raylib-cs/Examples/Models/SolarSystem.cs

/*******************************************************************************************
*
*   raylib [models] example - rlgl solar system
*
*   Example complexity rating: [★★★★] 4/4
*
*   NOTE: This example uses [rlgl] module functionality (pseudo-OpenGL 1.1 style coding)
*
*   Example originally created with raylib 2.5, last time updated with raylib 4.0
*
*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
*   BSD-like license that allows static linking with closed source software
*
*   Copyright (c) 2018-2025 Ramon Santamaria (@raysan5)
*
********************************************************************************************/

namespace Examples.Models;

public partial class SolarSystem : IExample
{
    private const int screenWidth = 800;
    private const int screenHeight = 450;

    private const float sunRadius = 4.0f;
    private const float earthRadius = 0.6f;
    private const float earthOrbitRadius = 8.0f;
    private const float moonRadius = 0.16f;
    private const float moonOrbitRadius = 1.5f;

    public string Name => "Models / Solar System";

    public string Title => "raylib [models] example - rlgl solar system";

    private Camera3D camera;

    private float rotationSpeed;

    private float earthRotation;
    private float earthOrbitRotation;
    private float moonRotation;
    private float moonOrbitRotation;

    public void Init()
    {
        // Define the camera to look into our 3d world
        camera = new();
        camera.Position = new Vector3(16.0f, 16.0f, 16.0f); // Camera position
        camera.Target = new Vector3(0.0f, 0.0f, 0.0f);      // Camera looking at point
        camera.Up = new Vector3(0.0f, 1.0f, 0.0f);          // Camera up vector (rotation towards target)
        camera.FovY = 45.0f;                                // Camera field-of-view Y
        camera.Projection = CameraProjection.Perspective;   // Camera projection type

        rotationSpeed = 0.2f;         // General system rotation speed

        earthRotation = 0.0f;         // Rotation of earth around itself (days) in degrees
        earthOrbitRotation = 0.0f;    // Rotation of earth around the Sun (years) in degrees
        moonRotation = 0.0f;          // Rotation of moon around itself
        moonOrbitRotation = 0.0f;     // Rotation of moon around earth in degrees
    }

    public void Update()
    {
        // Update
        //----------------------------------------------------------------------------------
        earthRotation += (5.0f * rotationSpeed);
        earthOrbitRotation += (365 / 360.0f * (5.0f * rotationSpeed) * rotationSpeed);
        moonRotation += (2.0f * rotationSpeed);
        moonOrbitRotation += (8.0f * rotationSpeed);
        //----------------------------------------------------------------------------------

        // Draw
        //----------------------------------------------------------------------------------
        BeginDrawing();
        ClearBackground(Color.RayWhite);

        BeginMode3D(camera);

        Rlgl.PushMatrix();
        // Scale Sun
        Rlgl.Scalef(sunRadius, sunRadius, sunRadius);
        // Draw the Sun
        DrawSphereBasic(Color.Gold);
        Rlgl.PopMatrix();

        Rlgl.PushMatrix();
        // Rotation for Earth orbit around Sun
        Rlgl.Rotatef(earthOrbitRotation, 0.0f, 1.0f, 0.0f);
        // Translation for Earth orbit
        Rlgl.Translatef(earthOrbitRadius, 0.0f, 0.0f);

        Rlgl.PushMatrix();
        // Rotation for Earth itself
        Rlgl.Rotatef(earthRotation, 0.25f, 1.0f, 0.0f);
        // Scale Earth
        Rlgl.Scalef(earthRadius, earthRadius, earthRadius);

        // Draw the Earth
        DrawSphereBasic(Color.Blue);
        Rlgl.PopMatrix();

        // Rotation for Moon orbit around Earth
        Rlgl.Rotatef(moonOrbitRotation, 0.0f, 1.0f, 0.0f);
        // Translation for Moon orbit
        Rlgl.Translatef(moonOrbitRadius, 0.0f, 0.0f);
        // Rotation for Moon itself
        Rlgl.Rotatef(moonRotation, 0.0f, 1.0f, 0.0f);
        // Scale Moon
        Rlgl.Scalef(moonRadius, moonRadius, moonRadius);

