Question

For my game, I need to find the distance between two objects at certain times. My question is simply can the findDistance function be improved? I don’t seem to have any issues, I’m only curious if it could have been done better. Also, if I were to do this in a 3D setting how would I go about calculating it since there is another axis?

#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;
}

Other than replacing pos(x,2) with x*x, this cannot be optimized and remain generic/accurate, but if you don’t need generic, it can be faster:

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;
}