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// Emptyness? Awesome.
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h"
#include <vector>
#include <utility>
#include <sstream>
#include <iostream>
typedef float real;
struct body
{
real x;
real y;
real vx;
real vy;
body(real _x, real _y)
{
x = _x;
y = _y;
vx = 0.0f;
vy = 0.0f;
}
};
void body_force(std::vector<body>& bodies, real timestep)
{
const real softening = 10.0f;
#pragma omp parallel for schedule(dynamic)
for (int i = 0; i < bodies.size(); i++)
{
real fx = 0.0f;
real fy = 0.0f;
for (int j = 0; j < bodies.size(); j++)
{
if (i == j)
{
continue;
}
real dx = bodies[j].x - bodies[i].x;
real dy = bodies[j].y - bodies[i].y;
real dist_sqr = dx * dx + dy * dy + softening;
real inv_dist = 1.0f / sqrtf(dist_sqr);
real inv_dist_3 =
(
inv_dist *
inv_dist *
inv_dist
);
fx += dx * inv_dist_3;
fy += dy * inv_dist_3;
}
bodies[i].vx += timestep * fx;
bodies[i].vy += timestep * fy;
}
}
// Entry point for the software renderer.
int main(int argc, char** argv)
{
std::vector<body> bodies;
int x_res = 700;
int y_res = 700;
unsigned char* img_data = (unsigned char*)malloc(x_res * y_res * 3 * sizeof(unsigned char));
int stride_in_bytes = x_res * 3;
const real xr = 1000.0f;
const real yr = 1000.0f;
for (int i = 0; i < 20000; i++)
{
real r1 = float(rand()) / float(RAND_MAX) * 2.0f - 1.0f;
real r2 = float(rand()) / float(RAND_MAX) * 2.0f - 1.0f;
real angx = cos(r1 * 2.0f * M_PI);
real angy = sin(r1 * 2.0f * M_PI);
bodies.push_back(body(angx * r2 * xr, angy * r2 * yr));
}
for (int i = 0; i < 3600; i++)
{
memset(img_data, 0, x_res * y_res * 3 * sizeof(unsigned char));
body_force(bodies, 5.0f);
for (int i = 0; i < bodies.size(); i++)
{
body& bi = bodies[i];
bi.x += bi.vx;
bi.y += bi.vy;
int x = bi.x / 10.0f + x_res / 2;
int y = bi.y / 10.0f + y_res / 2;
if (x >= 0 && x < x_res && y >= 0 && y < y_res)
{
img_data[y * stride_in_bytes + x * 3 + 0] = 255;
img_data[y * stride_in_bytes + x * 3 + 1] = 255;
img_data[y * stride_in_bytes + x * 3 + 2] = 255;
}
}
std::stringstream path_builder;
path_builder << "./frame_" << i << ".png";
stbi_write_png(path_builder.str().c_str(), x_res, y_res, 3, img_data, stride_in_bytes);
std::cout << i << std::endl;
}
free(img_data);
return 0;
}
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