Physics-Engine/PhysicsEngine/Core/Program.cs

using System.Numerics;
using Raylib_cs;

namespace PhysicsEngine
{
    class Program
    {
        private static Font robotoFont;
        private static WorldModel world; // Instance of our WorldModel

        static void Main(string[] args)
        {
            Raylib.SetConfigFlags(ConfigFlags.FullscreenMode | ConfigFlags.VSyncHint);
            Raylib.InitWindow(0, 0, "Physics Engine");

            robotoFont = Raylib.LoadFont("Roboto-Regular.ttf");
            Raylib.SetTextureFilter(robotoFont.Texture, TextureFilter.Bilinear);

            Camera camera = new Camera();
            world = new WorldModel(); // Initialize simulation world

            ScenarioLarge();

            const float physicsTimeStep = 1.0f / 60.0f;
            float accumulator = 0.0f;

            // Main loop
            while (!Raylib.WindowShouldClose())
            {
                float frameTime = Raylib.GetFrameTime();
                if (frameTime > 0.25f)
                {
                    frameTime = 0.25f;
                }

                // Update Camera
                camera.Update(frameTime);

                // Update Physics accumulator
                accumulator += frameTime;
                while (accumulator >= physicsTimeStep)
                {
                    UpdatePhysics(physicsTimeStep);
                    accumulator -= physicsTimeStep;
                }

                // Render loop
                Raylib.BeginDrawing();
                Raylib.ClearBackground(MuiDarkColor.BackgroundDefault.ToColor());

                // Draw background screen-space elements (Grid)
                camera.DrawGrid();

                // Draw World Bodies inside the Camera's 2D World Transform
                Raylib.BeginMode2D(camera.RaylibCamera);
                RenderScene();
                Raylib.EndMode2D();

                // Draw UI / HUD elements
                camera.DrawHUD();
                DrawText("Physics Engine", 20, 20, 30, MuiDarkColor.TextPrimary.ToColor());

                Raylib.EndDrawing();
            }

            Raylib.UnloadFont(robotoFont);
            Raylib.CloseWindow();
        }

        public static void DrawText(string text, int posX, int posY, float fontSize, Color color)
        {
            Raylib.DrawTextEx(robotoFont, text, new Vector2(posX, posY), fontSize, 1.0f, color);
        }

        private static void UpdatePhysics(float dt)
        {
            world.Step(dt);
        }

        private static void RenderScene()
        {
            // Iterate and draw all bodies in the world
            foreach (var body in world.Bodies)
            {
                body.Draw();
            }
        }

        private static void Scenario()
        {
            float worldWidth = 12.8f;
            float worldHeight = 7.2f;
            float wallThickness = 1.0f;

            // 1. Static world borders
            Box floor = new Box(new Vector2(worldWidth * 0.5f, worldHeight + (wallThickness * 0.5f)), new Vector2(worldWidth + wallThickness * 2, wallThickness), 0f);
            floor.BaseColor = Color.DarkGray;
            world.AddBody(floor);

            Box ceiling = new Box(new Vector2(worldWidth * 0.5f, -wallThickness * 0.5f), new Vector2(worldWidth + wallThickness * 2, wallThickness), 0f);
            ceiling.BaseColor = Color.DarkGray;
            world.AddBody(ceiling);

            Box leftWall = new Box(new Vector2(-wallThickness * 0.5f, worldHeight * 0.5f), new Vector2(wallThickness, worldHeight + wallThickness * 2), 0f);
            leftWall.BaseColor = Color.DarkGray;
            world.AddBody(leftWall);

            Box rightWall = new Box(new Vector2(worldWidth + wallThickness * 0.5f, worldHeight * 0.5f), new Vector2(wallThickness, worldHeight + wallThickness * 2), 0f);
            rightWall.BaseColor = Color.DarkGray;
            world.AddBody(rightWall);

            // 2. Static ramps and platforms (rotated boxes)
            // Left ramp (slopes up to the right)
            Box leftRamp = new Box(new Vector2(2.5f, 5.5f), new Vector2(4.0f, 0.4f), 0f);
            leftRamp.Rotation = -0.4f; // tilt upward to the right
            leftRamp.BaseColor = Color.Gray;
            world.AddBody(leftRamp);

            // Right ramp (slopes down to the right)
            Box rightRamp = new Box(new Vector2(10.5f, 5.5f), new Vector2(4.0f, 0.4f), 0f);
            rightRamp.Rotation = 0.4f; // tilt downward to the right
            rightRamp.BaseColor = Color.Gray;
            world.AddBody(rightRamp);

            // Floating platform in the middle
            Box platform = new Box(new Vector2(6.4f, 3.5f), new Vector2(3.0f, 0.4f), 0f);
            platform.BaseColor = Color.LightGray;
            world.AddBody(platform);

            // Small static circle bumper near the bottom center
            Circle staticBumper = new Circle(new Vector2(6.4f, 6.0f), 0.3f, 0f);
            staticBumper.BaseColor = Color.Orange;
            world.AddBody(staticBumper);

            // 3. Dynamic bodies – a mix of boxes and circles with varied properties

            // Tall, thin box (will tip over when hitting the ground)
            Box tallBox = new Box(new Vector2(2.0f, 1.0f), new Vector2(0.3f, 1.8f), 30f);
            tallBox.BaseColor = Color.SkyBlue;
            tallBox.Rotation = 0.3f;
            tallBox.AngularVelocity = 0.5f;
            tallBox.Friction = 0.8f;
            tallBox.Restitution = 0.1f;
            world.AddBody(tallBox);

            // Heavy square box
            Box heavyBox = new Box(new Vector2(4.0f, 1.5f), new Vector2(0.8f, 0.8f), 80f);
            heavyBox.BaseColor = Color.DarkGreen;
            heavyBox.Friction = 0.9f;
            heavyBox.Restitution = 0.0f;
            heavyBox.Velocity = new Vector2(1.5f, -1.0f);
            world.AddBody(heavyBox);

            // Long plank (will slide and possibly balance)
            Box plank = new Box(new Vector2(8.0f, 0.5f), new Vector2(2.5f, 0.25f), 25f);
            plank.BaseColor = Color.Brown;
            plank.Rotation = -0.2f;
            plank.AngularVelocity = -0.3f;
            plank.Friction = 0.6f;
            world.AddBody(plank);

            // Bouncy ball (high restitution, low friction)
            Circle bouncyBall = new Circle(new Vector2(9.0f, 1.0f), 0.3f, 5f);
            bouncyBall.BaseColor = Color.Red;
            bouncyBall.Restitution = 0.9f;
            bouncyBall.Friction = 0.05f;
            bouncyBall.Velocity = new Vector2(-30.0f, -20.0f);
            bouncyBall.AngularVelocity = 10f;
            world.AddBody(bouncyBall);

            // Heavy circle (rolls slowly)
            Circle heavyBall = new Circle(new Vector2(5.0f, 0.8f), 0.5f, 40f);
            heavyBall.BaseColor = Color.Purple;
            heavyBall.Friction = 0.7f;
            heavyBall.Restitution = 0.1f;
            heavyBall.Velocity = new Vector2(2.0f, -0.5f);
            world.AddBody(heavyBall);

            // Small fast circle
            Circle fastCircle = new Circle(new Vector2(1.0f, 2.0f), 0.2f, 2f);
            fastCircle.BaseColor = Color.Yellow;
            fastCircle.Restitution = 0.7f;
            fastCircle.Friction = 0.2f;
            fastCircle.Velocity = new Vector2(6.0f, 2.0f);
            world.AddBody(fastCircle);

            // Another box with high drag (will slow down quickly)
            Box dragBox = new Box(new Vector2(10.0f, 2.0f), new Vector2(0.6f, 0.6f), 15f);
            dragBox.BaseColor = Color.Violet;
            dragBox.DragCoefficient = 2.0f;
            dragBox.Velocity = new Vector2(-2.0f, -1.0f);
            dragBox.AngularVelocity = 2.0f;
            world.AddBody(dragBox);

            // Circle with high drag (like a light ball in air)
            Circle dragCircle = new Circle(new Vector2(3.0f, 3.0f), 0.4f, 8f);
            dragCircle.BaseColor = Color.Pink;
            dragCircle.DragCoefficient = 1.5f;
            dragCircle.Velocity = new Vector2(1.0f, 3.0f);
            world.AddBody(dragCircle);

            // A box launched with an impulse at an offset (will spin)
            Box spinningBox = new Box(new Vector2(7.0f, 2.5f), new Vector2(0.5f, 0.5f), 10f);
            spinningBox.BaseColor = Color.Beige;
            spinningBox.ApplyImpulseAtOffset(new Vector2(3.0f, -5.0f), new Vector2(0.25f, 0.0f));
            world.AddBody(spinningBox);

