chore: clean recommit

Examples/Shapes/DoublePendulum.cs

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+/*******************************************************************************************
+*
+*   raylib [shapes] example - double pendulum
+*
+*   Example complexity rating: [★★☆☆] 2/4
+*
+*   Example originally created with raylib 5.5, last time updated with raylib 5.5
+*
+*   Example contributed by JoeCheong (@Joecheong2006) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   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) 2025 JoeCheong (@Joecheong2006)
+*
+********************************************************************************************/
+
+using System;
+using System.Numerics;
+using static Raylib_cs.Raylib;
+
+namespace Examples.Shapes;
+
+public partial class DoublePendulum : IExample
+{
+    private const int screenWidth = 800;
+    private const int screenHeight = 450;
+
+    // Constant for Simulation
+    private const int SIMULATION_STEPS = 30;
+    private const float G = 9.81f;
+
+    public string Name => "Shapes / Double Pendulum";
+
+    public string Title => "raylib [shapes] example - double pendulum";
+
+    public ConfigFlags ConfigFlags => ConfigFlags.HighDpiWindow;
+
+    // Simulation Parameters
+    private float l1, m1, theta1, w1;
+    private float l2, m2, theta2, w2;
+    private float lengthScaler;
+    private float totalM;
+
+    private Vector2 previousPosition;
+
+    // Scale length
+    private float L1;
+    private float L2;
+
+    // Draw parameters
+    private float lineThick, trailThick;
+    private float fateAlpha;
+
+    // Create framebuffer
+    private RenderTexture2D target;
+
+    // Calculate pendulum end point
+    private static Vector2 CalculatePendulumEndPoint(float l, float theta)
+    {
+        return new(10 * l * MathF.Sin(theta), 10 * l * MathF.Cos(theta));
+    }
+
+    // Calculate double pendulum end point
+    private static Vector2 CalculateDoublePendulumEndPoint(float l1, float theta1, float l2, float theta2)
+    {
+        Vector2 endpoint1 = CalculatePendulumEndPoint(l1, theta1);
+        Vector2 endpoint2 = CalculatePendulumEndPoint(l2, theta2);
+        return new(endpoint1.X + endpoint2.X, endpoint1.Y + endpoint2.Y);
+    }
+
+    public void Init()
+    {
+        // Simulation Parameters
+        l1 = 15.0f; m1 = 0.2f; theta1 = DEG2RAD * 170; w1 = 0;
+        l2 = 15.0f; m2 = 0.1f; theta2 = DEG2RAD * 0; w2 = 0;
+        lengthScaler = 0.1f;
+        totalM = m1 + m2;
+
+        previousPosition = CalculateDoublePendulumEndPoint(l1, theta1, l2, theta2);
+        previousPosition.X += ((float)screenWidth / 2);
+        previousPosition.Y += ((float)screenHeight / 2 - 100);
+
+        // Scale length
+        L1 = l1 * lengthScaler;
+        L2 = l2 * lengthScaler;
+
+        // Draw parameters
+        lineThick = 20; trailThick = 2;
+        fateAlpha = 0.01f;
+
+        // Create framebuffer
+        target = LoadRenderTexture(screenWidth, screenHeight);
+        SetTextureFilter(target.Texture, TextureFilter.Bilinear);
+    }
+
+    public void Update()
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        float dt = GetFrameTime();
+        float step = dt / SIMULATION_STEPS, step2 = step * step;
+
+        // Update Physics - larger steps = better approximation
+        for (int i = 0; i < SIMULATION_STEPS; i++)
+        {
+            float delta = theta1 - theta2;
+            float sinD = MathF.Sin(delta), cosD = MathF.Cos(delta), cos2D = MathF.Cos(2 * delta);
+            float ww1 = w1 * w1, ww2 = w2 * w2;
+
+            // Calculate a1
+            float a1 = (-G * (2 * m1 + m2) * MathF.Sin(theta1)
+                         - m2 * G * MathF.Sin(theta1 - 2 * theta2)
+                         - 2 * sinD * m2 * (ww2 * L2 + ww1 * L1 * cosD))
+                        / (L1 * (2 * m1 + m2 - m2 * cos2D));
+
+            // Calculate a2
+            float a2 = (2 * sinD * (ww1 * L1 * totalM
+                         + G * totalM * MathF.Cos(theta1)
+                         + ww2 * L2 * m2 * cosD))
+                        / (L2 * (2 * m1 + m2 - m2 * cos2D));
+
+            // Update thetas
+            theta1 += w1 * step + 0.5f * a1 * step2;
+            theta2 += w2 * step + 0.5f * a2 * step2;
+
+            // Update omegas
+            w1 += a1 * step;
+            w2 += a2 * step;
+        }
+
+        // Calculate position
+        Vector2 currentPosition = CalculateDoublePendulumEndPoint(l1, theta1, l2, theta2);
+        currentPosition.X += (float)screenWidth / 2;
+        currentPosition.Y += (float)screenHeight / 2 - 100;
+
+        // Draw to render texture
+        BeginTextureMode(target);
+        // Draw a transparent rectangle - smaller alpha = longer trails
+        DrawRectangle(0, 0, screenWidth, screenHeight, Fade(Color.Black, fateAlpha));
+
+        // Draw trail
+        DrawCircleV(previousPosition, trailThick, Color.Red);
+        DrawLineEx(previousPosition, currentPosition, trailThick * 2, Color.Red);
+        EndTextureMode();
+
+        // Update previous position
+        previousPosition = currentPosition;
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+        ClearBackground(Color.Black);
+
+        // Draw trails texture
+        DrawTextureRec(target.Texture, new Rectangle(0, 0, (float)target.Texture.Width, (float)-target.Texture.Height), new Vector2(0, 0), Color.White);
+
+        // Draw double pendulum
+        DrawRectanglePro(new Rectangle(screenWidth / 2.0f, screenHeight / 2.0f - 100, 10 * l1, lineThick),
+            new Vector2(0, lineThick * 0.5f), 90 - RAD2DEG * theta1, Color.RayWhite);
+
+        Vector2 endpoint1 = CalculatePendulumEndPoint(l1, theta1);
+        DrawRectanglePro(new Rectangle(screenWidth / 2.0f + endpoint1.X, screenHeight / 2.0f - 100 + endpoint1.Y, 10 * l2, lineThick),
+            new Vector2(0, lineThick * 0.5f), 90 - RAD2DEG * theta2, Color.RayWhite);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    public void Unload()
+    {
+        UnloadRenderTexture(target);
+    }
+
+    public static int Main()
+    {
+        // Initialization
+        //--------------------------------------------------------------------------------------
+        SetConfigFlags(ConfigFlags.HighDpiWindow);
+        InitWindow(screenWidth, screenHeight, "raylib [shapes] example - double pendulum");
+
+        SetTargetFPS(60);
+        //--------------------------------------------------------------------------------------
+
+        var game = new DoublePendulum();
+        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;
+    }
+}