R - Add symbols in labels from a plot3D
<p>I have tried inserting text3D but the rgl package masks it, below an example:</p>

<pre><code>plot3d(x1, y1, z1, cex=1.5, size=4, type="l",col="red" )
text3D(2, -5, 0, labels = expression(theta[1]), add = TRUE, adj = 1)
</code></pre>

<p>How can I do it?</p>