GridInsideHole.cpp

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/*
 * GridInsideHole.c:
 * from a convex set of points, figure out a point that for sure lies inside the profile.
 */
 
#include <math.h>
 
#include "./triangle.h"
#include "../Exp/exp.h"
 
#undef M_PI
#define M_PI 3.141592653589793238462643
 
int GridInsideHole(double* px0,double* py0,int n,double* x,double* y){
 
   double flag=0.0;
   double xA,xB,xC,xD,xE;
   double yA,yB,yC,yD,yE;
 
   /*Take first and last vertices: */
   xA=x[0];
   yA=y[0];
   xB=x[n-1];
   yB=y[n-1];
 
   /*Figure out middle of segment [A B]: */
   xC=(xA+xB)/2;
   yC=(yA+yB)/2;
 
   /*D and E are on each side of segment [A B], on the median line between segment [A  B], 
    *at an angle of 10 degree (less than the minimum 30 enforced by the quality of the mesh: */
   xD=xC+tan(10./180.*M_PI)*(yC-yA);
   yD=yC+tan(10./180.*M_PI)*(xA-xC);
   xE=xC-tan(10./180.*M_PI)*(yC-yA);
   yE=yC-tan(10./180.*M_PI)*(xA-xC);
 
   /*Either E or D is inside profile (x,y): */
   IsInPolySerial(&flag,&xD,&yD,1,x,y,n,2);
   /*FIXME: used to be 'flag' and not '!flag', check*/
   if(!flag){
      /*D is inside the poly: */
      *px0=xD;
      *py0=yD;
   }
   else{
      /*E is inside the poly: */
      *px0=xE;
      *py0=yE;
   }
   return 1;
}