3.7.10 Cont projection sample

Functions contz, conty, contx draw contour lines on plane perpendicular to corresponding axis. One of possible application is drawing projections of 3D field. The sample code is:

int sample(mglGraph *gr)
{
  mglData c;  mgls_prepare3d(&c);
  gr->Title("Cont[XYZ] sample");  gr->Rotate(50,60);
  gr->Box();  gr->ContX(c.Sum("x"),"",-1);
  gr->ContY(c.Sum("y"),"",1); gr->ContZ(c.Sum("z"),"",-1);
  return 0;
}