere.GetOutput())

#Create an actor for the sphere 

sphereActor = vtkActor()

sphereActor.SetMapper(sphereMapper)

(sphereActor.GetProperty()).SetColor(color[0], color[1], color[2])

return sphereActor

#---------------------------------------------

# Make a cylinder of a certain radius, position

# orientation and color. This will represent an

# atom.

#---------------------------------------------

def makeCylinder(radius, height, position, color, rotation):

# create the object to be drawn

cylinder = vtkCylinderSource()

cylinder.SetRadius(radius)

cylinder.SetHeight(height)

cylinder.SetResolution(30)

cylinder.SetCenter(position[0], position[1], position[2])

# Convert the sphere into polygons

cylinderMapper = vtkPolyDataMapper()

cylinderMapper.SetInput(cylinder.GetOutput())

#Create an actor for the sphere 

cylinderActor = vtkActor()

cylinderActor.SetMapper(cylinderMapper)

(cylinderActor.GetProperty()).SetColor(color[0], color[1], color[2])

cylinderActor.RotateX(rotation[0])

cylinderActor.RotateY(rotation[1])

cylinderActor.RotateZ(rotation[2])

return cylinderActor

###### The Main Program Starts Here ################

# create a rendering window and renderer

ren = vtkRenderer()

renWin = vtkRenderWindow()

renWin.AddRenderer(ren)

renWin.SetSize(300,300)

renWin.StereoCapableWindowOn()

iren = vtkRenderWindowInteractor()

iren.SetRenderWindow(renWin)

x_ox = 0; y_ox = 0; z_ox = 0

x_h1 = 10; y_h1 = 0; z_h1 = 0

x_h2 = 10*cos(104.5*pi/180); y_h2 = 10*sin(104.5*pi/180); z_h2 = 0

# Create the molecules

ren.AddActor( makeSphere(5, [x_ox, y_ox, z_ox], [1,0,0]) ) # Oxygen

ren.AddActor( makeSphere(2, [x_h1, y_h1, z_h1], [1,1,1]) ) # Hydrogen

ren.AddActor( makeSphere(2, [x_h2, y_h2, z_h2], [1,1,1]) ) # Hydrogen

# Create the connectors

ren.AddActor( makeCylinder(1, 10, [0, 5, 0], [0,0,1], [0,0,-90]) ) 

ren.AddActor( makeCylinder(1, 10, [0, 5, 0], [0,0,1], [0,0, 14.5]) ) 

# enable user interface interactor

iren.Initialize()

iren.Start()