title: How to add points to scatter3d?
body: <p>I am trying to plot two sets of points in the same 3D scatterplot using interactive "rgl" package for R</p>
  
  <p>this is the data:</p>
  
  <pre><code>&gt; head(tsne_train)
             X1         X2          X3
  2   18.940912 -46.761145 -56.1818708
  4   17.768953  68.678871   0.8070582
  6   -2.440751 -53.021051  55.0437596
  7   44.740812  -2.347877 -54.1501468
  8  -87.924687  15.354890 -30.1806330
  12  21.991465  38.406572 -33.0551010`
  
  &gt; head(tsne_test)
            X1         X2          X3
  1   1.585156  71.568255    7.438958
  3  62.204021  -3.817038  -37.609328
  5   5.422276 -21.855152   66.865478
  9  21.223133 -29.763255 -107.832779
  10  9.037427 -62.816717   65.560664
  11 24.775047 -51.820532   57.106795
  </code></pre>
  
  <p>this is what I tried so far:</p>
  
  <pre><code>scatter3d( x=tsne_train[,1],y=tsne_train[,2],z=tsne_train[,3],
            groups = train$Result,
            surface=F, grid = T, ellipsoid = FALSE,sphere.size = 1.5,
            surface.col = c("red", "orange", "green"),fogtype="none",
            axis.col=c("black","black","black"))
  </code></pre>
  
  <p>produces:
     <a href="https://i.stack.imgur.com/wfdeA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wfdeA.png" alt="enter image description here"></a></p>
  
  <p>and</p>
  
  <pre><code>scatter3d(x=tsne_test[,1],y=tsne_test[,2],z=tsne_test[,3], groups = test$Result,
                  surface=F, grid = T, ellipsoid = FALSE,sphere.size = 1.5,
                  col = c("purple", "blue", "cyan"), fogtype="none",
                  axis.col=c("black","black","black"))
  </code></pre>
  
  <p>produces:
     <a href="https://i.stack.imgur.com/ABfXh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ABfXh.png" alt="enter image description here"></a></p>
  
  <p>I want all the points in one scatterplot but preserving the color grouping (6 colors in total). Kind of like overlaying plot 2 over plot 1</p>
  
  <p>Using spheres3d to add more points to a plot leads to this mess:</p>
  
  <pre><code>spheres3d(x=tsne_test[,1],y=tsne_test[,2],z=tsne_test[,3],
           surface=F, grid = T,
           col = c("purple", "blue", "cyan"), sphere.size = 3,
           axis.col=c("black","black","black"))
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/FFqSI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FFqSI.png" alt="enter image description here"></a></p>
  
  <p>this does not preserve the green/red/orange points from plot #1, the axes aren't visible and the position of the points looks off since plot #2 looks nothing like it. Maybe I am just using spheres3d wrong?</p>