Gradient of color

[Eugene]

Hi, I'm trying to create a gradient shade for a sphere with alpha(0.1). May I know how can it be done in vizard? Currently, the shade is constant throughout the sphere.

My objective is to create a blue atmosphere around the earth that is darker on both ends.

Alternatively, I'm also trying to generate a glowing effect around the earth to improve but not sure how can I do it. Appreciate your advice.

The Earth object is a OSGB file created in 3ds Max.

code:

import viz
import vizshape
import vizfx

viz.setMultiSample(8)
viz.fov(60)
viz.go()

earth = viz.addChild('earth.osgb')
earth.setScale(0.01,0.01,0.01)
earth.setPosition(0,1,0)
earth.addAction( vizact.spin(0,1,0,20) )
vizfx.addDirectionalLight(euler=(-45,90,45), color=viz.WHITE)


earthAT = vizshape.addSphere(radius=2.2,slices=60,stacks=60, axis=vizshape.AXIS_Y)
earthAT.setPosition([0, 1, 0])
earthAT.color(viz.AZURE)
earthAT.alpha(0.15)


Thank you.