Solar System Simulation

/// Solar System Simulation by oliver @pixelchipcode
/// This simulation creates a pseudo-3D solar system with planets orbiting around a sun.
/// The user can rotate, tilt, and zoom the camera to explore the system, while planets
/// are rendered with proper depth sorting for occlusion effects, meaning planets in
/// front of the sun are drawn on top, and those behind are occluded.
///
/// Key Features:
/// - **Pseudo-3D Camera**: Camera movement allows for dynamic rotation, tilt, and zoom.
/// - **Planet Occlusion**: Planets are depth sorted to render behind or in front of the sun.
/// - **Interactive System**: Planets and the sun are clickable, displaying relevant data like
///   orbit radius, size, and orbital period.
/// - **Dynamic Orbits**: Orbits can be toggled on or off via spacebar, adjusting planet speeds.
/// - **Text Display**: When clicking on a planet or the sun, text information is displayed
///   dynamically, fading out after a few seconds.
/// - **Ease-based Motion**: Smooth transitions in camera angles, zoom, and planet orbits.
///
/// Key Constants:
/// - **NUM_PLANETS**: Total number of planets in the simulation.
/// - **SUN_SIZE**: Size of the central star (sun).
/// - **SUN_COLOR**: Color of the sun.
/// - **ORBIT_COLOR**: Color for drawing the orbital paths.
///
/// This system demonstrates occlusion rendering, interactive celestial bodies, and smooth
/// pseudo-3D camera controls, making it an excellent example of dynamic 3D-like simulations
/// in a 2D environment.

/// Create Event
// Constants and configuration
#macro NUM_PLANETS 10
#macro SUN_SIZE 30
#macro SUN_COLOR make_color_rgb(255, 208, 21)
#macro BACKGROUND_COLOR make_color_rgb(37, 38, 42)
#macro FONT_COLOR make_color_rgb(192, 191, 193)
#macro ORBIT_COLOR make_color_rgb(96, 99, 101)

// Arrays for names and colors
star_names = ["Proxima Centauri", "Sirius", "Vega", "Altair", "Deneb"];
planet_names = ["Kepler-22b", "Proxima Centauri b", "TRAPPIST-1d", "Gliese 581c", "HD 209458b"];
planet_colors = [
    make_color_rgb(239, 52, 36),   // Red
    make_color_rgb(254, 254, 194), // Light Yellow
    make_color_rgb(109, 72, 205),  // Purple
    make_color_rgb(252, 145, 65)   // Orange
];

// Camera and simulation control
view_angle = 0;
target_view_angle = 0;
tilt_angle = 0;
target_tilt_angle = 0;
zoom = 1;
target_zoom = 1;
orbits_active = false;

// Text display variables
text_to_display = "";
text_index = 0;
is_displaying_text = false;
text_display_timer = 0;

// Sun properties
sun_name = star_names[irandom(array_length(star_names) - 1)];

// Initialize planets array
planets = array_create(NUM_PLANETS);

// Function to initialize planets
function initialize_planets() {
    var previous_orbit_radius = 0;

    for (var i = 0; i < NUM_PLANETS; i++) {
        var planet_name = planet_names[irandom(array_length(planet_names) - 1)];
        var orbital_period = irandom_range(200, 1000);
        var planet_size = random_range(5, 10);

        var planet_orbit_radius = (i == 0)
            ? random_range(50, 100)
            : previous_orbit_radius + planets[i - 1].size + planet_size + random_range(20, 40);

        previous_orbit_radius = planet_orbit_radius;

        planets[i] = {
            name: planet_name,
            orbit_radius: planet_orbit_radius,
            orbit_speed: random_range(0.5, 1.5),
            angle: random(360),
            color: planet_colors[i % array_length(planet_colors)],
            size: planet_size,
            current_speed: 0,
            target_speed: 0,
            orbital_period: orbital_period
        };
    }
}

