Unity UGUI 程序化网格 08：内外半径生成环形技能范围

// Assets/OnPopulateMeshBook/Chapters/Chapter08_Ring/
// Runtime/RingGraphic.cs · 字段、属性与生成入口
using UnityEngine;
using UnityEngine.UI;

namespace OnPopulateMeshBook.Chapter08
{
    public sealed class RingGraphic : Graphic
    {
        [SerializeField, Min(0f)] private float innerRadius = 70f;
        [SerializeField, Min(0f)] private float outerRadius = 90f;
        [SerializeField, Min(3)] private int segments = 24;

        public float InnerRadius
        {
            get => innerRadius;
            set { innerRadius = Mathf.Max(0f, value); SetVerticesDirty(); }
        }

        public float OuterRadius
        {
            get => outerRadius;
            set { outerRadius = Mathf.Max(0f, value); SetVerticesDirty(); }
        }

        public int Segments
        {
            get => segments;
            set { segments = Mathf.Max(3, value); SetVerticesDirty(); }
        }

        protected override void OnPopulateMesh(VertexHelper vh)
        {
            vh.Clear();
            var inner = Mathf.Clamp(innerRadius, 0f, outerRadius);
            if (outerRadius <= 0f || inner >= outerRadius) return;
            var segmentCount = Mathf.Max(3, segments);

            if (inner <= 0f)
            {
                AddVertex(vh, Vector2.zero);
                for (var i = 0; i < segmentCount; i++)
                {
                    var radians = i * Mathf.PI * 2f / segmentCount;
                    AddVertex(vh, new Vector2(
                        Mathf.Cos(radians), Mathf.Sin(radians)) * outerRadius);
                }
                for (var i = 0; i < segmentCount; i++)
                    vh.AddTriangle(0, i + 1,
                        (i + 1) % segmentCount + 1);
                return;
            }

            for (var i = 0; i <= segmentCount; i++)
            {
                var radians = i * Mathf.PI * 2f / segmentCount;
                var direction = new Vector2(
                    Mathf.Cos(radians), Mathf.Sin(radians));
                AddVertex(vh, direction * inner);
                AddVertex(vh, direction * outerRadius);
            }

            for (var i = 0; i < segmentCount; i++)
            {
                var start = i * 2;
                vh.AddTriangle(start, start + 1, start + 3);
                vh.AddTriangle(start + 3, start + 2, start);
            }
        }

        private void AddVertex(VertexHelper vh, Vector2 position)
        {
            var vertex = UIVertex.simpleVert;
            vertex.position = position;
            vertex.color = color;
            vh.AddVert(vertex);
        }
    }
}

{
  "fixedInput": "inner=70 outer=125 segments=8",
  "component": "RingGraphic",
  "vertexCount": 18,
  "indexCount": 48,
  "samples": [
    { "i": 0, "inner": [70.0,0.0], "outer": [125.0,0.0] },
    { "i": 1, "inner": [49.497475,49.497475],
              "outer": [88.388344,88.388344] },
    { "i": 2, "inner": [-0.000003,70.0],
              "outer": [-0.000005,125.0] },
    { "i": 8, "inner": [70.0,0.000012],
              "outer": [125.0,0.000022] }
  ],
  "firstIndices": [0,1,3, 3,2,0],
  "lastIndices": [14,15,17, 17,16,14]
}

N = 8
sampleGroups = N + 1 = 9
verticesPerGroup = 2
vertexCount = 2(N+1) = 18

quads = N = 8
trianglesPerQuad = 2
indexCount = N * 2 * 3 = 48

group i:
inner=i*2, outer=i*2+1
nextInner=i*2+2, nextOuter=i*2+3

// Assets/OnPopulateMeshBook/Chapters/Chapter08_Ring/
// Tests/Editor/RingGraphicTests.cs
[Test]
public void Populate_EightSegmentsHaveClosedBandCounts()
{
    var graphic = MeshTestSupport.CreateGraphic<RingGraphic>(
        new Vector2(220f, 220f));
    graphic.InnerRadius = 60f;
    graphic.OuterRadius = 100f;
    graphic.Segments = 8;
    var mesh = MeshTestSupport.Build(graphic);

    Assert.That(mesh.vertexCount, Is.EqualTo(18));
    Assert.That(mesh.triangles, Has.Length.EqualTo(48));
    Assert.That(Vector3.Distance(
        mesh.vertices[0], mesh.vertices[16]), Is.LessThan(0.001f));
    Assert.That(Vector3.Distance(
        mesh.vertices[1], mesh.vertices[17]), Is.LessThan(0.001f));
    MeshTestSupport.AssertIndicesInRange(mesh);
    MeshTestSupport.Destroy(graphic, mesh);
}

[Test]
public void Populate_InvertedRadiiProduceEmptyMesh()
{
    var graphic = MeshTestSupport.CreateGraphic<RingGraphic>(
        new Vector2(220f, 220f));
    graphic.InnerRadius = 100f;
    graphic.OuterRadius = 60f;
    var mesh = MeshTestSupport.Build(graphic);

    Assert.That(mesh.vertexCount, Is.Zero);
    MeshTestSupport.Destroy(graphic, mesh);
}

[Test]
public void Populate_ZeroInnerRadiusUsesTriangleFan()
{
    var graphic = MeshTestSupport.CreateGraphic<RingGraphic>(
        new Vector2(220f, 220f));
    graphic.InnerRadius = 0f;
    graphic.OuterRadius = 100f;
    graphic.Segments = 8;
    var mesh = MeshTestSupport.Build(graphic);

    Assert.That(mesh.vertexCount, Is.EqualTo(9));
    Assert.That(mesh.triangles, Has.Length.EqualTo(24));
    MeshTestSupport.AssertFinite(mesh);
    MeshTestSupport.AssertIndicesInRange(mesh);
    MeshTestSupport.Destroy(graphic, mesh);
}

"$UNITY_EDITOR" \
  -batchmode -nographics \
  -projectPath "$PROJECT_ROOT/.tmp/unity-onpopulate-mesh-lab" \
  -runTests -testPlatform EditMode \
  -testResults "$ARTIFACTS/editmode-results.xml" \
  -logFile "$ARTIFACTS/editmode.log"

process_exit_code=0
total=19 passed=19 failed=0 skipped=0
duration=0.0400379s

Populate_EightSegmentsHaveClosedBandCounts
result=Passed duration=0.002224s
vertexCount=18 indexCount=48
innerClosureDistance<0.001
outerClosureDistance<0.001

Populate_InvertedRadiiProduceEmptyMesh
result=Passed duration=0.000107s vertexCount=0

Populate_ZeroInnerRadiusUsesTriangleFan
result=Passed duration=0.000119s
vertexCount=9 indexCount=24 finite=true indicesInRange=true

Populate_SegmentCountClampsToThree
result=Passed duration=0.000132s

// 错误：缺少闭合的第 N 组
for (var i = 0; i < segments; i++)
{
    var radians = i * Mathf.PI * 2f / segments;
    var direction = new Vector2(
        Mathf.Cos(radians), Mathf.Sin(radians));
    AddVertex(vh, direction * inner);
    AddVertex(vh, direction * outerRadius);
}

// N=8 只产生 16 顶点，最后一段公式需要编号 16、17。
// 修复：顶点循环使用 i <= segments。