title: R rgl distance between axis ticks and tick labels
body: <p>I am plotting some point data using plot3d().
  I would like to bring my y axis tick labels a little closer to my y axis tick marks.</p>
  
  <p>The best way I can think of doing this is to</p>
  
  <p>1) plot the data first, without drawing the axes</p>
  
  <p>2) call on axis3d() to draw the y axis and tick marks but suppress labels from being drawn.</p>
  
  <p>3) query the current position of each tick mark in 3D space. Store positions in a vector.</p>
  
  <p>4) use mtext3d() to add labels at positions based on an adjustment to the vector</p>
  
  <p>I am having a problem at step 3. I don't know how to query the position of each tick mark.
  par3d() allows you to query a number of graphical parameters, is there something similar I can use to get the position each y axis tick?</p>
  
  <p>Am I approaching this wrong? Probably.</p>
  
  <p>Here is an example piece of code, without text added for y axis labels....</p>
  
  <pre><code>require(rgl)
  x &lt;- rnorm(5)
  y &lt;- rnorm(5)
  z &lt;- rnorm(5)
  open3d()
  plot3d(x,y,z,axes=F,xlab="",ylab="",zlab="")
  par3d(ignoreExtent=TRUE)
  par3d(FOV=0)
  par3d(userMatrix=rotationMatrix(0,1,0,0))
  axis3d('y',nticks=5,labels = FALSE)
  par3d(zoom=1)
  par3d(windowRect=c(580,60,1380,900))
  </code></pre>