vtk lights in Mayavi

[Williams, Darren]

Hi Everyone. 

I have learned that vtk has both headlights located at

infinity and source lights located at some position. 

mylight = vtk.vtkLight()

It is apparent that Mayavi includes the "headlight"

option. But I'd like to also insert a "source" light

emanating from an x,y,z position in the scene.

This should in principle be possible by adding a vtk light 

and converting it to an "actor" for insertion.

I'm looking for help with the procedure for doing this. 

Thanks (Anyone).

Darren Williams

[Prabhu Ramachandran]

Just to keep the answer public,  here are a few possibly useful pointers.

1. You can access the lights used in a scene like so::

from mayavi import mlab

s = mlab.test_plot3d()

print(s.scene.light_manager.lights)

You can then set the properties of the lights as you see fit.  You can also add/remove new lights:

from tvtk.pyface.light_manager import CameraLight

c = CameraLight(s.scene)

s.scene.light_manager.lights.append(c)

By default the lights are at infinity (they are not positional lights) and this can be changed like so::

from mayavi import mlab
g = mlab.test_plot3d()

g.scene.light_manager.lights[0].source.positional = True

Hope this helps.  The VTK Lights documentation is worth reading:

https://vtk.org/doc/nightly/html/classvtkLight.html#details

cheers,

Prabhu

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[Williams, Darren]

Ok, thanks, but the following commands:

myscene = Instance(MlabSceneModel, ())

camera_light0 = self.myscene.scene_editor.light_manager.lights[0]

camera_light0.color = (1,0,0)

camera_light0.source.positional = True

camera_light0.position=(10,0,10)

   

yields a red light shining on a spherical surface, but the position/direction of the 

light is always the same, no matter what I change the coordinates in last statement to. 

What am I doing wrong?

---

From: ets-...@googlegroups.com <ets-...@googlegroups.com> on behalf of Prabhu Ramachandran <pra...@enthought.com>
Sent: Saturday, October 16, 2021 8:20 AM
To: Williams, Darren <dmw...@psu.edu>
Cc: Enthought Tool Suite users <ets-...@googlegroups.com>
Subject: Re: [ets-users] vtk lights in Mayavi

 

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[Prabhu Ramachandran]

Hi Darren,

Here is an example, without a reproducible example I cannot quite tell.  By default mayavi uses the "raymond" mode which has 4 active lights.  The vtk mode is simpler.  

from mayavi import mlab
g = mlab.test_plot3d()

g.scene.light_manager.light_mode = 'vtk'

l0 = g.scene.light_manager.lights[0]
l0.source.positional = True

l0.source.position = 1, 0, 1

g.scene.render()

Did you see the documentation link I shared, there are many methods that you can try like setting the cone angle, focal point, attenuation, and also switch the light between a camera light and a scene light.

cheers,

Prabhu

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