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feat: add trail

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This commit is contained in:
Alejandro Laguna
2025-11-15 18:29:46 +01:00
parent 90ee367dc6
commit 89fe0e0f65
5 changed files with 107 additions and 64 deletions
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2
include/gfx.hpp
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@@ -2,8 +2,6 @@
#define GFX_UTILS_HPP
#include <SDL3/SDL_render.h>
namespace gfx {
void draw_circle(SDL_Renderer *renderer, int center_x, int center_y, int radius, bool fill);
}
#endif

32
include/sims.hpp
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@@ -1,14 +1,26 @@
#ifndef SIMS_HPP
#define SIMS_HPP
#include <SDL3/SDL_render.h>
#define SIMS_HPP
namespace sims {
typedef struct {
int x;
int y;
int r;
} body;
void two_bodies(SDL_Renderer *r);
}
#include <SDL3/SDL_render.h>
#include <utility>
class Body {
private:
float x;
float y;
float vx = 1;
float vy = 1;
std::pair<float, float> old_positions[100];
public:
SDL_Renderer* renderer;
Body(int x_pos, int y_pos);
void draw_tail();
void live();
};
void two_bodies(SDL_Renderer* r, Body &a, Body &b);
#endif

60
src/gfx/circle.cpp
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@@ -1,39 +1,37 @@
#include <SDL3/SDL_render.h>
namespace gfx {
void draw_circle(SDL_Renderer *renderer, int center_x, int center_y, int radius, bool fill) {
int x = radius;
int y = 0;
int decision = 1 - x;
void draw_circle(SDL_Renderer *renderer, int center_x, int center_y, int radius, bool fill) {
int x = radius;
int y = 0;
int decision = 1 - x;
SDL_SetRenderDrawColor(renderer, 255, 0, 255, 255);
SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
while (x >= y) {
if (fill) {
// Draw horizontal lines across the circle
SDL_RenderLine(renderer, center_x - x, center_y + y, center_x + x, center_y + y);
SDL_RenderLine(renderer, center_x - x, center_y - y, center_x + x, center_y - y);
SDL_RenderLine(renderer, center_x - y, center_y + x, center_x + y, center_y + x);
SDL_RenderLine(renderer, center_x - y, center_y - x, center_x + y, center_y - x);
} else {
// Just draw points for the outline
SDL_RenderPoint(renderer, center_x + x, center_y + y);
SDL_RenderPoint(renderer, center_x - x, center_y + y);
SDL_RenderPoint(renderer, center_x + x, center_y - y);
SDL_RenderPoint(renderer, center_x - x, center_y - y);
SDL_RenderPoint(renderer, center_x + y, center_y + x);
SDL_RenderPoint(renderer, center_x - y, center_y + x);
SDL_RenderPoint(renderer, center_x + y, center_y - x);
SDL_RenderPoint(renderer, center_x - y, center_y - x);
}
while (x >= y) {
if (fill) {
// Draw horizontal lines across the circle
SDL_RenderLine(renderer, center_x - x, center_y + y, center_x + x, center_y + y);
SDL_RenderLine(renderer, center_x - x, center_y - y, center_x + x, center_y - y);
SDL_RenderLine(renderer, center_x - y, center_y + x, center_x + y, center_y + x);
SDL_RenderLine(renderer, center_x - y, center_y - x, center_x + y, center_y - x);
} else {
// Just draw points for the outline
SDL_RenderPoint(renderer, center_x + x, center_y + y);
SDL_RenderPoint(renderer, center_x - x, center_y + y);
SDL_RenderPoint(renderer, center_x + x, center_y - y);
SDL_RenderPoint(renderer, center_x - x, center_y - y);
SDL_RenderPoint(renderer, center_x + y, center_y + x);
SDL_RenderPoint(renderer, center_x - y, center_y + x);
SDL_RenderPoint(renderer, center_x + y, center_y - x);
SDL_RenderPoint(renderer, center_x - y, center_y - x);
}
y++;
if (decision <= 0) {
decision += 2 * y + 1;
} else {
x--;
decision += 2 * (y - x + 1);
}
y++;
if (decision <= 0) {
decision += 2 * y + 1;
} else {
x--;
decision += 2 * (y - x + 1);
}
}
}

30
src/main.cpp
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@@ -27,8 +27,22 @@ bool event_handling(SDL_Event e) {
return false;
}
void sim(SDL_Renderer *r) {
sims::two_bodies(r);
void sim(SDL_Renderer *r, SDL_Event e) {
bool exit = false;
Body body1 = Body(50, 50);
body1.renderer = r;
Body body2 = Body(50, 100);
body2.renderer = r;
while (!exit) {
exit = event_handling(e);
SDL_SetRenderDrawColor(r, 0, 0, 0, 0);
SDL_RenderClear(r);
two_bodies(r, body1, body2);
SDL_RenderPresent(r);
SDL_Delay(16);
}
}
int main() {
@@ -51,17 +65,7 @@ int main() {
SDL_Event e;
bool exit = false;
while (!exit) {
exit = event_handling(e);
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);
SDL_RenderClear(renderer);
sim(renderer);
SDL_RenderPresent(renderer);
SDL_Delay(16);
}
sim(renderer, e);
SDL_Quit();
return 0;

47
src/sims/two_bodies.cpp
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@@ -1,13 +1,44 @@
#include <SDL3/SDL.h>
#include "../../include/gfx.hpp"
#include <SDL3/SDL_log.h>
#include <SDL3/SDL_render.h>
#include "../../include/sims.hpp"
#include "../../include/gfx.hpp"
#include <algorithm>
#include <cmath>
#include <iterator>
#include <utility>
namespace sims {
void two_bodies(SDL_Renderer *r) {
body body1 = {10, 10, 10};
body body2 = {250, 250, 10};
using namespace std;
gfx::draw_circle(r, body1.x, body1.y, body1.r, true);
gfx::draw_circle(r, body2.x, body2.y, body2.r, true);
}
Body::Body(int x_pos, int y_pos) : x(x_pos), y(y_pos) {
fill(begin(old_positions), end(old_positions), make_pair(x, y));
}
void Body::draw_tail() {
size_t n = std::size(old_positions);
for (size_t i = 0; i < n; ++i) {
const auto& p = old_positions[i];
SDL_RenderPoint(renderer, p.first, p.second);
}
for (size_t i = n - 1; i > 0; --i) {
old_positions[i] = old_positions[i - 1];
}
old_positions[0] = {x, y};
}
void Body::live() {
x += vx;
y += sin(x * 0.1);
draw_circle(renderer, x, y, 10, true);
draw_tail();
}
void two_bodies(SDL_Renderer* r, Body& a, Body& b) {
a.live();
b.live();
}