We draw a color cube in Mayavi

Greetings, habravchane!

Today I want to tell you about what Mayavi is and what ~~they wash~~ it ~~down with~~ .

Mayavi is a cross-platform application for visualizing scientific data (and not only). It is distributed under the BSD license, which allows its use in commercial applications.

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What can?

Build 2D and 3D models based on scalar / vector data
Open VTK, PLOT3D files
Save the results of the render in various graphic formats
May even render MRI results (Magnetic Resonance Imaging)

You can work with it in three ways:
1) Work directly in the Mayavi interface.
2) Upload / upload ready data to Mayavi.
3) Write a Python script in which you can set all the desired features for Mayavi.

After launching the stand-alone version, we get this nice window:

The screen is divided into 4 parts:

Top left stores objects
In the lower left part, the properties of objects change.
Render occurs at the top right
In the lower right corner there is a terminal.

Let me explain why you need a terminal:

Create some object and select it in the list of objects. Select and, without releasing the left mouse button, drag it to the terminal window. We get something like
<enthought.mayavi.modules.surface.Surface object at 0x0DADE5D0>
Now we will write:
explore(_)
and then a window will appear with all the parameters of the object. This is a very useful thing that can help in learning and creating your own scripts. I recognized some properties of objects in this way, without finding them in the documentation. In this window, the Drag'N'Drop rule works in the same way.

There are quite a lot of examples in the Mayavi documentation, which generally explain what to do and how.

I will try to describe the rake that I stepped on. For the most part, they will be concerned with embedding the Mayavi frame in the PyQt widget (or PySide, which I have already written about .

Do not read the documentation from pdf files. True, do not read. Waste of time.
Do not replace the habit of class constructors. Create any methods to which variables / objects will be passed, which are then used for rendering in the update_plot () functions.
Try to pinpoint what you want to see. TVTK classes may not support the functions that the mlab classes have (for example, Volume).
When working with numpy arrays, cast them to type float32, because By default, a float64 array is created on a 64-bit system, with which Mayavi will not work.
I will give one example of building a regular cube with embedding it in the PyQT widget.
1. # To embed the PyQt4 widget, set the ETS_TOOLKIT variable to qt4.
2. import os
3. os . environ [ 'ETS_TOOLKIT' ] = 'qt4'
4. from PySide import QtGui, QtCore
6. from enthought. mayavi import mlab
7. from enthought. tvtk . api import tvtk
8. from enthought. tvtk . pyface . api import scene
9. from numpy import arange, nonzero, float32, min , max , median, copy , random , shape
10. from numpy. core . numeric import ravel
12. from enthought. traits . api import HasTraits, Instance, on_trait_change, \
13. Int, dict
14. from enthought. traits . ui . api import View, Item
15. from enthought. mayavi . core . ui . api import MayaviScene, MlabSceneModel, \
16. Sceneeditor
18. #The actual visualization
19. class Visualization ( HasTraits ) :
20. scene = Instance ( MlabSceneModel, ( ) )
21. view = View ( Item ( 'scene' ,
22. editor = SceneEditor ( scene_class = MayaviScene ) ,
23. # Instead of MayaviScene, you can write just Scene
24. # and then we get a clean window without a toolbar.
25. height = 250 ,
26. width = 300 ,
27. show_label = False )
28. resizable = true
29. )
31. needUpdate = None
33. def takePlotParametres ( self , grid ) :
34. self . grid = grid
36. # The clf () method clears the current scene. It MUST NOT be called in the update_plot () method.
37. self . scene . mlab . clf ( )
38. self . needUpdate = True
40. self . update_plot ( )
42. @on_trait_change ( 'scene.activated' )
43. def update_plot ( self ) :
44. # This method is called for rendering.
45. # Everything you need to draw is written here and nowhere else
47. # While there is no data, draw the standard model
48. if not self . needUpdate :
49. self . scene . mlab . test_points3d ( )
50. else :
51. # Here we write all our rice paddles
53. # Everything that is drawn through mlab needs to be called.
54. # as self.scene.mlab. *, otherwise the Mayavi window is out of control
55. # and starts to draw everything in a separate window.
56. # opacity greatly influences rendering performance!
57. surf = self . scene . mlab . pipeline . surface ( self . grid , opacity = 1 )
59. # You can also display the internal grid by uncommenting the lines.
60. #edges = mlab.pipeline.extract_edges (surf)
61. #edgesSurf = mlab.pipeline.surface (edges)
62. # edgesSurf.actor.property.interpolation = 'flat'
64. # Remove the interpolation of the surface color of the cube. Let each cell be clearly visible.
65. surf. actor . property . interpolation = 'flat'
67. self . scene . mlab . orientation_axes ( )
68. self . scene . background = ( 0 , 0 , 0 )
69. self . scene . mlab . colorbar ( orientation = 'vertical' )
72. ################################################## ##############################
73. # Widget into which we embed the scene. Use it as a regular PyQt widget.
75. class MayaviQWidget ( QtGui. QWidget ) :
76. def __init__ ( self , parent = None ) :
77. QtGui QWidget . __init__ ( self , parent )
78. layout = QtGui. QVBoxLayout ( self )
79. layout. setMargin ( 0 )
80. layout. setSpacing ( 0 )
81. self . visualization = Visualization ( )
83. # Ideally, it is here that you can call the takePlotParametres method with initial data, but this is not necessary
84. # self.visualization.takePlotParametres ()
86. # The edit_traits method generates the window in which the scene is built.
87. # This is the window you need to make Qt'shnym, for which we call the method .control
88. self . ui = self . visualization . edit_traits ( parent = self ,
89. kind = 'subpanel' ) . control
90. layout. addWidget ( self . ui )
91. self . ui . setParent ( self )
93. def create_cube ( self ) :
94. grid = self . createGrid ( )
96. self . visualization . takePlotParametres ( grid )
98. def createGrid ( self ) :
99. x, y, z = ( 10 , 10 , 10 )
101. # Create a grid for our cube
102. grid = tvtk. RectilinearGrid ( )
104. # It is important to bring data to float32, since on 64-bit OS, numpy creates float64 by default,
105. # and Mayavi can't work with him.
106. # Create random data
107. scalars = float32 ( random . random ( ( x * y * z ) ) )
109. # scalars is the value that will be stored in each cell of our cube.
110. # It is for this value that the color of the cell surface is determined.
111. grid. point_data . scalars = scalars
112. grid. point_data . scalars . name = 'scalars'
114. grid. dimensions = ( x, y, z )
115. grid. x_coordinates = float32 ( arange ( x ) )
116. grid. y_coordinates = float32 ( arange ( y ) )
117. grid. z_coordinates = float32 ( arange ( z ) )
119. return grid
121. if __name__ == "__main__" :
122. # It is important not to create a new application, but to use
123. # which Mayavi creates automatically, otherwise you will kill all the Traits signals / slots,
124. # and we just do not need it.
125. # To get the link, call the instance () method.
126. # Do not write out of habit QtGui.QApplication (sys.argv) .instance (),
127. # I already attacked this rake.
128. app = QtGui. QApplication . instance ( )
130. container = QtGui. QWidget ( )
131. container. setWindowTitle ( "Hello Habrahabr!" )
132. layout = QtGui. QVBoxLayout ( container )
134. mayavi_widget = MayaviQWidget ( )
136. button = QtGui. QPushButton ( 'Create cube' )
137. button. clicked . connect ( mayavi_widget. create_cube )
139. layout. addWidget ( mayavi_widget )
140. layout. addWidget ( button )
142. container. show ( )
144. app. exec_ ( )

Start and get this window:

Press the button and get a colored cube:

If you want to see something more scientific, you can take a look at it:

Well, you can also create something futuristic (inside one parallelepiped with the included inner edges):

On it I complete the topic. If you want to see something else, then I am waiting for comments.

PS A little later I will write a topic about Chaco. I hope you are just as interesting to read about him?

Source: https://habr.com/ru/post/115170/

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We draw a color cube in Mayavi

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