324 lines
11 KiB
C#
324 lines
11 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Collections.ObjectModel;
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using System.Diagnostics.CodeAnalysis;
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using Microsoft.Xna.Framework;
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using Syntriax.Engine.Core;
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using Syntriax.Engine.Core.Abstract;
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using Syntriax.Engine.Physics2D.Abstract;
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namespace Syntriax.Engine.Physics2D;
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public class Collider2DBehaviour(IList<Vector2> vertices) : BehaviourOverride, ICollider2D
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{
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private List<Triangle> triangles = new List<Triangle>(32);
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private readonly List<Vector2> _vertices = new List<Vector2>(32);
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private IRigidBody2D? _rigidBody2D = null;
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public Action<IAssignableTransform>? OnTransformAssigned { get => GameObject.OnTransformAssigned; set => GameObject.OnTransformAssigned = value; }
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public Action<ICollider2D, ICollider2D>? OnCollision { get; set; } = null;
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private IList<Vector2> verticesOriginal { get; } = vertices;
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public Vector2 OffsetPosition { get; set; } = Vector2.Zero;
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public Vector2 OffsetScale { get; set; } = Vector2.One;
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public float OffsetRotation { get; set; } = 0f;
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ITransform IAssignableTransform.Transform => Transform;
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public IReadOnlyList<Vector2> Vertices => _vertices;
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public IRigidBody2D? RigidBody2D
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{
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get
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{
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if (_rigidBody2D is null)
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BehaviourController.TryGetBehaviour(out _rigidBody2D);
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return _rigidBody2D;
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}
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}
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public bool Assign(ITransform transform) => GameObject.Assign(transform);
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public bool CheckCollision(Vector2 point, ICollider2D otherCollider, out Vector2 normal)
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{
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normal = Vector2.UnitX;
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foreach (var triangle in triangles)
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{
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if (!isInside(point, triangle))
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continue;
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OnCollision?.Invoke(this, otherCollider);
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Edge main = new() { A = otherCollider.Transform.Position, B = point };
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foreach (var edge in GetEdges(triangle))
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{
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if (!DoIntersect(main, edge))
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continue;
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normal = edge.A - edge.B;
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normal.Normalize();
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normal = new Vector2(normal.Y, normal.X);
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break;
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}
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return true;
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}
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return false;
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}
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public void RecalculateVertices()
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{
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triangles.Clear();
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_vertices.Clear();
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foreach (var vertex in verticesOriginal)
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{
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Vector2 scaledPosition = new Vector2(vertex.X * Transform.Scale.X * OffsetScale.X, vertex.Y * Transform.Scale.Y * OffsetScale.Y);
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_vertices.Add(scaledPosition + Transform.Position);
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}
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Triangle superTriangle = GetSuperTriangle(_vertices);
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triangles.Add(superTriangle);
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List<Triangle> badTriangles = new(32);
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List<Edge> polygon = new(32);
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foreach (var vertex in _vertices)
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{
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badTriangles.Clear();
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polygon.Clear();
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foreach (var triangle in triangles)
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{
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Circle circle = GetCircumCircle(triangle);
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if (Vector2.DistanceSquared(circle.Center, vertex) <= circle.Radius * circle.Radius)
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badTriangles.Add(triangle);
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}
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foreach (var triangle in badTriangles)
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foreach (var edge in GetEdges(triangle))
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{
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if (DoesEdgeExistInTriangles(edge, badTriangles))
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polygon.Add(edge);
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}
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foreach (var triangle in badTriangles)
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triangles.Remove(triangle);
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foreach (var edge in polygon)
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{
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triangles.Add(new()
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{
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A = edge.A,
