I'm using c++ in visual studio and i have an algorithm that creates an image for the n-body simulation problem. the algorithm itself works however i need to store the image to be able to prove that it works. i have tried a lot of different ways (which have been commented out in the code), to try to achieve this. i am not very familiar with c++ and the code was given to me so any help or advice at all would be greatly appreciated.
the function where i try to store the image is the PrintParticle() function:
#include "stdafx.h"
#include <iostream>
#include <ctime>
#include <math.h>
#include <cstdio>
#include <cstdlib>
#include <fstream>
#include <windows.h>
using namespace std;
#define N 100
#define G 6.673e-11
#define TIMESTAMP 1e11
struct Particle {
double rx, ry;//position components
double vx, vy;//velocity components
double fx, fy;//force components
double mass;//mass of the particle
};
Particle Update(Particle p, double timestamp)
{
p.vx += timestamp*p.fx / p.mass;
p.vy += timestamp*p.fy / p.mass;
p.rx += timestamp*p.vx;
p.ry += timestamp*p.vy;
return p;
}
void PrintParticle(Particle p)
{
ofstream fout("particle.jpg");
fout << ("rx == %f ry == %f vx == %f vy == %f mass == %f\n", p.rx, p.ry, p.vx, p.vy, p.mass)<< endl;
fout.close();
//FILE *f = fopen("particle.ppm", "w"); // Write image to PPM file.
//fprintf(f, "rx == %f ry == %f vx == %f vy == %f mass == %f\n", p.rx, p.ry, p.vx, p.vy, p.mass);
//string filename = "/Users/Tasha/Documents/Visual Studio 2015/Projects/n-bodySim/n-bodySim";
//("rx == %f ry == %f vx == %f vy == %f mass == %f\n", p.rx, p.ry, p.vx, p.vy, p.mass)->WriteImage(filename);
}
//Reset the forces on particle
Particle ResetForce(Particle p)
{
p.fx = 0.0;
p.fy = 0.0;
return p;
}
//Add force to particle a by particle b
Particle AddForce(Particle a, Particle b)
{
double EPS = 3E4; // softening parameter (just to avoid infinities)
double dx = b.rx - a.rx;
double dy = b.ry - a.ry;
double dist = sqrt(dx*dx + dy*dy);
double F = (G * a.mass * b.mass) / (dist*dist + EPS*EPS);
a.fx += F * dx / dist;
a.fy += F * dy / dist;
return a;
}
int main()
{
Particle particles[N];
srand(time(NULL));
//randomly generating N Particles
for (int i = 0; i < N; i++) {
double rx = 1e18*exp(-1.8)*(.5 - rand());
particles[i].rx = rx;
double ry = 1e18*exp(-1.8)*(.5 - rand());
particles[i].ry = ry;
double vx = 1e18*exp(-1.8)*(.5 - rand());
particles[i].vx = vx;
double vy = 1e18*exp(-1.8)*(.5 - rand());
particles[i].vy = vy;
double mass = 1.98892e30*rand() * 10 + 1e20;
particles[i].mass = mass;
}
int numberofiterations = 10;
int count = 0;
while (count < numberofiterations) {
for (int i = 0; i < N; i++)
{
particles[i] = ResetForce(particles[i]);
for (int j = 0; j < N; j++)
{
if (i != j)
{
particles[i] = AddForce(particles[i], particles[j]);
}
}
}
//loop again to update the time stamp here
for (int i = 0; i < N; i++)
{
particles[i] = Update(particles[i], TIMESTAMP);
}
for (int i = 0; i < N; i++)
{
PrintParticle(particles[i]);
}
count++;
}
return 0;
}
