85 lines
2.8 KiB
C#
85 lines
2.8 KiB
C#
using System.Collections.Generic;
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using UnityEngine;
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namespace VLB
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{
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public class PolygonHelper : MonoBehaviour
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{
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public struct Plane2D
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{
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public Vector2 normal;
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public float distance;
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public float Distance(Vector2 point) { return Vector2.Dot(normal, point) + distance; }
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public Vector2 ClosestPoint(Vector2 pt) { return pt - normal * Distance(pt); }
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public Vector2 Intersect(Vector2 p1, Vector2 p2)
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{
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float denominator = Vector2.Dot(normal, p1 - p2);
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if (Utils.IsAlmostZero(denominator))
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return (p1 + p2) * 0.5f;
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float u = (normal.x * p1.x + normal.y * p1.y + distance) / denominator;
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return (p1 + u * (p2 - p1));
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}
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public bool GetSide(Vector2 point) { return Distance(point) > 0.0f; }
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public static Plane2D FromPoints(Vector3 p1, Vector3 p2)
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{
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var v = (p2 - p1).normalized;
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return new Plane2D
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{
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normal = new Vector2(v.y, -v.x),
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distance = (-v.y * p1.x + v.x * p1.y)
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};
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}
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public static Plane2D FromNormalAndPoint(Vector3 normalizedNormal, Vector3 p1)
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{
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return new Plane2D
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{
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normal = normalizedNormal,
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distance = (-normalizedNormal.x * p1.x - normalizedNormal.y * p1.y)
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};
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}
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public void Flip() { normal = -normal; distance = -distance; }
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public Vector2[] CutConvex(Vector2[] poly)
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{
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Debug.Assert(poly.Length >= 3);
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var polyOut = new List<Vector2>(poly.Length);
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Vector2 startingPoint = poly[poly.Length - 1];
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foreach (var endPoint in poly)
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{
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var startingSide = GetSide(startingPoint);
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var endSide = GetSide(endPoint);
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if (startingSide && endSide)
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{
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polyOut.Add(endPoint);
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}
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else if (startingSide && !endSide)
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{
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polyOut.Add(Intersect(startingPoint, endPoint));
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}
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else if (!startingSide && endSide)
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{
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polyOut.Add(Intersect(startingPoint, endPoint));
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polyOut.Add(endPoint);
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}
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startingPoint = endPoint;
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}
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return polyOut.ToArray();
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}
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public override string ToString() { return string.Format("{0} x {1} + {2}", normal.x, normal.y, distance); }
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}
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}
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}
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