60 lines
2.0 KiB
C#
60 lines
2.0 KiB
C#
using System.Collections.Generic;
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using Unity.Mathematics;
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namespace UnityEngine.U2D.Animation
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{
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internal static class MeshUtilities
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{
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/// <summary>
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/// Get the outline edges from a set of indices.
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/// This method expects the index array to be laid out with one triangle for every 3 indices.
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/// E.g. triangle 0: index 0 - 2, triangle 1: index 3 - 5, etc.
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/// </summary>
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public static int2[] GetOutlineEdges(in int[] indices)
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{
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var edges = new Dictionary<int, int3>(indices.Length / 3);
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for (var i = 0; i < indices.Length; i += 3)
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{
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var i0 = indices[i];
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var i1 = indices[i + 1];
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var i2 = indices[i + 2];
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var edge0 = new int2(i0, i1);
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var edge1 = new int2(i1, i2);
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var edge2 = new int2(i2, i0);
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AddToEdgeMap(edge0, ref edges);
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AddToEdgeMap(edge1, ref edges);
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AddToEdgeMap(edge2, ref edges);
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}
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var outlineEdges = new List<int2>(edges.Count);
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foreach(var edgePair in edges)
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{
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// If an edge is only used in one triangle, it is an outline edge.
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if (edgePair.Value.z == 1)
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outlineEdges.Add(edgePair.Value.xy);
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}
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return outlineEdges.ToArray();
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}
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static void AddToEdgeMap(int2 edge, ref Dictionary<int, int3> edgeMap)
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{
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var tmpEdge = math.min(edge.x, edge.y) == edge.x ? edge.xy : edge.yx;
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var hashCode = tmpEdge.GetHashCode();
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// We store the hashCode as key, so that we can do less GetHashCode-calls.
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// Then we store the count the int3s z-value.
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if (!edgeMap.ContainsKey(hashCode))
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edgeMap.Add(hashCode, new int3(edge, 1));
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else
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{
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var val = edgeMap[hashCode];
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val.z++;
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edgeMap[hashCode] = val;
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}
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}
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}
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} |