/// <summary>
/// Checks to see if two polygons intersect
/// </summary>
/// <param name="a">The first polygon.</param>
/// <param name="b">The second polygon.</param>
/// <returns>True if the two polygons intersect. False otherwise.</returns>
public static bool Intersects(IPolygon2D a, IPolygon2D b)
{
// See if this polygon's points are contained in the other polygon
for (int i = 0; i < a.NumSides; i++)
{
if (b.Contains(a.Vertices[i]))
{
return(true);
}
}
// See if this polygon contains the other polygon's points
for (int i = 0; i < b.NumSides; i++)
{
if (a.Contains(b.Vertices[i]))
{
return(true);
}
}
// See if any of the polygon edges intersect each other
for (int i = 0; i < a.NumSides; i++)
{
Vector2 edgeStart = a.Vertices[i];
Vector2 edgeEnd = (i == a.NumSides - 1 ? a.Vertices[0] : a.Vertices[i + 1]);
for (int j = 0; j < b.NumSides; j++)
{
Vector2 otherEdgeStart = a.Vertices[j];
Vector2 otherEdgeEnd = (j == a.NumSides - 1 ? a.Vertices[0] : a.Vertices[j + 1]);
if (ShapeUtility.AreEdgesIntersecting(edgeStart, edgeEnd, otherEdgeStart, otherEdgeEnd))
{
return(true);
}
}
}
return(false);
}
/// <summary>
/// Checks for intersection between a polygon and a circle.
/// </summary>
/// <param name="polygon">The circle.</param>
/// <param name="circle">The polygon.</param>
/// <returns>True if the two shapes intersect. False othwerise.</returns>
public static bool Intersects(IPolygon2D polygon, ICircle2D circle)
{
// See if the closest point of each edge to the circle's center is inside the center
Vector2 circleCenter = circle.Center;
for (int i = 0; i < polygon.NumSides; i++)
{
Vector2 closestPointOfEdge =
(i == polygon.NumSides - 1 ?
ShapeUtility.CalculateClosestPointOnEdge(circleCenter, polygon.Vertices[i], polygon.Vertices[0]) :
ShapeUtility.CalculateClosestPointOnEdge(circleCenter, polygon.Vertices[i], polygon.Vertices[i + 1]));
if (circle.Contains(closestPointOfEdge))
{
return(true);
}
}
// See if this polygon contains the other circle
if (polygon.Contains(circle.Center))
{
return(true);
}
return(false);
}