Question

Suppose you have have a rectangle, bottom-left point 0,0 and upper-right point is 100,100.
Now two line intersects the rectangle. I have to find out the coordinate of the intersection point. I have done that. Now the problem is I can’t tell whether it is inside the rectangle or not. I used double comparison. But I think it is giving me wrong answer. Suppose the intersection point is ( x , y ). I used this checking for comparison : if( x >= 0.0 && x <= 100.0 && y >= 0.0 && y <= 100.0 ). What should I do?

//this function generates line
line genline( int x1 , int y1 , int x2 , int y2 ){
    line l ;
    l.A = y2 - y1 ;
    l.B = x1 - x2 ;
    l.C = l.A * x1 + l.B * y1 ;
    return l ;
}
//this function checks intersection
bool intersect( line m ,line n ) {
    int det = m.A * n.B - m.B * n.A ;
    if( det == 0 ){
        return false ;
    }
    else {
        double x = ( n.B * m.C - m.B * n.C ) / ( det * 1.0 ) ;
        double y = ( m.A * n.C - n.A * m.C ) / ( det * 1.0 ) ;        
        if( x >= 0.0 && x <= L && y >= 0.0 && y <= W ) { return true ; }
        else{ return false ; }
    }
}

EDIT:
Both the line are stretched to infinity.

Answer 1

Your math looks like it’s right. By the way, If a line intersects something, it is always inside that something.