MoonTools.Bonk/Bonk/Shapes/Polygon.cs

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using System;
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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.Structs;
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namespace MoonTools.Bonk
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{
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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 be defined in clockwise order, have more than 2 vertices, be convex, and have no duplicate vertices.
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/// </summary>
public struct Polygon : IShape2D, IEquatable<Polygon>
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{
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public ImmutableArray<Position2D> Vertices { get; private set; }
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public AABB AABB { get; }
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public int VertexCount { get { return Vertices.Length; } }
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// vertices are local to the origin
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public Polygon(IEnumerable<Position2D> vertices)
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{
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Vertices = vertices.ToImmutableArray();
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AABB = AABB.FromVertices(vertices);
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}
public Polygon(ImmutableArray<Position2D> vertices)
{
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Vertices = vertices;
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AABB = AABB.FromVertices(vertices);
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}
public Vector2 Support(Vector2 direction, Transform2D transform)
{
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var maxDotProduct = float.NegativeInfinity;
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var maxVertex = Vertices[0].ToVector2();
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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;
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}
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public AABB TransformedAABB(Transform2D transform)
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{
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return AABB.Transformed(AABB, transform);
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}
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public override bool Equals(object obj)
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{
return obj is IShape2D other && Equals(other);
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}
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public bool Equals(IShape2D other)
{
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return other is Polygon otherPolygon && Equals(otherPolygon);
}
public bool Equals(Polygon other)
{
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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; }
}
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return true;
}
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public override int GetHashCode()
{
return HashCode.Combine(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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}
}