【Unity】动态生成圆环体Mesh

代码由ChatGPT生成，后经人工调整。

/// <summary>
/// 创建一个3维圆环体Mesh。
/// </summary>
/// <param name="outerRadius">外半径。</param>
/// <param name="innerRadius">内半径。</param>
/// <param name="numSegments">圆环体段数。值越大，圆环体越圆润。</param>
/// <param name="numSides">圆环体截面边数。值越大，圆环体截面越圆润。</param>
/// <returns></returns>
public static Mesh CreateTorus3DMesh(float outerRadius, float innerRadius, int numSegments = 32, int numSides = 16)
{
    
    
    Mesh mesh = new Mesh();
    mesh.name = "Torus";

    Vector3[] vertices = new Vector3[(numSegments + 1) * (numSides + 1)];
    Vector3[] normals = new Vector3[(numSegments + 1) * (numSides + 1)];
    Vector2[] uv = new Vector2[(numSegments + 1) * (numSides + 1)];
    int[] triangles = new int[numSegments * numSides * 6];

    float angleStep = 2 * Mathf.PI / numSegments;
    float sideAngleStep = 2 * Mathf.PI / numSides;

    float avgRadius = (outerRadius + innerRadius) / 2; // 平均半径
    float secRadius = (outerRadius - innerRadius) / 2; // 截面半径

    int vertexIndex = 0;
    for (int i = 0; i <= numSegments; i++)
    {
    
    
        float segAngle = i * angleStep; // 圆环体分段角

        for (int j = 0; j <= numSides; j++)
        {
    
    
            float sideAngle = j * sideAngleStep; // 圆环体截面角

            // 从right方向开始生成顶点
            Vector3 vertex = new Vector3
            {
    
    
                x = (avgRadius + secRadius * Mathf.Cos(sideAngle)) * Mathf.Cos(segAngle),
                z = (avgRadius + secRadius * Mathf.Cos(sideAngle)) * Mathf.Sin(segAngle),
                y = secRadius * Mathf.Sin(sideAngle)
            };

            Vector3 secCenter = new Vector3
            {
    
    
                x = avgRadius * Mathf.Cos(segAngle),
                z = avgRadius * Mathf.Sin(segAngle),
                y = 0,
            };

            vertices[vertexIndex] = vertex;
            normals[vertexIndex] = (vertex - secCenter).normalized;
            uv[vertexIndex] = new Vector2((float)i / numSegments, (float)j / numSides);

            vertexIndex++;
        }
    }

    int triangleIndex = 0;
    for (int i = 0; i < numSegments; i++)
    {
    
    
        for (int j = 0; j < numSides; j++)
        {
    
    
            int topLeft = (i + 1) * (numSides + 1) + j;
            int topRight = topLeft + 1;
            int bottomLeft = i * (numSides + 1) + j;
            int bottomRight = bottomLeft + 1;

            triangles[triangleIndex] = topLeft;
            triangles[triangleIndex + 1] = bottomLeft;
            triangles[triangleIndex + 2] = topRight;
            triangles[triangleIndex + 3] = topRight;
            triangles[triangleIndex + 4] = bottomLeft;
            triangles[triangleIndex + 5] = bottomRight;

            triangleIndex += 6;
        }
    }

    mesh.vertices = vertices;
    mesh.triangles = triangles;
    mesh.normals = normals;
    mesh.uv = uv;

    return mesh;
}