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* triangulate.c |
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* |
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* Adapted by Greg Ward on 1/23/14. |
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* Copyright 2014 Anyhere Software. All rights reserved. |
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* Fixes for polygons with seams/holes and co-linear vertices added |
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* by Nathaniel Jones on 12/21/16. |
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* Copyright 2016 Anyhere Software. All rights reserved. |
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* |
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*/ |
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polySnip(const Vert2_list *contour, int u, int v, int w, int n, int *V) |
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{ |
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int p; |
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double Ax, Ay, Bx, By, Cx, Cy, Px, Py; |
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double Ax, Ay, Bx, By, Cx, Cy, Px, Py, cross; |
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Ax = contour->v[V[u]].mX; |
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Ay = contour->v[V[u]].mY; |
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Cx = contour->v[V[w]].mX; |
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Cy = contour->v[V[w]].mY; |
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if ( EPSILON > (((Bx-Ax)*(Cy-Ay)) - ((By-Ay)*(Cx-Ax))) ) return false; |
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cross = ((Bx - Ax)*(Cy - Ay)) - ((By - Ay)*(Cx - Ax)); |
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if (EPSILON > cross) return EPSILON > -cross ? -1 : false; /* Negative if colinear points */ |
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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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if( (p == u) | (p == v) | (p == w) ) continue; |
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Px = contour->v[V[p]].mX; |
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Py = contour->v[V[p]].mY; |
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if ((Px == Ax && Py == Ay) || (Px == Bx && Py == By) || |
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(Px == Cx && Py == Cy)) continue; /* Handle donuts */ |
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if (insideTriangle(Ax,Ay,Bx,By,Cx,Cy,Px,Py)) return false; |
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} |
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{ |
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/* allocate and initialize list of Vertices in polygon */ |
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int nv, m, u, v, w, count; |
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int nv, m, u, v, w, count, result; |
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int *V; |
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if ( contour->nv < 3 ) return false; |
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/* we want a counter-clockwise polygon in V */ |
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if ( 0.0 < Area(contour) ) |
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if ( 0.0 < polyArea(contour) ) |
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for (v=0; v<contour->nv; v++) V[v] = v; |
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else |
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for(v=0; v<contour->nv; v++) V[v] = (contour->nv-1)-v; |
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for(m=0, 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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if (0 >= count--) |
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{ |
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/* Triangulate: ERROR - probable bad polygon! */ |
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/* Triangulate: ERROR - probable bad polygon */ |
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return false; |
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} |
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v = u+1; if (nv <= v) v = 0; /* new v */ |
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w = v+1; if (nv <= w) w = 0; /* next */ |
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if ( polySnip(contour,u,v,w,nv,V) ) |
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result = polySnip(contour, u, v, w, nv, V); |
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if (result > 0) /* successfully found a triangle */ |
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{ |
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int a,b,c,s,t; |
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int a,b,c; |
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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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(*cb)(contour, a, b, c); |
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if (!(*cb)(contour, a, b, c)) return false; |
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m++; |
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} |
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if (result) /* successfully found a triangle or three consecutive colinear points */ |
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{ |
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int s,t; |
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/* remove v from remaining polygon */ |
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for(s=v,t=v+1;t<nv;s++,t++) V[s] = V[t]; nv--; |
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/* resest error detection counter */ |
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/* reset error detection counter */ |
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count = 2*nv; |
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} |
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} |
