Port to C++.

src/planet.cpp

@@ -0,0 +1,57 @@
+/*
+ * 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 <cmath>
+#include <cassert>
+#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)
+
+Planet::Planet(const float x, const float y, const float mass) :
+	pos(x, y), mass(mass), radius(MASS_TO_RADIUS * cbrtf(mass))
+{}
+
+Vec<float> Planet::getGravity(const Ship &ship) const {
+	const Vec<float> distance = this->pos - ship.getPos();
+
+	if(distance.length() < this->radius)
+		return Vec<float>(0, 0);
+
+	// F = G * m1 * m2 / r^2
+	const float force = GRAVITY_CONSTANT * SHIP_MASS * this->mass / (distance.length() * distance.length());
+
+	// a = F / m_ship = G * m_this / r^2
+	const float acceleration = force / SHIP_MASS;
+
+	// Normalize direction and apply acceleration
+	return distance.normalized() * acceleration;
+}
+
+void Planet::draw() {
+	// Color intensity based on mass (brighter = more massive)
+	float color_scale = fminf(1.0f, this->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(this->pos.x, this->pos.y, this->radius,
+						  al_map_rgb(r, g, b));
+}