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Polygon.cpp
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Polygon.cpp
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#include <cmath>
#include "Edge.h"
#include "Triangle.h"
#include "Polygon.h"
Polygon::Polygon( double** _verts, int _n, int quadOrder ) {
int i;
n = _n;
verts = new double*[n];
edges = new Edge*[n];
tris = new Triangle*[n];
for( i = 0; i < n; i++ ) {
verts[i] = new double[2];
verts[i][0] = _verts[i][0];
verts[i][1] = _verts[i][1];
}
GenOrigin();
for( i = 0; i < n; i++ ) {
edges[i] = new Edge( verts[i], verts[(i+1)%n] );
tris[i] = new Triangle( verts[i], verts[(i+1)%n], origin, quadOrder );
}
}
Polygon::~Polygon() {
int i;
for( i = 0; i < n; i++ ) {
delete[] verts[i];
delete edges[i];
delete tris[i];
}
delete[] verts;
delete[] edges;
delete[] tris;
}
#define R2_TOL 1.0e-8
int Polygon::AddPoint( double** pts, int np, double* pt ) {
int i;
for( i = 0; i < np; i++ ) {
if( (pts[i][0] - pt[0])*(pts[i][0] - pt[0]) + (pts[i][1] - pt[1])*(pts[i][1] - pt[1]) < R2_TOL ) {
return np;
}
}
pts[np][0] = pt[0];
pts[np][1] = pt[1];
return np + 1;
}
#define MAX_POLY 10
Polygon* Polygon::Intersection( Polygon* poly ) {
int vi, vj, iOffset = -1, jOffset = -1, pSize = 0;
double **polyVerts;
double ijInt[2], jiInt[2];
Polygon* intPoly = NULL;
bool allInside;
polyVerts = new double*[MAX_POLY];
for( vi = 0; vi < MAX_POLY; vi++ ) {
polyVerts[vi] = new double[2];
}
/* find the first point of polygon j inside polygon i (assume clockwise orientation of vertices) */
allInside = true;
for( vj = 0; vj < poly->n; vj++ ) {
if( IsInside( poly->verts[vj] ) && !IsInside( poly->verts[(poly->n+vj-1)%poly->n] ) ) {
jOffset = vj;
allInside = false;
break;
}
if( vj == poly->n ) {
jOffset = 0;
break;
}
}
/* polygon j is entirely inside polygon i */
if( allInside ) {
intPoly = new Polygon( poly->verts, poly->n, tris[0]->order );
for( vi = 0; vi < MAX_POLY; vi++ ) {
delete[] polyVerts[vi];
}
delete[] polyVerts;
return intPoly;
}
/* find the first point of polygon i inside polygon j (assume clockwise orientation of vertices) */
allInside = true;
for( vi = 0; vi < n; vi++ ) {
if( poly->IsInside( verts[vi] ) && !poly->IsInside( verts[(n+vi-1)%n] ) ) {
iOffset = vi;
allInside = false;
break;
}
if( vi == n ) {
iOffset = 0;
break;
}
}
/* polygon i is entirely inside polygon j */
if( allInside ) {
intPoly = new Polygon( verts, n, tris[0]->order );
for( vi = 0; vi < MAX_POLY; vi++ ) {
delete[] polyVerts[vi];
}
delete[] polyVerts;
return intPoly;
}
/* no verts of either polygon inside the other */
if( iOffset == -1 && jOffset == -1 ) {
for( vi = 0; vi < MAX_POLY; vi++ ) {
delete[] polyVerts[vi];
}
delete[] polyVerts;
return NULL;
}
/* start adding polygon i's verts to the new polygon */
if( iOffset > -1 ) {
for( vi = 0; vi < n; vi++ ) {
if( !poly->IsInside( verts[(vi+iOffset)%n] ) )
break;
pSize = AddPoint( polyVerts, pSize, verts[(vi+iOffset)%n] );
}
}
/* add the ij intersection point to the new polygon */
if( edges[(n+vi+iOffset-1)%n]->Intersection( poly->edges[(poly->n+jOffset-1)%poly->n], ijInt ) ) {
pSize = AddPoint( polyVerts, pSize, ijInt );
}
/* start adding polygon j's verts to the new polygon */
if( jOffset > -1 ) {
for( vj = 0; vj < poly->n; vj++ ) {
if( !IsInside( poly->verts[(vj+jOffset)%poly->n] ) )
break;
pSize = AddPoint( polyVerts, pSize, poly->verts[(vj+jOffset)%poly->n] );
}
}
/* add the ji intersection point to the new polygon */
if( poly->edges[(poly->n+vj+jOffset-1)%poly->n]->Intersection( edges[(n+iOffset-1)%n], jiInt ) ) {
pSize = AddPoint( polyVerts, pSize, jiInt );
}
/* now instantiate the new polygon */
if( pSize > 2 ) {
intPoly = new Polygon( polyVerts, pSize, tris[0]->order );
}
for( vi = 0; vi < MAX_POLY; vi++ ) {
delete[] polyVerts[vi];
}
delete[] polyVerts;
return intPoly;
}
/* reqires that polygon vertices are consistently ordered clockwise */
bool Polygon::IsInside( double* pt ) {
int i;
double edgeCrossOrig, edgeCrossPt;
Triangle* tri;
for( i = 0; i < n; i++ ) {
/* is the point shared by both polygons? */
if( (verts[i][0] - pt[0])*(verts[i][0] - pt[0]) + (verts[i][1] - pt[1])*(verts[i][1] - pt[1]) < R2_TOL ) {
return true;
}
edgeCrossOrig = tris[i]->CrossProduct( 2 );
tri = new Triangle( verts[i], verts[(i+1)%n], pt, 2 );
edgeCrossPt = tri->CrossProduct( 2 );
delete tri;
if( edgeCrossOrig*edgeCrossPt < 0.0 ) {
return false;
}
}
return true;
}
void Polygon::GenOrigin() {
int i;
origin[0] = origin[1] = 0.0;
for( i = 0; i < n; i++ ) {
origin[0] += verts[i][0];
origin[1] += verts[i][1];
}
origin[0] /= n;
origin[1] /= n;
}
double Polygon::Area() {
double area = 0.0;
int tri_i;
for( tri_i = 0; tri_i < n; tri_i++ ) {
area += tris[tri_i]->area;
}
return area;
}
void Polygon::Print() {
int vi;
for( vi = 0; vi < n; vi++ ) {
cout << "[" << verts[vi][0] << ", " << verts[vi][1] << "]" << endl;
}
}