title: Plot two datasets on the same graph with gnuplot. One with dgrid3d, the other one without
body: <p>I'm trying to plot two data sets with gnuplot. They are both (x, y, z) triplets. They are not arranged on a grid. I want to plot one of them using <code>dgrid3d</code> and <code>pm3d</code>. On top of that I want to overlay the other data set but as just scattered points. </p>
  
  <p>To give a more concrete example: I am trying to plot the effect of a cylinder approaching a surface. I want to plot the response of the surface and that's where <code>dgrid3d</code> comes in handy. On top of that, I want to plot the position of the cylinder and I have its circumference as points.</p>
  
  <p>I used:</p>
  
  <pre><code>set dgrid3d 100,100,4
  set pm3d
  splot "dataset1" with pm3d, "dataset2" with dots
  </code></pre>
  
  <p>The data set has about 100x100 points, arranged on a near-square, so 100,100 works best here. No matter how I plot the second data set, it always ends up being a square of the same dimensions as the cylinder, instead of a nice circle. When I turn <code>dgrid3d</code> off, I can plot the second data set on its own and the result is a nice circumference of the cylinder.</p>
  
  <p>So my question is: is it possible to plot a 3D graph using two data sets, one using <code>dgrid3d</code> and the other one not using it?</p>