163 lines
5 KiB
C++
163 lines
5 KiB
C++
/*************************************************************************/
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/* triangulate.cpp */
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/*************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* http://www.godotengine.org */
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/*************************************************************************/
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/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur. */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/*************************************************************************/
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#include "triangulate.h"
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real_t Triangulate::get_area(const Vector<Vector2> &contour)
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{
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int n = contour.size();
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const Vector2 *c=&contour[0];
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real_t A=0.0;
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for(int p=n-1,q=0; q<n; p=q++)
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{
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A+= c[p].cross(c[q]);
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}
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return A*0.5;
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}
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/*
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is_inside_triangle decides if a point P is Inside of the triangle
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defined by A, B, C.
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*/
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bool Triangulate::is_inside_triangle(real_t Ax, real_t Ay,
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real_t Bx, real_t By,
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real_t Cx, real_t Cy,
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real_t Px, real_t Py)
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{
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real_t ax, ay, bx, by, cx, cy, apx, apy, bpx, bpy, cpx, cpy;
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real_t cCROSSap, bCROSScp, aCROSSbp;
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ax = Cx - Bx; ay = Cy - By;
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bx = Ax - Cx; by = Ay - Cy;
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cx = Bx - Ax; cy = By - Ay;
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apx= Px - Ax; apy= Py - Ay;
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bpx= Px - Bx; bpy= Py - By;
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cpx= Px - Cx; cpy= Py - Cy;
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aCROSSbp = ax*bpy - ay*bpx;
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cCROSSap = cx*apy - cy*apx;
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bCROSScp = bx*cpy - by*cpx;
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return ((aCROSSbp >= 0.0) && (bCROSScp >= 0.0) && (cCROSSap >= 0.0));
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};
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bool Triangulate::snip(const Vector<Vector2> &p_contour,int u,int v,int w,int n,const Vector<int>& V)
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{
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int p;
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real_t Ax, Ay, Bx, By, Cx, Cy, Px, Py;
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const Vector2 *contour=&p_contour[0];
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Ax = contour[V[u]].x;
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Ay = contour[V[u]].y;
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Bx = contour[V[v]].x;
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By = contour[V[v]].y;
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Cx = contour[V[w]].x;
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Cy = contour[V[w]].y;
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if ( CMP_EPSILON > (((Bx-Ax)*(Cy-Ay)) - ((By-Ay)*(Cx-Ax))) ) return false;
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for (p=0;p<n;p++)
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{
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if( (p == u) || (p == v) || (p == w) ) continue;
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Px = contour[V[p]].x;
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Py = contour[V[p]].y;
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if (is_inside_triangle(Ax,Ay,Bx,By,Cx,Cy,Px,Py)) return false;
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}
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return true;
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}
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bool Triangulate::triangulate(const Vector<Vector2> &contour,Vector<int> &result)
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{
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/* allocate and initialize list of Vertices in polygon */
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int n = contour.size();
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if ( n < 3 ) return false;
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Vector<int> V;
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V.resize(n);
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/* we want a counter-clockwise polygon in V */
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if ( 0.0 < get_area(contour) )
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for (int v=0; v<n; v++) V[v] = v;
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else
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for(int v=0; v<n; v++) V[v] = (n-1)-v;
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int nv = n;
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/* remove nv-2 Vertices, creating 1 triangle every time */
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int count = 2*nv; /* error detection */
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for(int v=nv-1; nv>2; )
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{
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/* if we loop, it is probably a non-simple polygon */
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if (0 >= (count--))
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{
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//** Triangulate: ERROR - probable bad polygon!
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return false;
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}
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/* three consecutive vertices in current polygon, <u,v,w> */
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int u = v ; if (nv <= u) u = 0; /* previous */
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v = u+1; if (nv <= v) v = 0; /* new v */
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int w = v+1; if (nv <= w) w = 0; /* next */
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if ( snip(contour,u,v,w,nv,V) )
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{
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int a,b,c,s,t;
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/* true names of the vertices */
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a = V[u]; b = V[v]; c = V[w];
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/* output Triangle */
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result.push_back( a );
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result.push_back( b );
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result.push_back( c );
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/* remove v from remaining polygon */
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for(s=v,t=v+1;t<nv;s++,t++)
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V[s] = V[t];
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nv--;
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/* resest error detection counter */
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count = 2*nv;
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}
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}
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return true;
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}
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