// Function to determine if a point is in front of the sun
function is_point_in_front(dist, angle, _tilt_angle) {
    var cy = room_height / 2;
    return (cy + lengthdir_y(dist, angle) * dcos(_tilt_angle) > cy);
}

// Function to sort planets by depth
function sort_planets_by_depth() {
    array_sort(planets, function(a, b) {
        var cy = room_height / 2;
        var y1 = cy + lengthdir_y(a.orbit_radius * zoom, a.angle + view_angle) * dcos(tilt_angle);
        var y2 = cy + lengthdir_y(b.orbit_radius * zoom, b.angle + view_angle) * dcos(tilt_angle);
        return sign(y1 - y2);
    });
}

// Function to get clicked object
function get_clicked_object(mx, my) {
    var cx = room_width / 2;
    var cy = room_height / 2;

    // Sort planets by depth before checking clicks
    sort_planets_by_depth();

    // Check planets from front to back
    for (var i = NUM_PLANETS - 1; i >= 0; i--) {
        var planet = planets[i];
        var dist = planet.orbit_radius * zoom;
        var angle = planet.angle + view_angle;
        var x_rot = cx + lengthdir_x(dist, angle);
        var y_rot = cy + lengthdir_y(dist, angle);
        var ny = cy + (y_rot - cy) * dcos(tilt_angle);

        if (point_distance(mx, my, x_rot, ny) <= planet.size * zoom) {
            return {
                type: "planet",
                name: planet.name,
                orbit_radius: planet.orbit_radius,
                orbital_period: planet.orbital_period,
                size: planet.size
            };
        }
    }

    // Check if sun was clicked (only if no planet was clicked)
    if (point_distance(mx, my, cx, cy) <= SUN_SIZE * zoom) {
        return {
            type: "sun",
            name: sun_name,
            size: SUN_SIZE
        };
    }
    return noone;
}

// Function to display object info
function display_object_info(obj) {
    if (obj == noone) return;

    if (obj.type == "sun") {
        text_to_display = obj.name + "\nSun Size: " + string(obj.size);
    } else if (obj.type == "planet") {
        text_to_display = obj.name + "\n" +
                          "Orbit Radius: " + string(obj.orbit_radius) + "\n" +
                          "Orbital Period: " + string(obj.orbital_period) + " days\n" +
                          "Size: " + string(obj.size);
    }
    text_index = 1;
    is_displaying_text = true;
    text_display_timer = room_speed * 3;
}

// Initialize planets
initialize_planets();

/// Step Event
var ease_factor = 0.05;

// Toggle orbits
if (keyboard_check_pressed(vk_space)) {
    orbits_active = !orbits_active;
    for (var i = 0; i < NUM_PLANETS; i++) {
        planets[i].target_speed = orbits_active ? planets[i].orbit_speed : 0;
    }
}

// Update planet speeds and positions
for (var i = 0; i < NUM_PLANETS; i++) {
    var planet = planets[i];
    planet.current_speed = lerp(planet.current_speed, planet.target_speed, ease_factor);
    planet.angle += planet.current_speed;
}

// Camera controls
var rotate_speed = 1;
var tilt_speed = 1;
var zoom_speed = 0.05;

if (keyboard_check(vk_left)) target_view_angle -= rotate_speed;
if (keyboard_check(vk_right)) target_view_angle += rotate_speed;
if (keyboard_check(vk_up)) target_tilt_angle = min(target_tilt_angle + tilt_speed, 89);
if (keyboard_check(vk_down)) target_tilt_angle = max(target_tilt_angle - tilt_speed, -89);
if (keyboard_check(vk_pageup)) target_zoom = min(target_zoom + zoom_speed, 2);
if (keyboard_check(vk_pagedown)) target_zoom = max(target_zoom - zoom_speed, 0.2);

view_angle = lerp(view_angle, target_view_angle, ease_factor);
tilt_angle = lerp(tilt_angle, target_tilt_angle, ease_factor);
zoom = lerp(zoom, target_zoom, ease_factor);

// Text display logic
if (is_displaying_text) {
    if (text_index < string_length(text_to_display)) {
        text_index++;
    } else if (text_display_timer > 0) {
        text_display_timer--;
    } else {
        is_displaying_text = false;
    }
}

/// Draw Event
draw_clear(BACKGROUND_COLOR);

var cx = room_width / 2;
var cy = room_height / 2;

// Draw text
if (is_displaying_text) {
    draw_set_color(FONT_COLOR);
    draw_text(20, 20, string_copy(text_to_display, 1, text_index));
}

// Draw orbits behind the sun
draw_set_color(ORBIT_COLOR);
for (var i = 0; i < NUM_PLANETS; i++) {
    var planet = planets[i];
    var dist = planet.orbit_radius * zoom;

    for (var angle = 0; angle < 360; angle += 5) {
        var angle_current = angle + view_angle;
        var angle_next = angle_current + 5;

        if (!is_point_in_front(dist, angle_current, tilt_angle)) {
            var x1 = cx + lengthdir_x(dist, angle_current);
            var y1 = cy + lengthdir_y(dist, angle_current) * dcos(tilt_angle);
            var x2 = cx + lengthdir_x(dist, angle_next);
            var y2 = cy + lengthdir_y(dist, angle_next) * dcos(tilt_angle);
            draw_line(x1, y1, x2, y2);
        }
    }
}

// Draw planets behind the sun
sort_planets_by_depth();
for (var i = 0; i < NUM_PLANETS; i++) {
    var planet = planets[i];
    var dist = planet.orbit_radius * zoom;
    var angle = planet.angle + view_angle;
    var x_rot = cx + lengthdir_x(dist, angle);
    var y_rot = cy + lengthdir_y(dist, angle);
    var ny = cy + (y_rot - cy) * dcos(tilt_angle);

    if (!is_point_in_front(dist, angle, tilt_angle)) {
        draw_set_color(planet.color);
        draw_circle(x_rot, ny, planet.size * zoom, false);
    }
}

// Draw the sun
draw_set_color(SUN_COLOR);
draw_circle(cx, cy, SUN_SIZE * zoom, false);

// Draw orbits in front of the sun
draw_set_color(ORBIT_COLOR);
for (var i = 0; i < NUM_PLANETS; i++) {
    var planet = planets[i];
    var dist = planet.orbit_radius * zoom;

    for (var angle = 0; angle < 360; angle += 5) {
        var angle_current = angle + view_angle;
        var angle_next = angle_current + 5;

        if (is_point_in_front(dist, angle_current, tilt_angle)) {
            var x1 = cx + lengthdir_x(dist, angle_current);
            var y1 = cy + lengthdir_y(dist, angle_current) * dcos(tilt_angle);
            var x2 = cx + lengthdir_x(dist, angle_next);
            var y2 = cy + lengthdir_y(dist, angle_next) * dcos(tilt_angle);
            draw_line(x1, y1, x2, y2);
        }
    }
}

// Draw planets in front of the sun
for (var i = 0; i < NUM_PLANETS; i++) {
    var planet = planets[i];
    var dist = planet.orbit_radius * zoom;
    var angle = planet.angle + view_angle;
    var x_rot = cx + lengthdir_x(dist, angle);
    var y_rot = cy + lengthdir_y(dist, angle);
    var ny = cy + (y_rot - cy) * dcos(tilt_angle);

    if (is_point_in_front(dist, angle, tilt_angle)) {
        draw_set_color(planet.color);
        draw_circle(x_rot, ny, planet.size * zoom, false);
    }
}

// Handle clicks
if (mouse_check_button_pressed(mb_left)) {
    var clicked_object = get_clicked_object(mouse_x, mouse_y);
    if (clicked_object != noone) {
        display_object_info(clicked_object);
    }
}