/// <summary>
/// non-overlapping Convex polygons can have continuous common edges.
///
/// </summary>
/// <param name="poly1">must be full close loop polygon</param>
/// <param name="poly2">must be full close loop polygon</param>
/// <returns></returns>
static List <mPoint> mergeTwoConvexPolygons(List <mPoint> poly1, List <mPoint> poly2)
{
List <mPoint> ret = new List <mPoint>();
bool found = false;
for (int i = 0; i < poly1.Count - 1; i++)
{
LineSegment l1 = new LineSegment(poly1[i].x, poly1[i].y, poly1[i + 1].x, poly1[i + 1].y);
for (int j = 0; j < poly2.Count - 1; j++)
{
LineSegment l2 = new LineSegment(poly2[j].x, poly2[j].y, poly2[j + 1].x, poly2[j + 1].y);
bool sameDirection = true;
bool sameSegment = false;
if (l1.x1 == l2.x1 && l1.y1 == l2.y1 && l1.x2 == l2.x2 && l1.y2 == l2.y2)
{
sameSegment = true;
sameDirection = true;
}
if (l1.x1 == l2.x2 && l1.y1 == l2.y2 && l1.x2 == l2.x1 && l1.y2 == l2.y1)
{
sameSegment = true;
sameDirection = false;
}
if (sameSegment)
{
// add half chain of poly1, excluding i
for (int p = 0; p < i; p++)
{
ret.Add(poly1[p]);
}
// add the entire poly2, starting from j or j+1 depending on direction
for (int q = 0; q < poly2.Count - 1; q++)
{
if (!sameDirection)
{
int idx = (q + j + 1) % (poly2.Count - 1);
ret.Add(poly2[idx]);
}
else
{
int idx = (j - q + poly2.Count - 1) % (poly2.Count - 1);
ret.Add(poly2[idx]);
}
}
// the other half poly1, excluding i+1
for (int p = i + 2; p < poly1.Count; p++)
{
ret.Add(poly1[p]);
}
found = true; break;
}
}
if (found)
{
break;
}
}
return(ret);
}