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TGraphDelaunay2D.cxx
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1// @(#)root/hist:$Id: TGraphDelaunay2D.cxx,v 1.00
2// Author: Olivier Couet, Luke Jones (Royal Holloway, University of London)
3
4/*************************************************************************
5 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *
6 * All rights reserved. *
7 * *
8 * For the licensing terms see $ROOTSYS/LICENSE. *
9 * For the list of contributors see $ROOTSYS/README/CREDITS. *
10 *************************************************************************/
11
12#include "TGraph2D.h"
13#include "TGraphDelaunay2D.h"
14
15
16
17/** \class TGraphDelaunay2D
18 \ingroup Graphs
19TGraphDelaunay2D generates a Delaunay triangulation of a TGraph2D.
20The algorithm used for finding the triangles is based on [CDT](https://github.com/artem-ogre/CDT),
21a C++ library for generating constraint or conforming Delaunay triangulations.
22
23The ROOT::Math::Delaunay2D class provides a wrapper for using
24the **CDT** library.
25
26This implementation provides large improvements in terms of computational performances
27compared to the legacy one available in TGraphDelaunay, and it is by default
28used in TGraph2D. The old, legacy implementation can be still used when calling
29`TGraph2D::GetHistogram` and `TGraph2D::Draw` with the `old` option.
30
31Definition of Delaunay triangulation (After B. Delaunay):
32For a set S of points in the Euclidean plane, the unique triangulation DT(S)
33of S such that no point in S is inside the circumcircle of any triangle in
34DT(S). DT(S) is the dual of the Voronoi diagram of S. If n is the number of
35points in S, the Voronoi diagram of S is the partitioning of the plane
36containing S points into n convex polygons such that each polygon contains
37exactly one point and every point in a given polygon is closer to its
38central point than to any other. A Voronoi diagram is sometimes also known
39as a Dirichlet tessellation.
40
41\image html tgraph2d_delaunay.png
42
43[This applet](http://www.cs.cornell.edu/Info/People/chew/Delaunay.html)
44gives a nice practical view of Delaunay triangulation and Voronoi diagram.
45*/
46
47/// TGraphDelaunay2D normal constructor
49 TNamed("TGraphDelaunay2D","TGraphDelaunay2D"),
50 fGraph2D(g),
51 fDelaunay((g) ? g->GetN() : 0, (g) ? g->GetX() : nullptr, (g) ? g->GetY() : nullptr, (g) ? g->GetZ() : nullptr ,
52 (g) ? g->GetXmin() : 0, (g) ? g->GetXmax() : 0,
53 (g) ? g->GetYmin() : 0, (g) ? g->GetYmax() : 0 )
54
55{}
56
#define g(i)
Definition RSha256.hxx:105
Graphics object made of three arrays X, Y and Z with the same number of points each.
Definition TGraph2D.h:41
TGraphDelaunay2D(const TGraphDelaunay2D &)=delete
The TNamed class is the base class for all named ROOT classes.
Definition TNamed.h:29