Question

我很擅长使用linq。我的目标是列表的元素（vector3s）具有属性x和z，并且想要找到x或z值相同的2个vector3元素的平均值。例如，如果你有一个地板，它有4个顶点a，b，c，d，其中a是topleft角，b是顶角，c是左下角，d是右下角。我想找到ab，cd，bd，ac之间的中间点。我实际上有一个字典，其中一个游戏对象楼层在vector3列表中有相应的顶点。到目前为止，这将解释我的代码。

Dictionary<GameObject, List<Vector3>> floorVertices = new Dictionary<GameObject, List<Vector3>>();
List<Vector3> vertices = new List<Vector3>();

verticeMidpoints = (
        from l in floorVertices.Values 
        from v in l 
        where l.Any(v2 => v2.x == v.x || v2.z == v.z) 
        select (new Vector3((v.x + v2.x) / 2), 
                            (v.y + v2.y) / 2, 
                            (v.z + v2.z) / 2);
    ).ToList();

继承代码以找到顶点。

// the floor has 8 vertices and I would like the bottom ones that touch the ground
vertices = (
        from v in vertices 
        where v.y < ((  from v2 in vertices 
                        select v2.y
                      ).Average()) 
        select v
    ).ToList();

我如何调整（无法访问v2的地方）

verticeMidpoints = (
        from l in floorVertices.Values 
        from v in l 
        where l.Any(v2 => v2.x == v.x || v2.z == v.z) 
        select (new Vector3((v.x + v2.x) / 2), 
                            (v.y + v2.y) / 2, 
                            (v.z + v2.z) / 2)
    ).ToList();

让它发挥作用。

我很确定找到顶点的代码有更多代码需要。请帮忙

Answer 1

就像我在评论中所说的那样，精心设计的LINQ查询可以使代码干净简洁，对性能影响很小或没有影响，但除非您对LINQ知识有信心，否则应尽可能避免执行速度为一个主要问题（就像游戏编程一样）。

相反，您应该使用辅助方法和常规循环来获取您之后的内容：

获取顶点：

public List<Vector3> GetFloorVertices(List<Vector3> vertices)
{
    // Preallocate memory for the list so we don't 
    // need to worry about reallocating on insertions
    List<Vector3> floorVerts = new List<Vector3>(vertices.Count);
    float avg = vertices.Average(v => v.y);

    for (int i = 0; i < vertices.Count; i++)
    {
        if (vertices[i].y < avg)
        {
            floorVerts.Add(vertices[i]);
        }
    }

    return floorVerts;
}

获得中点：

public List<Vector3> GetMidpoints(List<Vector3> vertices)
{
    // Preallocate memory for the list so we don't 
    // need to worry about reallocating on insertions
    List<Vector3> midpoints = new List<Vector3>(vertices.Count * vertices.Count);

    for (int i = 0; i < vertices.Count; i++)
    {
        for (int j = 0; j < vertices.Count; j++)
        {
            if (vertices[i].x != vertices[j].x && vertices[i].z != vertices[j].z)
                continue;

            midpoints.Add(new Vector3(
                            (vertices[i].x + vertices[j].x) / 2,
                            (vertices[i].y + vertices[j].y) / 2,
                            (vertices[i].z + vertices[j].z) / 2
            ));
        }
    }

    return midpoints;
}

Answer 2

查看let条款

这样的事情 verticeMidpoints = ( from l in floorVertices.Values from v in l let v2 = ....... ).ToList();

linq如何访问变量

2 个答案: