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3.2.9 Cutting sample ¶

The last common thing which I want to show in this section is how one can cut off points from plot. There are 4 mechanism for that.

• You can set one of coordinate to NAN value. All points with NAN values will be omitted.
• You can enable cutting at edges by SetCut function. As result all points out of bounding box will be omitted.
• You can set cutting box by SetCutBox function. All points inside this box will be omitted.
• You can define cutting formula by SetCutOff function. All points for which the value of formula is nonzero will be omitted. Note, that this is the slowest variant.

Below I place the code which demonstrate last 3 possibilities:

int sample(mglGraph *gr)
{
  mglData a,c,v(1); mgls_prepare2d(&a); mgls_prepare3d(&c); v.a[0]=0.5;
  gr->SubPlot(2,2,0); gr->Title("Cut on (default)");
  gr->Rotate(50,60);  gr->Light(true);
  gr->Box();  gr->Surf(a,"","zrange -1 0.5");

  gr->SubPlot(2,2,1); gr->Title("Cut off");   gr->Rotate(50,60);
  gr->Box();  gr->Surf(a,"","zrange -1 0.5; cut off");

  gr->SubPlot(2,2,2); gr->Title("Cut in box");  gr->Rotate(50,60);
  gr->SetCutBox(mglPoint(0,-1,-1), mglPoint(1,0,1.1));
  gr->Alpha(true);  gr->Box();  gr->Surf3(c);
  gr->SetCutBox(mglPoint(0), mglPoint(0));  // switch it off

  gr->SubPlot(2,2,3); gr->Title("Cut by formula");  gr->Rotate(50,60);
  gr->CutOff("(z>(x+0.5*y-1)^2-1) & (z>(x-0.5*y-1)^2-1)");
  gr->Box();  gr->Surf3(c); gr->CutOff(""); // switch it off
  return 0;
}