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#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL2_gfxPrimitives.h>
#define FRAME_DELAY 5
#define WINDOW_WIDTH 648
#define WINDOW_HEIGHT 480
#define CIRCLE_RAD 100
#define CIRCLE_DIAMETER (CIRCLE_RAD * 2)
#define HISTORY_SIZE (WINDOW_WIDTH - CIRCLE_DIAMETER)
int g_history[HISTORY_SIZE] = {0};
double g_angle = 0.0;
int g_circle_count = 1;
bool g_pause = false;
bool g_running = true;
void reset_history(void)
{
for (size_t i = 0; i < HISTORY_SIZE; i++)
g_history[i] = WINDOW_HEIGHT;
}
int main(void)
{
reset_history();
if (SDL_Init(SDL_INIT_VIDEO) != 0)
exit(1);
SDL_Window *window = SDL_CreateWindow(
"fourier-series-viz",
SDL_WINDOWPOS_UNDEFINED,
SDL_WINDOWPOS_UNDEFINED,
WINDOW_WIDTH,
WINDOW_HEIGHT,
0
);
if (window == NULL)
exit(1);
SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, 0);
if (renderer == NULL)
exit(1);
while (g_running)
{
SDL_Event e;
while (SDL_PollEvent(&e))
{
switch (e.type)
{
case SDL_QUIT:
g_running = false;
break;
case SDL_KEYDOWN:
switch (e.key.keysym.sym)
{
case SDLK_q:
case SDLK_ESCAPE:
g_running = false;
break;
case SDLK_p:
case SDLK_SPACE:
g_pause = !g_pause;
break;
case SDLK_j:
case SDLK_MINUS:
g_circle_count--;
if (g_circle_count < 1)
g_circle_count = 1;
reset_history();
break;
case SDLK_k:
case SDLK_EQUALS:
g_circle_count++;
reset_history();
break;
}
}
}
if (g_pause)
{
SDL_Delay(FRAME_DELAY);
continue;
}
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
SDL_RenderClear(renderer);
/* SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255); */
/*
** n = range(1, inf, 2)
**
** 4 * sin(n * theta)
** -----------------
** pi
**
*/
double sum_x = 0.0;
double sum_y = 0.0;
for (int circle_num = 0; circle_num < g_circle_count; circle_num++)
{
int factor = 1 + circle_num * 2;
int radius = (CIRCLE_RAD - 25) * 4 / (factor * M_PI);
double x = radius * cos(factor * g_angle);
double y = radius * sin(factor * g_angle);
int center_x = CIRCLE_RAD + sum_x;
int center_y = WINDOW_HEIGHT / 2 + sum_y;
aacircleColor(renderer, center_x, center_y, radius, 0xffffffff);
filledCircleColor(renderer, center_x + x, center_y + y, 3, 0xffffffff);
sum_x += x;
sum_y += y;
}
g_angle += 0.01;
memmove(g_history + 1, g_history, sizeof(g_history[0]) * (HISTORY_SIZE - 1));
g_history[0] = sum_y;
for (size_t i = 0; i < HISTORY_SIZE; i++)
{
SDL_RenderDrawPoint(
renderer,
CIRCLE_DIAMETER + i + 10,
WINDOW_HEIGHT / 2 + g_history[i]
);
}
SDL_RenderPresent(renderer);
SDL_Delay(FRAME_DELAY);
}
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
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