title: how to use `dgrid3d` in `gnuplot` correctly?
body: <p>I've got a data file which contains a bunch of <code>x</code>, <code>y</code> and <code>z</code> <strong>points</strong>. I'd like to use <code>gnuplot</code> to plot out these points <code>with pm3d</code>but this requires me to turn on <code>set dgrid 10,10,1</code> (the number should be different). THe problem is that my data gets warped (the points don't lay on the <code>pm3d</code>surface when I plot them out together). </p>
  
  <p>How should I use <code>dgrid3d</code>? The points are generated from a <code>c++</code> program, so I can choose the x and y spacing myself.</p>
  
  <p>My data looks like this:</p>
  
  <pre><code># X    Y    Z
    1    2    3
    2    2    4
    ...
  </code></pre>
  
  <p>I'd like it to be a colored surface that runs through these points in 3D space. The <code>x</code> and <code>y</code> data is spaced evenly, while the <code>z</code> data is a function of <code>x</code> and <code>y</code> points.</p>