86 lines
2.7 KiB
C#
86 lines
2.7 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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using System.Windows.Shapes;
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namespace StructureHelperCommon.Models.Shapes
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{
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public static class PolygonGeometryUtils
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{
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public static ILinePolygonShape GetTransfromedPolygon(ILinePolygonShape polygon, double dx, double dy)
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{
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ILinePolygonShape newPolygon = new LinePolygonShape(Guid.Empty);
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var updateLogic = new LinePolygonShapeUpdateStrategy();
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updateLogic.Update(newPolygon, polygon);
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foreach (var item in newPolygon.Vertices)
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{
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item.Point.X += dx;
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item.Point.Y += dy;
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}
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return newPolygon;
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}
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public static bool DoPolygonsEdgesIntersect(ILinePolygonShape polygon)
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{
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var vertices = polygon.Vertices;
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int n = vertices.Count;
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if (n < 4)
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return false; // Triangles cannot self-intersect
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for (int i = 0; i < n; i++)
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{
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var a1 = vertices[i].Point;
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var a2 = vertices[(i + 1) % n].Point;
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for (int j = i + 1; j < n; j++)
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{
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var b1 = vertices[j].Point;
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var b2 = vertices[(j + 1) % n].Point;
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// Skip adjacent edges (they share a vertex)
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if (AreAdjacent(i, j, n, polygon.IsClosed))
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continue;
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if (SegmentsIntersect(a1, a2, b1, b2))
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return true;
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}
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}
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return false;
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}
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private static bool AreAdjacent(int i, int j, int n, bool isClosed)
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{
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// Edges (i,i+1) and (j,j+1) are adjacent if:
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if (j == i) return true;
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if (j == i + 1) return true;
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if (i == j + 1) return true;
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// Special case: first and last edges in closed polygon
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if (isClosed &&
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((i == 0 && j == n - 1) || (j == 0 && i == n - 1)))
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return true;
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return false;
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}
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private static bool SegmentsIntersect(IPoint2D p1, IPoint2D p2, IPoint2D q1, IPoint2D q2)
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{
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return (Orientation(p1, p2, q1) * Orientation(p1, p2, q2) < 0) &&
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(Orientation(q1, q2, p1) * Orientation(q1, q2, p2) < 0);
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}
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private static int Orientation(IPoint2D a, IPoint2D b, IPoint2D c)
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{
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double val = (b.Y - a.Y) * (c.X - b.X) -
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(b.X - a.X) * (c.Y - b.Y);
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if (Math.Abs(val) < 1e-12) return 0; // Collinear
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return (val > 0) ? 1 : -1; // Clockwise / Counter-clockwise
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}
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}
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}
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