From 386504218362232385c61eca6365b95776c60c62 Mon Sep 17 00:00:00 2001
From: Joursoir <chat@joursoir.net>
Date: Tue, 6 Apr 2021 09:47:23 +0000
Subject: add routines for create celestial objects

---
 src/game/CelestialObject.cpp | 74 ++++++++++++++++++++++++++++++++++++++++++++
 src/game/CelestialObject.hpp | 43 +++++++++++++++++++++++++
 2 files changed, 117 insertions(+)
 create mode 100644 src/game/CelestialObject.cpp
 create mode 100644 src/game/CelestialObject.hpp

diff --git a/src/game/CelestialObject.cpp b/src/game/CelestialObject.cpp
new file mode 100644
index 0000000..4016391
--- /dev/null
+++ b/src/game/CelestialObject.cpp
@@ -0,0 +1,74 @@
+#include <GL/glew.h>
+#include <glm/gtc/matrix_transform.hpp>
+#include <glm/gtc/type_ptr.hpp>
+
+#include "CelestialObject.hpp"
+#include "../graphics/Texture.hpp"
+#include "../graphics/Mesh.hpp"
+#include "../objects.hpp"
+
+using namespace glm;
+
+Mesh *CelestialObject::sphere = 0;
+Mesh *CelestialObject::circle = 0;
+
+#define FULL_TURN 360.0f
+
+void CelestialObject::InitializeMesh()
+{
+	sphere = form_sphere(36, 36);
+	circle = form_circle(36);
+}
+
+void CelestialObject::SetPeriod(float a_orbital, float a_rotation)
+{
+	orbital_period = a_orbital;
+	rotation_period = a_rotation;
+	orbital_speed = (a_orbital == 0.0f) ? 0.0f : FULL_TURN / orbital_period;
+	rotation_speed = (a_rotation == 0.0f) ? 0.0f : FULL_TURN / rotation_period;
+}
+
+void CelestialObject::SetRadius(float object_r, float orbital_r)
+{
+	object_radius = object_r;
+	orbital_radius = orbital_r;
+}
+
+void CelestialObject::SetTilt(float angle)
+{
+	tilt_angle = radians(angle);
+}
+
+void CelestialObject::SetPosition(glm::vec3 orbital)
+{
+	orbital_pos = orbital;
+}
+
+void CelestialObject::Draw(float time, float game_speed,
+	unsigned int model_loc)
+{
+	float
+		orb_speed = orbital_speed * game_speed,
+		rot_speed = rotation_speed * game_speed,
+		moveX = sin(radians(time) * orb_speed) * orbital_radius,
+		moveZ = cos(radians(time) * orb_speed) * orbital_radius;
+
+	texture->Bind();
+
+	mat4 sphere_model(1.0f);
+	vec3 pos(orbital_pos.x - moveX, orbital_pos.y, orbital_pos.z - moveZ);
+	sphere_model = translate(sphere_model, pos);
+	sphere_model = rotate(sphere_model, tilt_angle, vec3(1.0f, 0.0f, 0.0f));
+	sphere_model = rotate(sphere_model, radians(time) * rot_speed, vec3(0.0f, 0.0f, 1.0f));
+	sphere_model = scale(sphere_model, vec3(object_radius, object_radius, object_radius));
+	glUniformMatrix4fv(model_loc, 1, GL_FALSE, value_ptr(sphere_model));
+	sphere->Draw();
+
+	if(orbital_radius != 0.0f) {
+		mat4 circle_model(1.0f);
+		circle_model = translate(circle_model, orbital_pos);
+		circle_model = scale(circle_model, vec3(orbital_radius, orbital_radius, orbital_radius));
+		glUniformMatrix4fv(model_loc, 1, GL_FALSE, value_ptr(circle_model));
+		circle->Draw();
+	}
+}
\ No newline at end of file
diff --git a/src/game/CelestialObject.hpp b/src/game/CelestialObject.hpp
new file mode 100644
index 0000000..8997697
--- /dev/null
+++ b/src/game/CelestialObject.hpp
@@ -0,0 +1,43 @@
+#ifndef ENGINE_CELESTIAL_OBJECT_H
+#define ENGINE_CELESTIAL_OBJECT_H
+
+#include <glm/glm.hpp>
+
+class Texture;
+class Mesh;
+
+class CelestialObject {
+	Texture *texture;
+
+	static Mesh *sphere;
+	static Mesh *circle;
+
+	/* time a given astronomical object takes to complete
+	one orbit around another object */
+	float orbital_period;
+	float orbital_speed;
+	float orbital_radius;
+	glm::vec3 orbital_pos;
+
+	/* time that the objects takes to complete a single revolution
+	around its axis of rotation relative to the background stars */
+	float rotation_period;
+	float rotation_speed;
+
+	float object_radius;
+
+	float tilt_angle;
+public:
+	CelestialObject(Texture *t)
+		: texture(t) { }
+	static void InitializeMesh();
+	void SetPeriod(float a_orbital, float a_rotation);
+	void SetRadius(float object_r, float orbital_r);
+	void SetTilt(float angle);
+	void SetPosition(glm::vec3 orbital);
+
+	void Draw(float time, float game_speed, unsigned int model_loc);
+
+};
+
+#endif /* ENGINE_CELESTIAL_OBJECT_H */
-- 
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