polytrimon.cpp

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#include <cassert>
#include <algorithm>
using namespace std;

#include <indextable.h>
#include <point.h>
#include <polytrimon.h>


void polytrimon::vsprint() const 
{
  cout << "vs: ";
  for (uint i=0; i<vs.size(); ++i)
    cout << vs[i] << " ";
  cout << endl;
}

void polytrimon::colorsprint() const
{
  cout << "colors: ";
  for (uint i=0; i<colors.size(); ++i)
    cout << i << "=" << colors[i] << " ";
  cout << endl;
}

void polytrimon::vyprint() const
{
  cout << "vy: ";
  for (uint i=0; i<vy.size(); ++i)
    cout << vy[i] << " ";
  cout << endl;
}

void polytrimon::colorsinit()
{
  uint iend = pts.size();
  uint i = 1; 

  colors.resize(pts.size());

  // Assume clockwise ordering of points
  // from top.

  // Let top be black.
  colors[0] = 1; 

  for ( ; pts[i].y <= pts[i-1].y; )
  {
    colors[i] = 1;

    ++i;

    if (i==iend)
      break;
  }

//cout << SHOW(i) << " " SHOW(pts[i]) << endl;

  for ( ; i<iend; ++i)
    colors[i] = 2;

  // Taken out multicolored state
  //colors[0] = 3;
}

void polytrimon::vyinit()
{
  int i = 0;
  int k = pts.size()-1;

  for ( ; i!=k; )
  {
    if ( pts[i].y> pts[k].y )
      vy.push_back(i++);
    else
      vy.push_back(k--);
  }
  vy.push_back(i);
}

polytrimon::polytrimon
(  
  vector< point2<float> > const & pts_ 
)
  : pts(pts_)
{
  assert(pts.size()>2);
   
  colorsinit();

  vyinit();
}

boolc polytrimon::ispointvisible() const
{
  if (vs.size()<3)
    return false;

//  Points of different colors are always visible.  
//  So no need to use this test in this case.
assert(colors[vs[0]]==colors[vs[1]]);

  uint a;
  uint b;

  // Moving down the right hand side the vector
  // needs to point left. Moving down the left
  // hand side the vector needs to point right.
  if (colors[vs[1]]==2)
  {
    a = vs[2];
    b = vs[1];
  }
  else
  {
    a = vs[1];
    b = vs[2];
  }

  uint x = vs[0];
 
  point2<float> X = pts[x] - pts[a];
  point2<float> W = pts[b] - pts[a];
  point2<float> W90(-W.y,W.x);
   
  if ( X.x*W90.x + X.y*W90.y > 0 )
    return true; 

  return false;
}