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Changing the looks of the visual objects created
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-------------------------------------------------
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Adding color or size variations
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The color of the objects created by a plotting function can be specified
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explicitly using the 'color' keyword argument of the function. This color
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is than applied uniformly to all the objects created.
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If you want to vary the color across your visualization, you need to
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specify scalar information for each data point. Some functions try to
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guess this information: these scalars default to the norm of the vectors,
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for functions with vectors, or to the z elevation for functions where is
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meaningful, such as :func:`surf` or :func:`barchart`.
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This scalar information is converted into colors using the colormap, or
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also called LUT, for Look Up Table. The list of possible colormaps is::
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accent flag hot pubu set2
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autumn gist_earth hsv pubugn set3
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black-white gist_gray jet puor spectral
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blue-red gist_heat oranges purd spring
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blues gist_ncar orrd purples summer
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bone gist_rainbow paired rdbu winter
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brbg gist_stern pastel1 rdgy ylgnbu
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bugn gist_yarg pastel2 rdpu ylgn
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bupu gnbu pink rdylbu ylorbr
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cool gray piyg rdylgn ylorrd
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copper greens prgn reds
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dark2 greys prism set1
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The easiest way to choose the colormap most adapted to your visualization
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is to use the GUI (as described in the next paragraph). The dialog
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to set the colormap can be found in the `Colors and legends` node.
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The scalar information can also be displayed in many different ways.
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For instance it can be used to adjust the size of glyphs positioned at
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**A caveat: Clamping: relative or absolute scaling**
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Given six points positionned on a line with interpoint spacing 1::
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x = [1, 2, 3, 4, 5, 6]
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y = [0, 0, 0, 0, 0, 0]
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If we represent a scalar varying from 0.5 to 1 on this dataset::
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s = [.5, .6, .7, .8, .9, 1]
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We represent the dataset as spheres, using :func:`points3d`, and the
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scalar is mapped to diameter of the spheres::
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from enthought.mayavi import mlab
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pts = mlab.points3d(x, y, z, s)
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By default the diameter of the spheres is not 'clamped', in other
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words, the smallest value of the scalar data is represented as a null
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diameter, and the largest is proportional to inter-point distance.
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The scaling is only relative, as can be seen on the resulting
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.. image:: clamping_on.jpg
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This behavior gives visible points for all datasets, but may not be
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desired if the scalar represents the size of the glyphs in the same
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unit as the positions specified.
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In this case, you shoud turn auto-scaling off by specifying the desired
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pts = mlab.points3d(x, y, z, s, scale_factor=1)
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.. image:: clamping_off.jpg
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In earlier versions of Mayavi (up to 3.1.0 included), the glyphs are
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not auto-scaled, and as a result the visualization can seem empty
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due to the glyphs being very small. In addition the minimum diameter of
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the glyphs is clamped to zero, and thus the glyph are not scaled
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absolutely, unless you specifie::
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pts.glyph.glyph.clamping = False
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:More representations of the attached scalars or vectors:
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There are many more ways to represent the scalar or vector information
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attached to the data. For instance, scalar data can be 'warped' into a
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displacement, e.g. using a `WarpScalar` filter, or the norm of scalar
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data can be extract to a scalar component that can be visualized using
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iso-surfaces with the `ExtractVectorNorm` filter.
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Changing the scale and position of objects
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Each mlab function takes an `extent` keyword argument, that allows to set
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its (x, y, z) extents. This give both control on the scaling in the
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different directions and the displacement of the center. Beware that when
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you are using this functionality, it can be useful to pass the same
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extents to other modules visualizing the same data. If you don't, they
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will not share the same displacement and scale.
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.. _mlab-changing-objects-interactively:
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Changing object properties interactively
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Mayavi, and thus mlab, allows you to interactively modify your
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The Mayavi pipeline tree can be displayed by clicking on the mayavi icon
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in the figure's toolbar, or by using :func:`show_pipeline` mlab command.
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One can now change the visualization using this dialog by double-clicking
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on each object to edit its properties, as described in other parts of
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this manual, or add new modules or filters by using this icons on the
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pipeline, or through the right-click menus on the objects in the
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.. image:: images/pipeline_and_scene.png
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In addition, for every object returned by a mlab function,
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``this_object.edit_traits()`` brings up a dialog that can be used to
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interactively edit the object's properties. If the dialog doesn't show up
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when you enter this command, please see :ref:`running-mlab-scripts`.
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docs/source/mayavi/mlab_changing_object_looks.rst
