geometry_utilities.c

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#include "turtle.h"
#include "geometry.h"

int signum (long a){
if (a==0){
        return 0;
}else if(a>0) {
        return 1;
} else if(a<0){
        return -1;
}
return 1;
}

int signum_double (double a){
if (a==0.0){
        return 0;
}else if(a>0) {
        return 1;
} else if(a<0){
        return -1;
}
return 1;
}

int segment_intersection_occurence(LINE *L1,LINE *L2){
//int l;
double det,det1,det2;
double lambda1,lambda2;

det=-(L1->end->x-L1->begin->x)*(L2->end->y-L2->begin->y)+(L2->end->x-L2->begin->x)*(L1->end->y-L1->begin->y);
det1=-(L2->begin->x-L1->begin->x)*(L2->end->y-L2->begin->y)+(L2->end->x-L2->begin->x)*(L2->begin->y-L1->begin->y);
det2=(L1->end->x-L1->begin->x)*(L2->begin->y-L1->begin->y)-(L1->end->y-L1->begin->y)*(L2->begin->x-L1->begin->x);

if (det==0.0) {
        if ((det1==0) || (det2==0)) {
                return 2;
        }else {
                return 0;
        }
} else {
        lambda1=det1/det;
        lambda2=det2/det;
        if ((lambda1>0.0) && (lambda1<1.0) && (lambda2>0.0) && (lambda2<1.0)) {
                return 1;
        } else{
        return 0;
        }

}
return 0;

}

long query_freq_longvector(LONGVECTOR *lvector,long value){
long j,cnt;
cnt=0;
for (j=lvector->nl;j<=lvector->nh;j++){
        if (lvector->element[j]==value) cnt++;
}
return cnt;
}

int check_vertex_intersection_2_lines(long b1,long e1,long b2,long e2){
        if (signum(b1-e2)*signum(b1-b2)*signum(e1-e2)*signum(e1-b2)==0) {
                if ((signum(b1-e2)*signum(b1-e2)+signum(e1-b2)*signum(e1-b2))*(signum(b1-b2)*signum(b1-b2)+signum(e1-e2)*signum(e1-e2))==0)   {
                        return 2;
                }else {
                        return 1; 
                }

        }
        return 0;
}

int check_3_numbers(long a, long b, long c) {
//if (((a-b)*(a-b)+(a-c)*(a-c))==0) return 1;
        if ((a==b) && (a=c)) return TRUE;
        return FALSE;
}


double area2d(POINT *P1,POINT *P2, POINT *P3) {
        double area;


        area=(P1->x*(P3->y-P2->y)+P2->x*(P1->y-P3->y)+P3->x*(P2->y-P1->y))/2.0;
//      printf("x= %lf %lf %lf \n",P1->x,P2->x,P3->x);
//      printf("y= %lf %lf %lf \n",P1->y,P2->y,P3->y);
//      printf ("area= %lf",area);

        if (area<0.0) area=-area;

        return area;

}


double distance2D(POINT *P1,POINT *P2){
        return pow(pow(P1->x-P2->x,2.0)+pow(P1->y-P2->y,2.0),0.5);
}

long shared_edges(POLYGON *PO1, POLYGON *PO2, long no_intersection, long *l_po1, long *l_po2, double *dist_centroids){
long l,k,l_shared;
double distance;
int s;


l_shared=no_intersection;
s=0;

for(l=PO1->edge_indices->nl;l<=PO1->edge_indices->nh;l++){
        for(k=PO2->edge_indices->nl;k<=PO2->edge_indices->nh;k++){
                if (PO1->edge_indices->element[l]==PO2->edge_indices->element[k]) {
                        if (s==0){
                                l_shared=PO1->edge_indices->element[l];
                                *l_po1=l;
                                *l_po2=k;
                                s=1;
                        }else {
                                printf ("Warning:: polygons %ld and %ld share more than one edge (%ld,%ld)!! \n",PO1->index,PO2->index,PO1->edge_indices->element[l],l_shared);
                                l_shared=no_intersection;
                        }

                }
        }
}

distance=distance2D(PO1->centroid,PO2->centroid);
*dist_centroids=distance;
//printf("... PO1=%ld PO2=%ld dist=%lf",PO1->index,PO2->index,distance);
//stop_execution();
return l_shared;

}