从文件导入的自定义地球国家网格渲染不完整问题排查

你的问题出在三角扇的三角化逻辑完全不适合国家轮廓这类复杂球面多边形。

原代码里，你把第一个顶点作为扇心，依次连接i和i+1顶点构建三角扇，但国家的边界顶点是按地理轮廓顺序排列的，并非围绕某个中心点的放射状序列——这种方式仅适用于简单的平面凸多边形，完全无法适配球面凹多边形、跨经度的复杂轮廓，自然会出现部分区域渲染缺失的情况。

解决步骤 #

1. 替换三角化方式，使用通用多边形三角化工具 #

Unity没有内置复杂多边形三角化API，你可以用一个通用的Triangulator类处理顶点序列的三角化（先将3D球面顶点投影到2D平面完成三角化，再映射回3D球面）。以下是具体实现：

首先添加Triangulator类：

public class Triangulator
{
    private List<Vector2> m_points = new List<Vector2>();

    public Triangulator(Vector2[] points)
    {
        m_points = new List<Vector2>(points);
    }

    public int[] Triangulate()
    {
        List<int> indices = new List<int>();

        int n = m_points.Count;
        if (n < 3)
            return indices.ToArray();

        int[] V = new int[n];
        if (Area() > 0)
        {
            for (int v = 0; v < n; v++)
                V[v] = v;
        }
        else
        {
            for (int v = 0; v < n; v++)
                V[v] = (n - 1) - v;
        }

        int nv = n;
        int count = 2 * nv;
        for (int m = 0, v = nv - 1; nv > 2;)
        {
            if ((count--) <= 0)
                return indices.ToArray();

            int u = v;
            if (nv <= u)
                u = 0;
            v = u + 1;
            if (nv <= v)
                v = 0;
            int w = v + 1;
            if (nv <= w)
                w = 0;

            if (Snip(u, v, w, nv, V))
            {
                int a, b, c, s, t;
                a = V[u];
                b = V[v];
                c = V[w];
                indices.Add(a);
                indices.Add(b);
                indices.Add(c);
                m++;
                for (s = v, t = v + 1; t < nv; s++, t++)
                    V[s] = V[t];
                nv--;
                count = 2 * nv;
            }
        }

        indices.Reverse();
        return indices.ToArray();
    }

    private float Area()
    {
        int n = m_points.Count;
        float A = 0.0f;
        for (int p = n - 1, q = 0; q < n; p = q++)
        {
            Vector2 pval = m_points[p];
            Vector2 qval = m_points[q];
            A += pval.x * qval.y - qval.x * pval.y;
        }
        return A * 0.5f;
    }

    private bool Snip(int u, int v, int w, int n, int[] V)
    {
        int p;
        Vector2 A = m_points[V[u]];
        Vector2 B = m_points[V[v]];
        Vector2 C = m_points[V[w]];
        if (Mathf.Epsilon > (((B.x - A.x) * (C.y - A.y)) - ((B.y - A.y) * (C.x - A.x))))
            return false;
        for (p = 0; p < n; p++)
        {
            if ((p == u) || (p == v) || (p == w))
                continue;
            Vector2 P = m_points[V[p]];
            if (InsideTriangle(A, B, C, P))
                return false;
        }
        return true;
    }

    private bool InsideTriangle(Vector2 A, Vector2 B, Vector2 C, Vector2 P)
    {
        float ax, ay, bx, by, cx, cy, apx, apy, bpx, bpy, cpx, cpy;
        float cCROSSap, bCROSScp, aCROSSbp;

        ax = C.x - B.x; ay = C.y - B.y;
        bx = A.x - C.x; by = A.y - C.y;
        cx = B.x - A.x; cy = B.y - A.y;
        apx = P.x - A.x; apy = P.y - A.y;
        bpx = P.x - B.x; bpy = P.y - B.y;
        cpx = P.x - C.x; cpy = P.y - C.y;

        aCROSSbp = ax * bpy - ay * bpx;
        cCROSSap = cx * apy - cy * apx;
        bCROSScp = bx * cpy - by * cpx;

        return ((aCROSSbp >= 0.0f) && (bCROSScp >= 0.0f) && (cCROSSap >= 0.0f));
    }
}

然后修改你的drawCountry方法：

public void drawCountry()
{
    MeshFilter meshFilter = gameObject.AddComponent<MeshFilter>();
    MeshRenderer meshRenderer = gameObject.AddComponent<MeshRenderer>();
    Mesh mesh = new Mesh();

    // 将3D球面顶点投影到2D平面（赤道附近国家用x-z投影，极地国家建议改用经纬度转2D坐标）
    Vector2[] planeVertices = new Vector2[geoVertices.Length];
    for (int i = 0; i < geoVertices.Length; i++)
    {
        planeVertices[i] = new Vector2(geoVertices[i].x, geoVertices[i].z);
    }

    // 生成正确的三角索引
    Triangulator triangulator = new Triangulator(planeVertices);
    int[] triangles = triangulator.Triangulate();

    mesh.vertices = geoVertices;
    mesh.triangles = triangles;

    mesh.RecalculateNormals();
    mesh.RecalculateBounds();

    meshFilter.mesh = mesh;

    Material material = new Material(Shader.Find("Unlit/Color"));
    material.color = new Color(1f, 0.5f, 0f, 0.5f);
    // 关闭背面剔除，避免球面内侧的面被隐藏
    material.SetInt("_Cull", (int)UnityEngine.Rendering.CullMode.Off);

    meshRenderer.material = material;
}

2. 额外注意事项 #

• 顶点顺序：确保geoVertices中的顶点按国家边界的顺时针/逆时针连续排列，不能出现乱序或跳跃。
• 投影适配：如果是南北极附近的国家，替换投影方式为经纬度转2D坐标（比如经度为x，纬度为y），避免投影变形导致三角化错误。
• 材质设置：关闭背面剔除可以避免球面网格因朝向问题被隐藏。

内容的提问来源于stack exchange，提问作者alcor