title: How to visualize data with Qt QwtPlot3D
body: <p>I have a problem using <code>Qt</code>+<code>QwtPlot3D</code> library.</p>
  
  <p>I need to visualize the data. The data is a simple matrix 5x5. Values are float numbers.</p>
  
  <p>For example like this:</p>
  
  <pre><code>0  0    0    0     0
  0  4,5  0,5  1,5  -2
  0  0,5  2    0,5   0
  0  0,5  0,5  0,45  0
  0  0    0    0     0
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/Je1x1.png" alt="This matrix visualisation"></p>
  
  <p>I try out all examples. I understand to use library I should create class with reloaded <code>operator</code> with inheritance from class <code>Qwt3D::Fucntion</code>.</p>
  
  <pre><code>double operator (double x, double y);
  </code></pre>
  
  <p>This way is not for me becase I have no <code>z = f(x,y)</code>, I have only coordinates.</p>
  
  <hr>
  
  <p>In the <a href="http://qwtplot3d.sourceforge.net/web/navigation/manual_frame.html" rel="nofollow noreferrer" title="QwtPlot3D  Manual">official manual</a> I found this function:</p>
  
  <pre><code>bool loadFromData(double **data, unsigned int columns, unsigned int rows, 
                    double minx, double maxx, double miny, double maxy)
  </code></pre>
  
  <p>But there is no example or sample how to draw the plot using this function.</p>
  
  <p>Can you help me to find the way to draw my matrix in Qt?</p>