MoonTools.Bonk/Bonk/Shapes/Polygon.cs

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using System.Linq;
using System;
using System.Collections.Generic;
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using System.Collections.Immutable;
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using System.Numerics;
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using MoonTools.Core.Structs;
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using MoreLinq;
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namespace MoonTools.Core.Bonk
{
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/// <summary>
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/// A Shape defined by an arbitrary collection of vertices.
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/// NOTE: A Polygon must have more than 2 vertices, be convex, and should not have duplicate vertices.
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/// </summary>
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public struct Polygon : IShape2D, IEquatable<IShape2D>
{
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private ImmutableArray<Position2D> vertices;
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public IEnumerable<Position2D> Vertices { get { return vertices == null ? Enumerable.Empty<Position2D>() : vertices; } }
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// vertices are local to the origin
public Polygon(params Position2D[] vertices)
{
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this.vertices = ImmutableArray.Create<Position2D>(vertices);
}
public Polygon(ImmutableArray<Position2D> vertices)
{
this.vertices = vertices;
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}
public Vector2 Support(Vector2 direction, Transform2D transform)
{
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return Vertices.Select(vertex => Vector2.Transform(vertex, transform.TransformMatrix)).MaxBy(transformed => Vector2.Dot(transformed, direction)).First();
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}
public AABB AABB(Transform2D Transform2D)
{
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return Bonk.AABB.FromTransformedVertices(Vertices, Transform2D);
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}
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public override bool Equals(object obj)
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{
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if (obj is IShape2D other)
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{
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return Equals(other);
}
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return false;
}
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public bool Equals(IShape2D other)
{
if (other is Polygon otherPolygon)
{
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var q = from a in vertices
join b in otherPolygon.vertices on a equals b
select a;
return vertices.Length == otherPolygon.vertices.Length && q.Count() == vertices.Length;
}
else if (other is Rectangle rectangle)
{
var q = from a in vertices
join b in rectangle.Vertices on a equals b
select a;
return vertices.Length == 4 && q.Count() == vertices.Length;
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}
return false;
}
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public override int GetHashCode()
{
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return HashCode.Combine(vertices, Vertices);
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}
public static bool operator ==(Polygon a, Polygon b)
{
return a.Equals(b);
}
public static bool operator !=(Polygon a, Polygon b)
{
return !(a == b);
}
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public static bool operator ==(Polygon a, Rectangle b)
{
return a.Equals(b);
}
public static bool operator !=(Polygon a, Rectangle b)
{
return !(a == b);
}
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}
}