55 lines
1.7 KiB
C#
55 lines
1.7 KiB
C#
using System;
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using Syntriax.Engine.Core;
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namespace Syntriax.Engine.Physics2D.Primitives;
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public record Triangle(Vector2D A, Vector2D B, Vector2D C)
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{
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public float Area => MathF.Abs((
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A.X * (B.Y - C.Y) +
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B.X * (C.Y - A.Y) +
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C.X * (A.Y - B.Y)
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) * .5f);
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public Circle CircumCircle
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{
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get
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{
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Vector2D midAB = (A + B) / 2;
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Vector2D midBC = (B + C) / 2;
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float slopeAB = (B.Y - A.Y) / (B.X - A.X);
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float slopeBC = (C.Y - B.Y) / (C.X - B.X);
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Vector2D center;
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if (MathF.Abs(slopeAB - slopeBC) > float.Epsilon)
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{
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float x = (slopeAB * slopeBC * (A.Y - C.Y) + slopeBC * (A.X + B.X) - slopeAB * (B.X + C.X)) / (2 * (slopeBC - slopeAB));
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float y = -(x - (A.X + B.X) / 2) / slopeAB + (A.Y + B.Y) / 2;
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center = new Vector2D(x, y);
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}
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else
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center = (midAB + midBC) * .5f;
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return new(center, Vector2D.Distance(center, A));
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}
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}
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public bool Overlaps(Vector2D point)
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{
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float originalTriangleArea = Area;
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float pointTriangleArea1 = new Triangle(point, B, C).Area;
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float pointTriangleArea2 = new Triangle(A, point, C).Area;
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float pointTriangleArea3 = new Triangle(A, B, point).Area;
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float pointTriangleAreasSum = pointTriangleArea1 + pointTriangleArea2 + pointTriangleArea3;
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return originalTriangleArea.ApproximatelyEquals(pointTriangleAreasSum, float.Epsilon * 3f);
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}
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public bool ApproximatelyEquals(Triangle other)
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=> A.ApproximatelyEquals(other.A) && B.ApproximatelyEquals(other.B) && C.ApproximatelyEquals(other.C);
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}
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