public static bool intersection(Line lineA, Line lineB)
{
/* Returns true if segments collide
* If they have in common a segment edge returns false
* Algorithm obtained from:
* http://stackoverflow.com/questions/3838329/how-can-i-check-if-two-segments-intersect
* Thanks OMG_peanuts !
* */
double dif;
double A1, A2;
double b1, b2;
decimal X;
if (Math.Max(lineA.nodes[0].x, lineA.nodes[1].x) < Math.Min(lineB.nodes[0].x, lineB.nodes[1].x))
{
return(false); //Not a chance of intersection
}
dif = lineA.nodes[0].x - lineA.nodes[1].x;
if (dif != 0) //Avoids dividing by 0
{
A1 = (lineA.nodes[0].y - lineA.nodes[1].y) / dif;
}
else
{
//Segment is vertical
A1 = 9999999;
}
dif = lineB.nodes[0].x - lineB.nodes[1].x;
if (dif != 0) //Avoids dividing by 0
{
A2 = (lineB.nodes[0].y - lineB.nodes[1].y) / dif;
}
else
{
//Segment is vertical
A2 = 9999999;
}
if (A1 == A2)
{
return(false); //Parallel
}
else if (A1 == 9999999)
{
return(verticalIntersection(lineA, lineB));
}
else if (A2 == 9999999)
{
return(verticalIntersection(lineB, lineA));
}
b1 = lineA.nodes[0].y - (A1 * lineA.nodes[0].x);
b2 = lineB.nodes[0].y - (A2 * lineB.nodes[0].x);
X = Math.Round(System.Convert.ToDecimal((b2 - b1) / (A1 - A2)), 4);
if ((X <= System.Convert.ToDecimal(Math.Max(Math.Min(lineA.nodes[0].x, lineA.nodes[1].x), Math.Min(lineB.nodes[0].x, lineB.nodes[1].x)))) ||
(X >= System.Convert.ToDecimal(Math.Min(Math.Max(lineA.nodes[0].x, lineA.nodes[1].x), Math.Max(lineB.nodes[0].x, lineB.nodes[1].x)))))
{
return(false); //Out of bound
}
else
{
return(true);
}
}
public static bool tangentToHull(Line line_treated, Node node, decimal cos1, decimal cos2, List <Line> concave_hull)
{
/* A new middlepoint could (rarely) make a segment that's tangent to the hull.
* This method detects these situations
* I suggest turning this method of if you are not using square grids or if you have a high dot density
* */
bool isTangent = false;
decimal current_cos1;
decimal current_cos2;
double edge_length;
List <int> nodes_searched = new List <int>();
Line line;
Node node_in_hull;
int count_line = 0;
int count_node = 0;
edge_length = Line.getLength(node, line_treated.nodes[0]) + Line.getLength(node, line_treated.nodes[1]);
while (!isTangent && count_line < concave_hull.Count)
{
line = concave_hull[count_line];
while (!isTangent && count_node < 2)
{
node_in_hull = line.nodes[count_node];
if (!nodes_searched.Contains(node_in_hull.id))
{
if (node_in_hull.id != line_treated.nodes[0].id && node_in_hull.id != line_treated.nodes[1].id)
{
current_cos1 = getCos(node_in_hull, line_treated.nodes[0], line_treated.nodes[1]);
current_cos2 = getCos(node_in_hull, line_treated.nodes[1], line_treated.nodes[0]);
if (current_cos1 == cos1 || current_cos2 == cos2)
{
isTangent = (Line.getLength(node_in_hull, line_treated.nodes[0]) + Line.getLength(node_in_hull, line_treated.nodes[1]) < edge_length);
}
}
}
nodes_searched.Add(node_in_hull.id);
count_node++;
}
count_node = 0;
count_line++;
}
return(isTangent);
}