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B = edge.B,
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C = vertex
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});
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}
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}
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for (int i = triangles.Count - 1; i >= 0; i--)
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{
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Triangle triangle = triangles[i];
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if (
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triangle.A == superTriangle.A || triangle.A == superTriangle.B || triangle.A == superTriangle.C ||
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triangle.B == superTriangle.A || triangle.B == superTriangle.B || triangle.B == superTriangle.C ||
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triangle.C == superTriangle.A || triangle.C == superTriangle.B || triangle.C == superTriangle.C
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)
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triangles.RemoveAt(i);
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}
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// for (int i = 0; i < triangles.Count; i++)
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// {
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// Triangle triangle = triangles[i];
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// triangle.A += Transform.Position;
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// triangle.B += Transform.Position;
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// triangle.C += Transform.Position;
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// triangles[i] = triangle;
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// }
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}
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private bool DoesEdgeExistInTriangles(Edge edge, List<Triangle> triangles)
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{
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foreach (var triangle in triangles)
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foreach (var edgeOther in GetEdges(triangle))
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if (edge.A == edgeOther.A && edge.B == edgeOther.B)
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return true;
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else if (edge.A == edgeOther.B && edge.B == edgeOther.A)
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return true;
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return false;
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}
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private List<Edge> GetEdges(Triangle triangle)
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=> [
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new() { A = triangle.A, B = triangle.B },
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new() { A = triangle.B, B = triangle.C },
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new() { A = triangle.C, B = triangle.A }
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];
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private Triangle GetSuperTriangle(IReadOnlyList<Vector2> vertices)
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{
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float minX = float.MaxValue, minY = float.MaxValue;
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float maxX = float.MinValue, maxY = float.MinValue;
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foreach (Vector2 point in vertices)
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{
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minX = Math.Min(minX, point.X);
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minY = Math.Min(minY, point.Y);
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maxX = Math.Max(maxX, point.X);
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maxY = Math.Max(maxY, point.Y);
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}
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float dx = maxX - minX;
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float dy = maxY - minY;
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float deltaMax = Math.Max(dx, dy);
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float midX = (minX + maxX) / 2;
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float midY = (minY + maxY) / 2;
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Vector2 p1 = new Vector2(midX - 20 * deltaMax, midY - deltaMax);
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Vector2 p2 = new Vector2(midX, midY + 20 * deltaMax);
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Vector2 p3 = new Vector2(midX + 20 * deltaMax, midY - deltaMax);
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return new Triangle() { A = p1, B = p2, C = p3 };
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}
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private struct Triangle { public Vector2 A, B, C; }
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private double GetArea(Triangle triangle)
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{
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return Math.Abs((triangle.A.X * (triangle.B.Y - triangle.C.Y) +
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triangle.B.X * (triangle.C.Y - triangle.A.Y) +
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triangle.C.X * (triangle.A.Y - triangle.B.Y)) / 2.0);
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}
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/* A function to check whether point P(x, y) lies
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inside the triangle formed by A(x1, y1),
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B(x2, y2) and C(x3, y3) */
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private bool isInside(Vector2 point, Triangle triangle)
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{
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double A = GetArea(triangle);
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/* Calculate area of triangle ABC */
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// double A = area(x1, y1, x2, y2, x3, y3);
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double A1 = GetArea(new() { A = point, B = triangle.B, C = triangle.C });
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/* Calculate area of triangle PBC */
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// double A1 = area(x, y, x2, y2, x3, y3);
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/* Calculate area of triangle PAC */
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double A2 = GetArea(new() { A = triangle.A, B = point, C = triangle.C });
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// double A2 = area(x1, y1, x, y, x3, y3);
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/* Calculate area of triangle PAB */
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double A3 = GetArea(new() { A = triangle.A, B = triangle.B, C = point });
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// double A3 = area(x1, y1, x2, y2, x, y);
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/* Check if sum of A1, A2 and A3 is same as A */
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return A == A1 + A2 + A3;
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}
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private struct Edge
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{
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public Vector2 A;
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public Vector2 B;
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}
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private struct Circle
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{
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public double Radius;
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public Vector2 Center;
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}
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private Circle GetCircumCircle(Triangle triangle)
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{
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Circle result = new();
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Vector2 midAB = (triangle.A + triangle.B) / 2;
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Vector2 midBC = (triangle.B + triangle.C) / 2;
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float slopeAB = (triangle.B.Y - triangle.A.Y) / (triangle.B.X - triangle.A.X);
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float slopeBC = (triangle.C.Y - triangle.B.Y) / (triangle.C.X - triangle.B.X);
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// Check if the slopes are not parallel
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if (Math.Abs(slopeAB - slopeBC) > float.Epsilon)
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{
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float x = (slopeAB * slopeBC * (triangle.A.Y - triangle.C.Y) + slopeBC * (triangle.A.X + triangle.B.X) - slopeAB * (triangle.B.X + triangle.C.X)) / (2 * (slopeBC - slopeAB));
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float y = -(x - (triangle.A.X + triangle.B.X) / 2) / slopeAB + (triangle.A.Y + triangle.B.Y) / 2;
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result.Center = new Vector2(x, y);
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result.Radius = Vector2.Distance(result.Center, triangle.A);
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}
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else
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{
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// If slopes are parallel, use the midpoints of the sides as the circumcenter
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result.Center = (midAB + midBC) / 2;
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result.Radius = Vector2.Distance(result.Center, triangle.A);
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}
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return result;
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}
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// Given three collinear points p, q, r, the function checks if
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// point q lies on line segment 'pr'
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private bool OnSegment(Vector2 p, Vector2 q, Vector2 r)
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{
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if (q.X <= Math.Max(p.X, r.X) && q.X >= Math.Min(p.X, r.X) &&
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q.Y <= Math.Max(p.Y, r.Y) && q.Y >= Math.Min(p.Y, r.Y))
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return true;
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return false;
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}
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// To find orientation of ordered triplet (p, q, r).
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// The function returns following values
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// 0 --> p, q and r are collinear
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// 1 --> Clockwise
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// 2 --> Counterclockwise
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private int Orientation(Vector2 p, Vector2 q, Vector2 r)
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{
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// See https://www.geeksforgeeks.org/orientation-3-ordered-points/
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// for details of below formula.
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float val = (q.Y - p.Y) * (r.X - q.X) -
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(q.X - p.X) * (r.Y - q.Y);
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if (val == 0) return 0; // collinear
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return (val > 0) ? 1 : 2; // clock or counterclock wise
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}
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// The main function that returns true if line segment 'edge1.Aedge1.B'
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// and 'edge2.Aedge2.B' intersect.
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private bool DoIntersect(Edge edge1, Edge edge2)
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{
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// Find the four orientations needed for general and
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// special cases
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int o1 = Orientation(edge1.A, edge1.B, edge2.A);
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int o2 = Orientation(edge1.A, edge1.B, edge2.B);
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int o3 = Orientation(edge2.A, edge2.B, edge1.A);
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int o4 = Orientation(edge2.A, edge2.B, edge1.B);
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// General case
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if (o1 != o2 && o3 != o4)
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return true;
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// Special Cases
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// edge1.A, edge1.B and edge2.A are collinear and edge2.A lies on segment edge1.Aedge1.B
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if (o1 == 0 && OnSegment(edge1.A, edge2.A, edge1.B)) return true;
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// edge1.A, edge1.B and edge2.B are collinear and edge2.B lies on segment edge1.Aedge1.B
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if (o2 == 0 && OnSegment(edge1.A, edge2.B, edge1.B)) return true;
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// edge2.A, edge2.B and edge1.A are collinear and edge1.A lies on segment edge2.Aedge2.B
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if (o3 == 0 && OnSegment(edge2.A, edge1.A, edge2.B)) return true;
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// edge2.A, edge2.B and edge1.B are collinear and edge1.B lies on segment edge2.Aedge2.B
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if (o4 == 0 && OnSegment(edge2.A, edge1.B, edge2.B)) return true;
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return false; // Doesn't fall in any of the above cases
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}
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}
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