如何从vector 3 1D数组返回y值

I have a vector 3 (x,y,z) 1D dynamic array full of vertex positions.

我有一个向量3(x,y,z)1D动态阵列充满顶点位置。

How would I return the y value at a given x and z coordinate?

如何在给定的x和z坐标处返回y值?

Edit:: Sorry about the lack of detail.

编辑::抱歉缺乏细节。

I am using c++, compiling in Visual Studio 2008. The vector is a vector class storing 3 float values defining an x, y and z variable, it is used for position.

我正在使用c ++,在Visual Studio 2008中进行编译。向量是一个向量类,存储3个定义x,y和z变量的浮点值,它用于位置。

It's like Vector3 *array;

它就像Vector3 *数组;

array = new Vector3[100];

array = new Vector3 [100];

Lots of positional values are added to the array.

大量的位置值被添加到数组中。

When you access a member of the array for a specific value it's like

当您访问数组的成员以获取特定值时,它就像

array[0].y

But I want to find a the y value that corresponds to a specific x and z

但我想找到一个对应于特定x和z的y值

GetY(float x, float z)

GetY(float x,float z)

...

return y;

5 个解决方案

#1

I suppose you have something like

我想你有类似的东西

struct Vec3D{
  float x, y, z;
};

Vec3D vec3d_arr[20];

Then, to get what you want, you'll need to iterate over the array.

然后,为了获得你想要的东西,你需要迭代数组。

float GetYforXZ(Vec3D* arr, unsigned int length, float x_val, float z_val){
  for(unsigned i=0; i < length; ++i){
    if(arr[i].x == x_val && arr[i].z == z_val)
      return arr[i].y;
  }
}

int main(){
  Vec3D arr[20];

  // init arr

  float y = GetYforXZ(arr,20,15.4f,23.3f);
}

Edit: On your comment:

编辑:在你的评论:

#include <map>
#include <math>
using namespace std;

struct Vec3D{
  float x, y, z;
};

const float float_eps = 1e-5;

struct float_wrapper{
    float _value;

    float_wrapper()
        : _value(0.0f) {}

    float_wrapper& operator=(float f){
        _value = f;
        return *this;
    }

    operator float() const{
        return _value;
    }
};

bool operator==(float_wrapper const& lhs, float_wrapper const& rhs){
    float tmp = fabs(lhs._value - rhs._value);
    return tmp < float_eps && tmp >= 0;
}

bool operator<(float_wrapper const& lhs, float_wrapper const& rhs){
    return lhs._value < rhs._value;
}

typedef map< float_wrapper,float_wrapper > zy_map;
typedef map< float_wrapper,zy_map > xzy_map;

void init_vertex_mapping(xzy_map& a_map, Vec3D* arr, size_t length){
  for(size_t i=0; i < length; ++i){
    Vec3D& vertex = arr[i];
    zy_map& zy = a_map[vertex.x];
    zy[vertex.z] = vertex.y;
  }
}

int main(){
  xzy_map vertex_map;
  Vec3D vertex_array[100] = { {0,0,0},{0,0,0},{0,0,0},{-3.14f,42.0f,-13.37f},{0,0,0} };

  init_vertex_mapping(vertex_map, vertex_array, 100);

  float y = vertex_map[-3.14f][-13.37f];
}

Though a problem that I forgot is the inaccuracy of floats, so maybe you get problems with the map. Comment back if you do. :)

虽然我忘记的一个问题是花车的不准确性,所以也许你会遇到地图问题。如果你这样做,请回复。 :)

Edit: Added a more safe version, employing a float_wrapper.

编辑:使用float_wrapper添加了更安全的版本。

#2

You just have to search your array for the vector element with the given x and z coordinates and the get this element's corresponding y value.

您只需要在数组中搜索具有给定x和z坐标的向量元素,并获取此元素的相应y值。

#3

If you mean, that your vector is something like float vector[3]; then vector[1] references the second value in the array, said your Y coordinate of the vector.

如果你的意思是,你的向量就像浮动向量[3];然后vector [1]引用数组中的第二个值,表示向量的Y坐标。

#4

How do you like this code:

你喜欢这段代码:

#include <iostream>
#include <algorithm>

using namespace std;

class Vector3
{
public:
    int x;
    int y;
    int z;

    enum SearchType
    {
        XY, YZ, XZ
    };

    static SearchType searchType;

    Vector3(int x = 0, int y = 0, int z = 0)
        : x(x), y(y), z(z)
    {
    }

    bool operator == (const Vector3 & vec)
    {
        switch(searchType)
        {
            case XY: return (x == vec.x) && (y == vec.y);
            case YZ: return (y == vec.y) && (z == vec.z);
            case XZ: return (x == vec.x) && (z == vec.z);
        }
        return false;
    }
};

Vector3::SearchType Vector3::searchType = XY;

int main()
{
    Vector3 * array = new Vector3 [100];

    array[57].x = 5;
    array[57].y = 100;
    array[57].z = 6;

    Vector3::searchType = Vector3::XZ; // Specify find type as "XZ"
    Vector3 * vec = std::find(array, array+100, Vector3(5,0,6));

    if (vec != array+100)
    {
        cout << "Value for X == 5 and Z == 6 is in "
             << (vec-array) << " item and it eq " << (*vec).y;
    }
}

#5

-1

Please, NEVER EVER perform a search on an unsorted array/vector. Even if it has only 100 elements today, it might become 100000 tomorrow. Take a look at Wiki Sorting Algorithm, some of them are easy to understand and implement. Then look at Wiki Binary search. I would start with quick sort, which also gives you a good idea how binary search works. Believe me, you will thank me later.

请永远不要在未排序的数组/向量上执行搜索。即使它今天只有100个元素,它明天可能会变成100000个。看看Wiki排序算法,其中一些很容易理解和实现。然后看看Wiki Binary搜索。我将从快速排序开始,这也让您了解二进制搜索的工作原理。相信我,你以后会感谢我。

#1