79 lines
2.4 KiB
C
79 lines
2.4 KiB
C
|
/*
|
||
|
|
* Copyright (C) 2026 Ortega Froysa, Nicolás <nicolas@ortegas.org>
|
||
|
|
* Author: Ortega Froysa, Nicolás <nicolas@ortegas.org>
|
||
|
|
*
|
||
|
|
* This program is free software: you can redistribute it and/or modify
|
||
|
|
* it under the terms of the GNU General Public License as published by
|
||
|
|
* the Free Software Foundation, either version 3 of the License, or
|
||
|
|
* (at your option) any later version.
|
||
|
|
*
|
||
|
|
* This program is distributed in the hope that it will be useful,
|
||
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
|
|
* GNU General Public License for more details.
|
||
|
|
*
|
||
|
|
* You should have received a copy of the GNU General Public License
|
||
|
|
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include "planet.h"
|
||
|
|
#include <math.h>
|
||
|
|
#include <assert.h>
|
||
|
|
#include <allegro5/allegro_primitives.h>
|
||
|
|
|
||
|
|
#define GRAVITY_CONSTANT 1.0f // Gravitational constant scaled for simulation
|
||
|
|
#define SHIP_MASS 1.0f // Assumed constant ship mass
|
||
|
|
#define MASS_TO_RADIUS 1.5f // Radius scale factor: radius = MASS_TO_RADIUS * mass^(1/3)
|
||
|
|
|
||
|
|
void planet_init(struct planet *planet, float x, float y, float mass) {
|
||
|
|
assert(planet);
|
||
|
|
|
||
|
|
planet->x = x;
|
||
|
|
planet->y = y;
|
||
|
|
planet->mass = mass;
|
||
|
|
planet->radius = MASS_TO_RADIUS * cbrtf(planet->mass);
|
||
|
|
}
|
||
|
|
|
||
|
|
void planet_get_gravity(struct planet *planet, float ship_x, float ship_y,
|
||
|
|
float *accel_x, float *accel_y) {
|
||
|
|
assert(planet);
|
||
|
|
assert(accel_x);
|
||
|
|
assert(accel_y);
|
||
|
|
|
||
|
|
float dx = planet->x - ship_x;
|
||
|
|
float dy = planet->y - ship_y;
|
||
|
|
float distance = sqrtf(dx * dx + dy * dy);
|
||
|
|
|
||
|
|
if(distance < planet->radius) {
|
||
|
|
*accel_x = 0.0f;
|
||
|
|
*accel_y = 0.0f;
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
// F = G * m1 * m2 / r^2
|
||
|
|
float force = GRAVITY_CONSTANT * SHIP_MASS * planet->mass / (distance * distance);
|
||
|
|
|
||
|
|
// a = F / m_ship = G * m_planet / r^2
|
||
|
|
float acceleration = force / SHIP_MASS;
|
||
|
|
|
||
|
|
// Normalize direction and apply acceleration
|
||
|
|
float norm_x = dx / distance;
|
||
|
|
float norm_y = dy / distance;
|
||
|
|
|
||
|
|
*accel_x = norm_x * acceleration;
|
||
|
|
*accel_y = norm_y * acceleration;
|
||
|
|
}
|
||
|
|
|
||
|
|
void planet_draw(struct planet *planet) {
|
||
|
|
assert(planet);
|
||
|
|
|
||
|
|
// Color intensity based on mass (brighter = more massive)
|
||
|
|
float color_scale = fminf(1.0f, planet->mass / 1000.0f);
|
||
|
|
int r = (int)(100 + 155 * color_scale);
|
||
|
|
int g = (int)(100 + 50 * color_scale);
|
||
|
|
int b = (int)(150 - 100 * color_scale);
|
||
|
|
|
||
|
|
al_draw_filled_circle(planet->x, planet->y, planet->radius,
|
||
|
|
al_map_rgb(r, g, b));
|
||
|
|
}
|