/// <summary>
/// Determines if the specified polygon at the specified position and rotation contains the specified point
/// </summary>
/// <param name="poly">The polygon</param>
/// <param name="pos">Origin of the polygon</param>
/// <param name="rot">Rotation of the polygon</param>
/// <param name="point">Point to check</param>
/// <param name="strict">True if the edges do not count as inside</param>
/// <returns>If the polygon at pos with rotation rot about its center contains point</returns>
public static bool Contains(Polygon2 poly, Vector2 pos, Rotation2 rot, Vector2 point, bool strict)
{
if (!Rect2.Contains(poly.AABB, pos, point, strict))
{
return(false);
}
// Calculate the area of the triangles constructed by the lines of the polygon. If it
// matches the area of the polygon, we're inside the polygon.
float myArea = 0;
var center = poly.Center + pos;
var last = Math2.Rotate(poly.Vertices[poly.Vertices.Length - 1], poly.Center, rot) + pos;
for (int i = 0; i < poly.Vertices.Length; i++)
{
var curr = Math2.Rotate(poly.Vertices[i], poly.Center, rot) + pos;
myArea += Math2.AreaOfTriangle(center, last, curr);
last = curr;
}
return(Math2.Approximately(myArea, poly.Area, poly.Area / 1000));
}
/// <summary>
/// Initializes a polygon with the specified vertices
/// </summary>
/// <param name="vertices">Vertices</param>
/// <exception cref="ArgumentNullException">If vertices is null</exception>
public Polygon2(Vector2[] vertices)
{
if (vertices == null)
{
throw new ArgumentNullException(nameof(vertices));
}
Vertices = vertices;
Normals = new List <Vector2>();
Vector2 tmp;
for (int i = 1; i < vertices.Length; i++)
{
tmp = Math2.MakeStandardNormal(Vector2.Normalize(Math2.Perpendicular(vertices[i] - vertices[i - 1])));
if (!Normals.Contains(tmp))
{
Normals.Add(tmp);
}
}
tmp = Math2.MakeStandardNormal(Vector2.Normalize(Math2.Perpendicular(vertices[0] - vertices[vertices.Length - 1])));
if (!Normals.Contains(tmp))
{
Normals.Add(tmp);
}
var min = new Vector2(vertices[0].X, vertices[0].Y);
var max = new Vector2(min.X, min.Y);
for (int i = 1; i < vertices.Length; i++)
{
min.X = Math.Min(min.X, vertices[i].X);
min.Y = Math.Min(min.Y, vertices[i].Y);
max.X = Math.Max(max.X, vertices[i].X);
max.Y = Math.Max(max.Y, vertices[i].Y);
}
AABB = new Rect2(min, max);
Center = new Vector2(0, 0);
foreach (var vert in Vertices)
{
Center += vert;
}
Center *= (1.0f / Vertices.Length);
// Find longest axis
float longestAxisLenSq = -1;
for (int i = 1; i < vertices.Length; i++)
{
var vec = vertices[i] - vertices[i - 1];
longestAxisLenSq = Math.Max(longestAxisLenSq, vec.LengthSquared());
}
longestAxisLenSq = Math.Max(longestAxisLenSq, (vertices[0] - vertices[vertices.Length - 1]).LengthSquared());
LongestAxisLength = (float)Math.Sqrt(longestAxisLenSq);
// Area and lines
float area = 0;
Lines = new Line2[Vertices.Length];
var last = Vertices[Vertices.Length - 1];
for (int i = 0; i < Vertices.Length; i++)
{
var next = Vertices[i];
Lines[i] = new Line2(last, next);
area += Math2.AreaOfTriangle(last, next, Center);
last = next;
}
Area = area;
last = Vertices[Vertices.Length - 1];
var centToLast = (last - Center);
var angLast = Math.Atan2(centToLast.Y, centToLast.X);
var cwCounter = 0;
var ccwCounter = 0;
var foundDefinitiveResult = false;
for (int i = 0; i < Vertices.Length; i++)
{
var curr = Vertices[i];
var centToCurr = (curr - Center);
var angCurr = Math.Atan2(centToCurr.Y, centToCurr.X);
var clockwise = angCurr < angLast;
if (clockwise)
{
cwCounter++;
}
else
{
ccwCounter++;
}
Clockwise = clockwise;
if (Math.Abs(angLast - angCurr) > Math2.DEFAULT_EPSILON)
{
foundDefinitiveResult = true;
break;
}
last = curr;
centToLast = centToCurr;
angLast = angCurr;
}
if (!foundDefinitiveResult)
{
Clockwise = cwCounter > ccwCounter;
}
}
