- sphere(center=(0, 0, 0), size=1, **kwds)
- Return a plot of a sphere of radius size centered at
`(x,y,z)`.
INPUT:
- ``(x,y,z)`` - center (default: (0,0,0)
- ``size`` - the radius (default: 1)
EXAMPLES: A simple sphere::
sage: sphere()
Two spheres touching::
sage: sphere(center=(-1,0,0)) + sphere(center=(1,0,0), aspect_ratio=[1,1,1])
Spheres of radii 1 and 2 one stuck into the other::
sage: sphere(color='orange') + sphere(color=(0,0,0.3), \
center=(0,0,-2),size=2,opacity=0.9)
We draw a transparent sphere on a saddle.
::
sage: u,v = var('u v')
sage: saddle = plot3d(u^2 - v^2, (u,-2,2), (v,-2,2))
sage: sphere((0,0,1), color='red', opacity=0.5, aspect_ratio=[1,1,1]) + saddle
TESTS::
sage: T = sage.plot.plot3d.texture.Texture('red')
sage: S = sphere(texture=T)
sage: T in S.texture_set()
True