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Recently, i have read a paper named "as rigid as possible surface modeling", when I turned to its project web page, the author told us it had been implemented in CGAL. So with having a try mind, I decide to study this lib.

let us introduce how to install CGAL on ubuntu:

For instance in debian/Ubuntu, use apt-get in the following way:

sudo apt-get install libcgal-dev

To get the demos use

sudo apt-get install libcgal-demo

After installing, let us try to program the first example in qt.

.pro file looks like below:

#-------------------------------------------------## Project created by QtCreator 2016-01-28T13:29:40##-------------------------------------------------QT       += coreQT       -= guiTARGET = TestCGALCONFIG   += consoleCONFIG   -= app_bundleTEMPLATE = appSOURCES += main.cppLIBS += -L/lib64 -lgmp -lCGALQMAKE_CXXFLAGS += -frounding-math -O3

the content of main.cpp is as follow:

#include 
   
    #include 
    
     typedef CGAL::Simple_cartesian
     
       Kernel;typedef Kernel::Point_2 Point_2;typedef Kernel::Segment_2 Segment_2;int main(){  Point_2 p(1,1), q(10,10);  std::cout << "p = " << p << std::endl;  std::cout << "q = " << q.x() << " " << q.y() << std::endl;  std::cout << "sqdist(p,q) = "            << CGAL::squared_distance(p,q) << std::endl;  Segment_2 s(p,q);  Point_2 m(5, 9);  std::cout << "m = " << m << std::endl;  std::cout << "sqdist(Segment_2(p,q), m) = "            << CGAL::squared_distance(s,m) << std::endl;  std::cout << "p, q, and m ";  switch (CGAL::orientation(p,q,m)){  case CGAL::COLLINEAR:    std::cout << "are collinear\n";    break;  case CGAL::LEFT_TURN:    std::cout << "make a left turn\n";    break;  case CGAL::RIGHT_TURN:    std::cout << "make a right turn\n";    break;  }  std::cout << " midpoint(p,q) = " << CGAL::midpoint(p,q) << std::endl;  return 0;}
     
    
   

the result is shown in the pic: