c++ - 计算两个物体之间的距离

Question

对于我的游戏，我需要在特定时间找出两个物体之间的距离。我的问题只是可以改进 findDistance 函数吗？我似乎没有任何问题，我只是好奇它是否可以做得更好。另外，如果我要在 3D 设置中执行此操作，因为还有另一个轴，我将如何计算它？

#include <math.h>
#include <iostream>

struct point{float x, y;};

float findDistance(point &x, point &y)
{
    float distance, tempx, tempy;
    tempx = (x.x - y.x);
    tempx = pow(tempx, 2.0f);
    tempy = (x.y - y.y);
    tempy = pow(tempy, 2.0f);
    distance = tempx + tempy;
    distance = sqrt(distance);
    return distance;
}

int main()
{
    point a, b;
    a.x = -2;
    a.y = -3;
    b.x = -4;
    b.y = 4;

    std::cout << "The distance between point x and y is: " << findDistance(a, b) << std::endl;
    return 0;
}

Answer 1

3d:

float findDistance(point &x, point &y)
{
    float distance, tempx, tempy, tempz;
    tempx = (x.x - y.x);
    tempx = tempx * tempx; //compiler _might_ be able to make this faster
    tempy = (x.y - y.y);
    tempy = tempy * tempy;
    tempz = (x.z - y.z);
    tempz = tempz * tempz;
    distance = tempx + tempy + tempz;
    distance = sqrt(distance);
    return distance;
}

除了将 pos(x,2) 替换为 x*x 之外，这无法优化并保持通用/准确，但如果您不需要通用，它可以更快:

bool distanceLessThan(point &x, point &y, float distance)
{
    float tempx, tempy, tempz, tempd;
    tempx = std::abs(x.x - y.x);
    tempy = std::abs(x.y - y.y);
    tempz = std::abs(x.z - y.z);
    if (tempx + tempy + tempz < distance) //for small distances, don't square
        return true;
    if (tempx + tempy + tempz > distance/2) //for large distances, don't square
        return false;
    tempx = tempx * tempx;
    tempy = tempy * tempy;
    tempz = tempz * tempz;
    tempd = distance * distance; 
    if (tempx + tempy + tempz < tempd)
        return true;
    return false;
}