        // Draw the Moon
        DrawSphereBasic(Color.LightGray);
        Rlgl.PopMatrix();

        // Some reference elements (not affected by previous matrix transformations)
        DrawCircle3D(
            new Vector3(0.0f, 0.0f, 0.0f),
            earthOrbitRadius,
            new Vector3(1, 0, 0),
            90.0f,
            Fade(Color.Red, 0.5f)
        );
        DrawGrid(20, 1.0f);

        EndMode3D();

        DrawText("EARTH ORBITING AROUND THE SUN!", 400, 10, 20, Color.Maroon);
        DrawFPS(10, 10);

        EndDrawing();
        //----------------------------------------------------------------------------------
    }

    public void Unload()
    {
    }

    // Draw sphere without any matrix transformation
    // NOTE: Sphere is drawn in world position ( 0, 0, 0 ) with radius 1.0f
    private static void DrawSphereBasic(Color color)
    {
        var rings = 16;
        var slices = 16;

        Rlgl.Begin(DrawMode.Triangles);
        Rlgl.Color4ub(color.R, color.G, color.B, color.A);

        for (var i = 0; i < (rings + 2); i++)
        {
            for (var j = 0; j < slices; j++)
            {
                Rlgl.Vertex3f(
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * i)) * MathF.Sin(DEG2RAD * (j * 360 / slices)),
                    MathF.Sin(DEG2RAD * (270 + (180 / (rings + 1)) * i)),
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * i)) * MathF.Cos(DEG2RAD * (j * 360 / slices))
                );
                Rlgl.Vertex3f(
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))) * MathF.Sin(DEG2RAD * ((j + 1) * 360 / slices)),
                    MathF.Sin(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))),
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))) * MathF.Cos(DEG2RAD * ((j + 1) * 360 / slices))
                );
                Rlgl.Vertex3f(
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))) * MathF.Sin(DEG2RAD * (j * 360 / slices)),
                    MathF.Sin(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))),
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))) * MathF.Cos(DEG2RAD * (j * 360 / slices))
                );

                Rlgl.Vertex3f(
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * i)) * MathF.Sin(DEG2RAD * (j * 360 / slices)),
                    MathF.Sin(DEG2RAD * (270 + (180 / (rings + 1)) * i)),
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * i)) * MathF.Cos(DEG2RAD * (j * 360 / slices))
                );
                Rlgl.Vertex3f(
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * (i))) * MathF.Sin(DEG2RAD * ((j + 1) * 360 / slices)),
                    MathF.Sin(DEG2RAD * (270 + (180 / (rings + 1)) * (i))),
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * (i))) * MathF.Cos(DEG2RAD * ((j + 1) * 360 / slices))
                );
                Rlgl.Vertex3f(
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))) * MathF.Sin(DEG2RAD * ((j + 1) * 360 / slices)),
                    MathF.Sin(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))),
                    MathF.Cos(DEG2RAD * (270 + (180 / (rings + 1)) * (i + 1))) * MathF.Cos(DEG2RAD * ((j + 1) * 360 / slices))
                );
            }
        }
        Rlgl.End();
    }

    public static int Main()
    {
        // Initialization
        //--------------------------------------------------------------------------------------
        InitWindow(screenWidth, screenHeight, "raylib [models] example - rlgl solar system");

        SetTargetFPS(60);
        //--------------------------------------------------------------------------------------

        var game = new SolarSystem();
        game.Init();

        // Main game loop
        while (!WindowShouldClose())    // Detect window close button or ESC key
        {
            game.Update();
        }

        game.Unload();

        // De-Initialization
        //--------------------------------------------------------------------------------------
        CloseWindow();        // Close window and OpenGL context
        //--------------------------------------------------------------------------------------

        return 0;
    }
}