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/****************************************************************************
* VCGLib o o *
* Visual and Computer Graphics Library o o *
* _ O _ *
* Copyright(C) 2004-2016 \/)\/ *
* Visual Computing Lab /\/| *
* ISTI - Italian National Research Council | *
* \ *
* All rights reserved. *
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
* This program is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License (http://www.gnu.org/licenses/gpl.txt) *
* for more details. *
* *
****************************************************************************/
#ifndef __VCGLIB_PLANAR_POLYGON_TESSELLATOR
#define __VCGLIB_PLANAR_POLYGON_TESSELLATOR
#include <assert.h>
#include <vcg/space/segment2.h>
#include <vcg/math/random_generator.h>
namespace vcg {
/** \addtogroup space */
/*@{*/
/**
A very simple earcut tessellation of planar 2D polygon.
Input: a vector or Point2<>
Output: a vector of faces as a triple of indices to the input vector
*/
template <class ScalarType>
bool Cross( const Point2<ScalarType> & p00,
const Point2<ScalarType> & p01,
const Point2<ScalarType> & p10,
const Point2<ScalarType> & p11)
{
Point2<ScalarType> vec0 = p01-p00;
Point2<ScalarType> vec1 = p11-p10;
if ( ( vec0^ (p11-p00)) * ( vec0^ (p10 - p00)) >=0) return false;
if ( ( vec1^ (p01-p10)) * ( vec1^ (p00 - p10)) >=0) return false;
return true;
}
template <class S>
bool Intersect(size_t cur , int v2, std::vector<int> & next, std::vector<Point2<S> > & points2){
for(size_t i = 0; i < points2.size();++i)
if( (next[i]!=-1) && (i!=cur))
if( Cross(points2[cur], points2[v2],points2[i],points2[next[i]]))
return true;
return false;
}
template <class POINT_CONTAINER>
void TessellatePlanarPolygon2( POINT_CONTAINER & points2, std::vector<int> & output){
typedef typename POINT_CONTAINER::value_type Point2x;
typedef typename Point2x::ScalarType S;
// tessellate
// first very inefficient implementation
std::vector<int> next,prev;
for(size_t i = 0; i < points2.size(); ++i) next.push_back((i+1)%points2.size());
for(size_t i = 0; i < points2.size(); ++i) prev.push_back((i+points2.size()-1)%points2.size());
int v1,v2;
// check orientation
S orient = 0.0;
for(size_t i = 0 ; i < points2.size(); ++i){
v1 = next[i];
v2 = next[v1];
orient+= (points2[v1] - points2[0]) ^ (points2[v2] - points2[0]);
}
orient = (orient>0)? 1.0:-1.0;
int cur = 0;
while(output.size()<3*(points2.size()-2)){
v1 = next[cur];
v2 = next[v1];
if( ( (orient*((points2[v1] - points2[cur]) ^ (points2[v2] - points2[cur]))) >= 0.0) &&
!Intersect(cur, v2,next,points2))
{
// output the face
output.push_back(cur);
output.push_back(v1);
output.push_back(v2);
// readjust the topology
next[cur] = v2;
prev[v2] = cur;
prev[v1] = -1;//unnecessary
next[v1] = -1;//unnecessary
}
else
do{cur = (cur+1)%points2.size();} while(next[cur]==-1);
}
}
/**
A very simple earcut tessellation of planar 2D polygon.
Input: a vector or Point3<>
Output: a vector of faces as a triple of indices to the input vector
*/
template <class POINT_CONTAINER>
void TessellatePlanarPolygon3( POINT_CONTAINER & points, std::vector<int> & output){
typedef typename POINT_CONTAINER::value_type Point3x;
typedef typename Point3x::ScalarType S;
Point3x n;
math::SubtractiveRingRNG rg;
size_t i12[2];
S bestsn = -1.0;
Point3x bestn,u,v;
for(size_t i =0; i < points.size();++i){
for(size_t j = 0; j < 2; ++j){ i12[j] = i; while(i12[j]==i) i12[j] = rg.generate(points.size()-1);}
n = (points[i12[0]]-points[i])^(points[i12[1]]-points[i]);
S sn = n.SquaredNorm();
if(sn > bestsn){ bestsn = sn; bestn = n;}
}
GetUV(n,u,v);
// project the coordinates
std::vector<Point2<S> > points2;
for(size_t i = 0; i < points.size(); ++i){
Point3x & p = points[i];
points2.push_back(Point2<S>(p*u,p*v));
}
TessellatePlanarPolygon2( points2,output);
}
/*@}*/
} // end namespace
#endif
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