Draw cubes with colour intensity with Python

Question

I'd like to know how to plot many cubes with Python. For each cube I have its coordinates (Xmin, Xmax, Ymin, Ymax, Zmin, Zmax) and its value to draw the cube according this value. In fact what I really want to draw voxels.

I've seen some libraries like matplotlib, mayavi, OpenGL, but I don't know which of these libraries to use and how. I think it's not difficult because a cube is an easy regular figure, but I can't reach the solution.

As I have to plot many cubes, it would be good to set the extent, not to represent all the cubes, and I know that mayavi has this option.

score 1 · Answer 1 · answered Nov 24 '14 at 18:39

1

In mayavi, you can use set the glyph type from a list of predefined shapes with mlab.points3d.

points = mlab.points3d(px, py, pz, mode='cube')

This will plot the cube at each point, at the center of the cube.

You can also plot glyphs and then later change the source type with

points.glyph.glyph_source.glyph_source = points.glyph.glyph_source.glyph_dict['cube_source']

(You can also do this in the pipeline menu)

The scale_factor argument will allow you to change the cube size.

It's an inconvenient way to plot voxel by voxel data, but it will do what you asked for.

answered Nov 24 '14 at 18:39

aestrivex

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Thank you. I've thought of this solution, but I would like that the cube sides were adjacent. I could do it if I could insert side size, but I only can insert a scale_factor. – Pablo Nov 27 '14 at 07:53
I think that in mayavi this is the "correct" solution with some experimentation with the scale factor, particularly if that scale never has to change. Alternately it may be possible to do some vtk programming that sets the size of the gylphs directly. Any other solution in mayavi (rather than vtk directly) that I can think of will involve allocating a large number of vtk objects which can quickly get quite unwieldy and slow. – aestrivex Dec 01 '14 at 15:17
Any idea how to change the orientation of the points3D glyphs? For instance in terms of a set of unit vectors perpendicular to the faces? – kevinkayaks Nov 16 '17 at 02:07

score 1 · Answer 2 · answered Aug 06 '19 at 06:08

In mayavi you can plot the faces of a cube with a mesh, for instance.

from mayavi import mlab
import numpy as np

def cube_faces(xmin, xmax, ymin, ymax, zmin, zmax):
    faces = []

    x,y = np.mgrid[xmin:xmax:3j,ymin:ymax:3j]
    z = np.ones(y.shape)*zmin
    faces.append((x,y,z))

    x,y = np.mgrid[xmin:xmax:3j,ymin:ymax:3j]
    z = np.ones(y.shape)*zmax
    faces.append((x,y,z))

    x,z = np.mgrid[xmin:xmax:3j,zmin:zmax:3j]
    y = np.ones(z.shape)*ymin
    faces.append((x,y,z))

    x,z = np.mgrid[xmin:xmax:3j,zmin:zmax:3j]
    y = np.ones(z.shape)*ymax
    faces.append((x,y,z))

    y,z = np.mgrid[ymin:ymax:3j,zmin:zmax:3j]
    x = np.ones(z.shape)*xmin
    faces.append((x,y,z))

    y,z = np.mgrid[ymin:ymax:3j,zmin:zmax:3j]
    x = np.ones(z.shape)*xmax
    faces.append((x,y,z))

    return faces

def mlab_plt_cube(xmin,xmax,ymin,ymax,zmin,zmax):
    faces = cube_faces(xmin,xmax,ymin,ymax,zmin,zmax)
    for grid in faces:
        x,y,z = grid
        mlab.mesh(x,y,z,opacity=0.4)

mlab_plt_cube(0,1,0,1,0,1)
mlab.show()

I'd bet there's a one-liner for the cube_faces function. I'm too tired to contemplate it right this second though.

Draw cubes with colour intensity with Python

2 Answers2