dpoint centre(Point p1, Point p2, Point p3) {
Point n1,n2;
double c1,c2;
n1=vector(p1,p2);
n2=vector(p2,p3);
c1=calculate_c(n1,midpoint(p1,p2));
c2=calculate_c(n2,midpoint(p2,p3));
return intersect(n1,n2,c1,c2);
}
Point compute_v(CHpoints *P) {
/* B
-------------
| | ^ ^
A | SCREEN | C | | -> ->
| | Bn Dn An Cn
-------------
D */
Point An,Bn,Cn,Dn; /* Normalvectors to the Screen borders A,B,C,D */
Point n; /* Normalvector to the bisector between P and Next(p) */
double c; /* the constant in the equation ax+by=c, where (a,b) is
normalvector to the bisetor */
Point i;
dpoint di;
/* Point where bisector of P and next(P) intersects with border */
Point p,np;
double minX, minY, maxX, maxY; /* Max, min X and Y coordinate */
minX=-10000.0;
minY=-10000.0;
maxX=10000.0;
maxY=10000.0;
An.x=1; An.y=0; /* Setup normalvectores for the border lines */
Bn.x=0; Bn.y=1;
Cn.x=1; Cn.y=0;
Dn.x=0; Dn.y=1;
p=P->node; /* p=P and np=next(P) */
np=next(P)->node;
n=vector(p,np);
c=calculate_c(n,midpoint(p,np));
if ((p.x < np.x) && (p.y < np.y)) { /* intersects either D or A */
di=intersect(n,Dn,c,maxY);
if ((minX>di.x) || (di.x>maxX))
di=intersect(n,An,c,minX);
}
else if ((p.x < np.x) && (p.y == np.y)) { /* intersects D */
di=intersect(n,Dn,c,maxY);
}
else if ((p.x < np.x) && (p.y > np.y)) { /* intersects either D or C */
di=intersect(n,Dn,c,maxY);
if ((minX>di.x) || (di.x>maxX))
di=intersect(n,Cn,c,maxX);
}
else if ((p.x == np.x) && (p.y < np.y)) { /* intersects A */
di=intersect(n,An,c,minX);
}
else if ((p.x == np.x) && (p.y > np.y)) { /* intersects C */
di=intersect(n,Cn,c,maxX);
}
else if ((p.x > np.x) && (p.y < np.y)) { /* intersects either A or B */
di=intersect(n,Bn,c,minY);
if ((minX>di.x) || (di.x>maxX))
di=intersect(n,An,c,minX);
}
else if ((p.x > np.x) && (p.y == np.y)) /* intersects B */
di=intersect(n,Bn,c,minY);
else if ((p.x > np.x) && (p.y > np.y)) { /* intersects either C or B */
di=intersect(n,Bn,c,minY);
if ((minX>di.x) || (di.x>maxX))
di=intersect(n,Cn,c,maxX);
}
else {
printf("Error: Can't intersect\n");
exit(1);
}
i.x= (int)di.x;
i.y= (int)di.y;
return i;
}
