Mayavi: How can I flip the Z-axis of a scene?

Question

I am trying to flip Z-axis in the mayavi volumetric 3D plot. I figured how to rotate the camera etc, but that is not what I want. I just want to flip the direction of Z-axis. Without manipulating the data itself

#Minimum working example

import numpy as np
from mayavi import mlab

x, y, z = np.ogrid[-5:5:64j, -5:5:64j, -5:5:64j] #Generate XYZ
data = np.arange(x.shape[0])
x = x.ravel()
y = y.ravel()
z = z.ravel()
mlab.points3d(x, y, z, data) #Produce volumetric plot
mlab.axes(xlabel='X', ylabel='Y', zlabel='Z') #Display axis
mlab.orientation_axes()
mlab.show()

Just have a look at this page: https://stackoverflow.com/questions/2051744/reverse-y-axis-in-pyplot — Sheldore, Aug 29 '18 at 11:31
@Bazingaa but this staff is about matplotlib. We are talking about Mayavi here — Artemii Novoselov, Aug 29 '18 at 11:34
Ok, I thought similar features exist also for mayavi as well. — Sheldore, Aug 29 '18 at 11:36
@Bazingaa I have tried, but even if they do, it is not that straight forward — Artemii Novoselov, Aug 29 '18 at 11:37
I found `mlab.axes(ranges = [...])` where one can specify the x, y, z axes ranges but it just seem to reverse the axis tick labels. Since you plot is symmetric across [001[ plane, it's hard to see the effect of reversing the z values in this command — Sheldore, Aug 29 '18 at 11:56
@Bazingaa I checked, indeed it just switches the labels, not the actual plot — Artemii Novoselov, Aug 29 '18 at 12:45

Joe · Accepted Answer · 2018-08-29T14:06:50.757

Could you please explain what you mean using non-symmetric data using this example. Do you want negative z to be at the top side? And why does rotating the camera not produce the result you want to see?

You can add the code from the macro editor (explained below).

import numpy as np
from mayavi import mlab

x, y, z = np.ogrid[-5:5:64j, -5:5:64j, -5:5:64j] #Generate XYZ
data = np.arange(x.shape[0])
x = x.ravel()
y = y.ravel()
z = z.ravel()

# Recorded script from Mayavi2
from numpy import array
try:
    engine = mayavi.engine
except (AttributeError, NameError):
    from mayavi.api import Engine
    engine = Engine()
    engine.start()
if len(engine.scenes) == 0:
    engine.new_scene()
# -------------------------------------------
scene = engine.scenes[0]
scene.scene.camera.position = [20.68813263960946, 20.334388554161922, 20.518300376103046]
scene.scene.camera.focal_point = [0.24373197555541992, 0.24373197555541992, 0.25]
scene.scene.camera.view_angle = 30.0
scene.scene.camera.view_up = [-0.41179533881878827, -0.4046701524210215, 0.81649658092772626]
scene.scene.camera.clipping_range = [15.729834995160559, 58.864284541884331]
scene.scene.camera.compute_view_plane_normal()
scene.scene.render()

mlab.points3d(x, y, z, data) #Produce volumetric plot
mlab.axes(xlabel='X', ylabel='Y', zlabel='Z') #Display axis
mlab.orientation_axes()

mlab.show()

If you really can set the view you want manually I would just do that. To get the correct coordinates to pass to mlab.view() read them from the interactive plot while rotating the scene:

Agreed, your data example is better for visualization. Yes, indeed I what negative Z on top. I played around with camera settings, but never managed to get how to set camera as I want — Artemii Novoselov, Aug 29 '18 at 12:49
Were you able to manually rotate the image to get the result you want to see? Could you paste an image? — Joe, Aug 29 '18 at 13:03
but are those the same I use in mlab.view? Becasue I see that view can operate azimuth, elevation, distance, etc. While scen has attributes position, view angle, view up etc. Not really clear to me, which one to use — Artemii Novoselov, Aug 29 '18 at 13:53
Yes, I also noticed that. `view_angle` might be `azimuth`, and maybe `view_up` is a unit vector that can be used to calculate `elevation`. — Joe, Aug 29 '18 at 13:55
But you could use the camera settings directly, instead of using ``view`. I will add code in a minute. — Joe, Aug 29 '18 at 13:56

Mayavi: How can I flip the Z-axis of a scene?

1 Answers1