title: How to increase smoothness of spheres3d in rgl
body: <p>When I use <code>rgl::spheres3d()</code>, the rendered spheres have clunky facetted edges.</p>
  
  <pre><code>spheres = data.frame(x = c(1,2,3), y = c(1,3,1),
                       color = c("#992222" , "#222299", "#229922"))
  open3d()
  spheres3d(spheres$x, spheres$y, radius = 1, color = spheres$color)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/EQgE4.png" rel="noreferrer"><img src="https://i.stack.imgur.com/EQgE4.png" alt="enter image description here"></a></p>
  
  <p>Setting <code>material3d(smooth = TRUE, line_antialias = TRUE)</code> does not improve this.  Increasing the radius does not help either.  Is there any way to increase the smoothness with which they are drawn?</p>