Hello everybody,
I'm working on a project where I have to plot many points on a spectrogram (I'm plotting level curves of a 3d function), and so far I've implemented all the features I need for this program, but when I want to use the feature "Print" to print the plot to pdf or any other format and try to zoom in far enough I get a loss in quality of the type you can see on the following picture. I've tried to change the resolution of the QwtPlotRenderer object in dpi to big numbers (like 1200 or so) but it doesn't really change the "smoothness" of the curves and I always seem to get those "spikes" on the curves.
My question is, is there any way I can "postpone" this behaviour, that is, since this is a plot I know I will end up having those "spikes", but can I increase the number of safe zooms on this plot?

Capturar.jpgCapturar.jpg

Also, I implemented the QwtRasterData as in the Spectrogram exemple that comes with qwt:

Qt Code: 
  1. class SpectrogramData: public QwtRasterData
  2. {
  3.     const double u;
  4. public:
  5.     SpectrogramData(double externalValue, double cCenter, double cInterval) :
  6.         u(externalValue)
  7.     {
  8.         setInterval( Qt::XAxis, QwtInterval(-1.5, 1.5) ); 
  9.         setInterval( Qt::YAxis, QwtInterval(-1.5, 1.5) ); 
  10.         setInterval( Qt::ZAxis, QwtInterval(cCenter-cInterval/2, cCenter+cInterval/2) );
  11.     }
  12.  
  13.     virtual double value( double x, double y ) const
  14.     {
  15.         const double v1 = -0.5*(x*x+y*y);
  16.         const double v2 = -(1-u)/(qSqrt((x-u)*(x-u)+y*y));
  17.         const double v3 = -u/(qSqrt((x+1-u)*(x+1-u)+y*y));
  18.         return v1+v2+v3;
  19.     }
  20. };
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And I have read something about
Qt Code: 
  1. setRenderThreadCount(0);
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but it doesn't seem to change anything so far...
Thank you,
Hope it wasn't too confusing