Question

I am quite new at programming in C++… I started out programming in C# a year ago so I’m failing on some really basic stuff… I think…
I created a class called vector that is a point in 3d space the header of which looks like this:

class vec3
{
    double x, y, z;
public:
    vec3();
    vec3(double x, double y, double z);
    double calculateLLength(void);
    double distance(double x1, double y1, double z1);
    double distance(const vec3 &vec);
    ~vec3(void);
};

after this I was supposed to write a class called sphere which centerpoint is
a vector from my vector class which looks lite this (sphere header):

#pragma once
#include "vec3.h"
class Sphere
{
    vec3 center1;
    double x, y, z;
    double radius1;
    static const double PI;

public:

    //constructs
    Sphere(double x, double y, double z, double radius);
    Sphere(vec3 center1, double radius);
    //Methods
    bool inside(const vec3 &center);
    bool overlap(const Sphere &sphere);
    double area();
    double volume();
    ~Sphere(void);
};

the error I get is:

error LNK1120: 1 unresolved externals

I tried to Google this and spent most of my Saturday trying to fix it but can’t….

(here is the cpp files if anyone needs them!)

Sphere.cpp:

#include "StdAfx.h"
#include "Sphere.h"
#include "vec3.h"
#include <math.h>

const double Sphere::PI = 3.1415926535;
Sphere::Sphere(double centerX, double centerY, double centerZ, double radius)
{
    vec3 center(centerX, centerY, centerZ);
    radius1 = radius;
}

Sphere::Sphere(vec3 center, double radius)
{
    center1 = center;
    radius1 = radius;
}
bool Sphere::inside(const vec3 &center)
{
    if(radius1 < center1.distance(center))
        return false;
    else
        return true;
}
bool Sphere::overlap(const Sphere &sphere)
{
    if(this->center1.distance(sphere.center1) < radius1 + sphere.radius1)
        return true;
    else 
        return false;
}
double Sphere::area()
{
}

double Sphere::volume()
{
}

Sphere::~Sphere(void)
{
}

vec3.cpp:

#include "StdAfx.h"
#include "vec3.h"
#include <math.h>


vec3::vec3(double x, double y, double z)
{
    this->x=x;
    this->y=y;
    this->z=z;
}

double vec3::calculateLLength()
{
    return sqrt((x*x) + (y*y) + (z*z));
}

double vec3::distance(double x1, double y1, double z1)
{
    return sqrt( ((this->x - x1)*(this->x - x1)) + ((this->y - y1)*(this->y - y1)) + ((this->z - z1)*(this->z - z1)) );
}

double vec3::distance(const vec3 &vec)
{
    return sqrt( ((this->x - vec.x)*(this->x - vec.x)) + ((this->y - vec.y)*(this->y - vec.y)) + ((this->z - vec.z)*(this->z - vec.z)) );
}

vec3::~vec3(void)
{
}

Answer 1

The issue is you have declared default constructor of vec3 but you haven’t provide a definition for it. Add below code to vec3.cpp:

vec3.cpp:

vec3::vec3()
:x(0),y(0),z(0)
{
}

Side note, Sphere::area and Sphere::volume need to return value as they are declare to return double:

double Sphere::area()
{
   return 0.0;
}

double Sphere::volume()
{
   return 0.0;
}