Unity UGUI 程序化网格 07：圆形技能范围的三角扇

// Assets/OnPopulateMeshBook/Chapters/Chapter07_Circle/
// Runtime/CircleGraphic.cs · CircleGraphic
using UnityEngine;
using UnityEngine.UI;

namespace OnPopulateMeshBook.Chapter07
{
    public sealed class CircleGraphic : Graphic
    {
        [SerializeField, Min(0f)] private float radius = 90f;
        [SerializeField, Min(3)] private int segments = 24;

        public float Radius
        {
            get => radius;
            set { radius = 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();
            if (radius <= 0f) return;
            var segmentCount = Mathf.Max(3, segments);

            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)) * radius);
            }

            for (var i = 0; i < segmentCount; i++)
                vh.AddTriangle(0, i + 1,
                    (i + 1) % segmentCount + 1);
        }

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

{
  "fixedInput": "radius=120 segments=8",
  "component": "CircleGraphic",
  "vertexCount": 9,
  "indexCount": 24,
  "vertices": [
    [0.0, 0.0, 0.0],
    [120.0, 0.0, 0.0],
    [84.8528137, 84.8528137, 0.0],
    [-0.0000052, 120.0, 0.0],
    [-84.8528137, 84.8528137, 0.0],
    [-120.0, -0.0000105, 0.0],
    [-84.8527985, -84.8528290, 0.0],
    [0.0000014, -120.0, 0.0],
    [84.8528442, -84.8527832, 0.0]
  ],
  "indices": [
    0,1,2, 0,2,3, 0,3,4, 0,4,5,
    0,5,6, 0,6,7, 0,7,8, 0,8,1
  ]
}

N = 8
angleStep = 2π / 8 = π/4
vertexCount = 1 + N = 9
triangleCount = N = 8
indexCount = 3N = 24

last triangle:
i = 7
current = i + 1 = 8
next = (i + 1) % N + 1 = 1
indices = [0,8,1]

// Assets/OnPopulateMeshBook/Chapters/Chapter07_Circle/
// Tests/Editor/CircleGraphicTests.cs
[Test]
public void Populate_EightSegmentsHaveFixedCounts()
{
    var graphic = MeshTestSupport.CreateGraphic<CircleGraphic>(
        new Vector2(220f, 220f));
    graphic.Radius = 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);
}

[Test]
public void Populate_ZeroRadiusProducesEmptyMesh()
{
    var graphic = MeshTestSupport.CreateGraphic<CircleGraphic>(
        new Vector2(220f, 220f));
    graphic.Radius = 0f;
    var mesh = MeshTestSupport.Build(graphic);

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

[Test]
public void Populate_SegmentCountClampsToThree()
{
    var graphic = MeshTestSupport.CreateGraphic<CircleGraphic>(
        new Vector2(220f, 220f));
    graphic.Radius = 100f;
    graphic.Segments = 1;
    var mesh = MeshTestSupport.Build(graphic);

    Assert.That(graphic.Segments, Is.EqualTo(3));
    Assert.That(mesh.vertexCount, Is.EqualTo(4));
    Assert.That(mesh.triangles, Has.Length.EqualTo(9));
    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"
echo "process_exit_code=$?"

process_exit_code=0
test-run result=Passed
total=19 passed=19 failed=0 skipped=0
duration=0.0400379s

Populate_EightSegmentsHaveFixedCounts
result=Passed duration=0.000671s
vertexCount=9 indexCount=24

Populate_SegmentCountClampsToThree
result=Passed duration=0.000167s
segments=3 vertexCount=4 indexCount=9

Populate_ZeroRadiusProducesEmptyMesh
result=Passed duration=0.000103s
vertexCount=0

// 错误：degrees 被当作 radians
var degrees = i * 360f / segments;
var wrong = new Vector2(
    Mathf.Cos(degrees),
    Mathf.Sin(degrees)) * radius;

// 正确：直接以弧度计算
var radians = i * Mathf.PI * 2f / segments;
var correct = new Vector2(
    Mathf.Cos(radians),
    Mathf.Sin(radians)) * radius;