Custom data colors in a surface plot

[Ion V. <vas...@pc...>]

Hi,

I'd like to customize the data color in a surface plot using a color 
gradient going from a QColor cMax to a QColor cMin (like the one in the 
default standard color implementation, going from red to blue).

I've tried to follow the approach from the enrichements example. Using the 
following code I only get an uniform green color:

void Graph3D::setColor()
{	
   Qwt3D::ColorVector cv;

   QColor cMax=QColor(green); // color for the max data
   QColor cMin=QColor (red); // color for the min data

   unsigned int size=255;
   double dsize = size;

   int r1=cMax.red();
   int r2=cMin.red();

   double stepR = abs(r1-r2)/dsize;

   int g1=cMax.green();
   int g2=cMin.green();

   double stepG = abs(g1-g2)/dsize;

   int b1=cMax.blue();
   int b2=cMin.blue();

   double stepB = abs(b1-b2)/dsize;

  RGBA rgb;
  for (unsigned int i=0; i<size; i++)
	{
     rgb.r = r1-i*stepR;
	rgb.g = g1-i*stepG;
	rgb.b = b1-i*stepB;

     cv.push_back(rgb);	
     }

	StandardColor* col = new StandardColor(sp);
	col->setColorVector(cv);
	
	sp->setDataColor(col);
	sp->updateData();
	sp->updateGL();
}

Could anyone give me a hint, please?
Thanks in advance,
Ion