using System; using System.Collections.Generic; using System.Collections.Immutable; using System.Numerics; using MoonTools.Structs; namespace MoonTools.Bonk { /// /// A Shape defined by an arbitrary collection of vertices. /// NOTE: A Polygon must be defined in clockwise order, have more than 2 vertices, be convex, and have no duplicate vertices. /// public struct Polygon : IShape2D, IEquatable { public ImmutableArray Vertices { get; private set; } public AABB AABB { get; } public int VertexCount { get { return Vertices.Length; } } // vertices are local to the origin public Polygon(IEnumerable vertices) { Vertices = vertices.ToImmutableArray(); AABB = AABB.FromVertices(vertices); } public Polygon(ImmutableArray vertices) { Vertices = vertices; AABB = AABB.FromVertices(vertices); } public Vector2 Support(Vector2 direction, Transform2D transform) { var maxDotProduct = float.NegativeInfinity; var maxVertex = Vertices[0].ToVector2(); foreach (var vertex in Vertices) { var transformed = Vector2.Transform(vertex, transform.TransformMatrix); var dot = Vector2.Dot(transformed, direction); if (dot > maxDotProduct) { maxVertex = transformed; maxDotProduct = dot; } } return maxVertex; } public AABB TransformedAABB(Transform2D transform) { return AABB.Transformed(AABB, transform); } public override bool Equals(object obj) { return obj is IShape2D other && Equals(other); } public bool Equals(IShape2D other) { return (other is Polygon otherPolygon && Equals(otherPolygon)) || (other is Rectangle rectangle && Equals(rectangle)); } public bool Equals(Polygon other) { if (VertexCount != other.VertexCount) { return false; } int? offset = null; for (var i = 0; i < VertexCount; i++) { if (Vertices[0] == other.Vertices[i]) { offset = i; break; } } if (!offset.HasValue) { return false; } for (var i = 0; i < VertexCount; i++) { if (Vertices[i] != other.Vertices[(i + offset.Value) % VertexCount]) { return false; } } return true; } public bool Equals(Rectangle rectangle) { return RectanglePolygonComparison.Equals(this, rectangle); } public override int GetHashCode() { return HashCode.Combine(Vertices); } public static bool operator ==(Polygon a, Polygon b) { return a.Equals(b); } public static bool operator !=(Polygon a, Polygon b) { return !(a == b); } public static bool operator ==(Polygon a, Rectangle b) { return a.Equals(b); } public static bool operator !=(Polygon a, Rectangle b) { return !(a == b); } } }