            // A circle launched with angular impulse
            Circle spinningCircle = new Circle(new Vector2(11.0f, 1.0f), 0.35f, 12f);
            spinningCircle.BaseColor = Color.Lime;
            spinningCircle.ApplyImpulseAtOffset(new Vector2(0.0f, -8.0f), new Vector2(0.1f, 0.0f));
            world.AddBody(spinningCircle);
        }

        private static void ScenarioLarge()
        {
            // Larger world dimensions
            float worldWidth = 20.0f;
            float worldHeight = 12.0f;
            float wallThickness = 1.0f;

            // 1. Static world borders
            Box floor = new Box(new Vector2(worldWidth * 0.5f, worldHeight + (wallThickness * 0.5f)), new Vector2(worldWidth + wallThickness * 2, wallThickness), 0f);
            floor.BaseColor = Color.DarkGray;
            world.AddBody(floor);

            Box ceiling = new Box(new Vector2(worldWidth * 0.5f, -wallThickness * 0.5f), new Vector2(worldWidth + wallThickness * 2, wallThickness), 0f);
            ceiling.BaseColor = Color.DarkGray;
            world.AddBody(ceiling);

            Box leftWall = new Box(new Vector2(-wallThickness * 0.5f, worldHeight * 0.5f), new Vector2(wallThickness, worldHeight + wallThickness * 2), 0f);
            leftWall.BaseColor = Color.DarkGray;
            world.AddBody(leftWall);

            Box rightWall = new Box(new Vector2(worldWidth + wallThickness * 0.5f, worldHeight * 0.5f), new Vector2(wallThickness, worldHeight + wallThickness * 2), 0f);
            rightWall.BaseColor = Color.DarkGray;
            world.AddBody(rightWall);

            // 2. Static ramps (angled platforms)
            Box ramp1 = new Box(new Vector2(4.0f, 9.0f), new Vector2(5.0f, 0.4f), 0f);
            ramp1.Rotation = -0.35f;
            ramp1.BaseColor = Color.Gray;
            world.AddBody(ramp1);

            Box ramp2 = new Box(new Vector2(16.0f, 9.0f), new Vector2(5.0f, 0.4f), 0f);
            ramp2.Rotation = 0.35f;
            ramp2.BaseColor = Color.Gray;
            world.AddBody(ramp2);

            // Static horizontal platforms
            Box platform1 = new Box(new Vector2(7.0f, 6.0f), new Vector2(4.0f, 0.4f), 0f);
            platform1.BaseColor = Color.LightGray;
            world.AddBody(platform1);

            Box platform2 = new Box(new Vector2(13.0f, 6.0f), new Vector2(4.0f, 0.4f), 0f);
            platform2.BaseColor = Color.LightGray;
            world.AddBody(platform2);

            // Static vertical pillars to create obstacles
            Box pillar1 = new Box(new Vector2(5.0f, 4.0f), new Vector2(0.3f, 3.0f), 0f);
            pillar1.BaseColor = Color.DarkBrown;
            world.AddBody(pillar1);

            Box pillar2 = new Box(new Vector2(15.0f, 4.0f), new Vector2(0.3f, 3.0f), 0f);
            pillar2.BaseColor = Color.DarkBrown;
            world.AddBody(pillar2);

            // Static circular bumpers
            Circle bumper1 = new Circle(new Vector2(10.0f, 8.0f), 0.4f, 0f);
            bumper1.BaseColor = Color.Orange;
            world.AddBody(bumper1);

            Circle bumper2 = new Circle(new Vector2(10.0f, 3.0f), 0.4f, 0f);
            bumper2.BaseColor = Color.Orange;
            world.AddBody(bumper2);

            Circle bumper3 = new Circle(new Vector2(2.0f, 7.0f), 0.3f, 0f);
            bumper3.BaseColor = Color.Orange;
            world.AddBody(bumper3);

            Circle bumper4 = new Circle(new Vector2(18.0f, 7.0f), 0.3f, 0f);
            bumper4.BaseColor = Color.Orange;
            world.AddBody(bumper4);

            // 3. Dynamic bodies – many with high energy, low damping

            // High restitution balls (bouncy)
            for (int i = 0; i < 6; i++)
            {
                Circle bouncyBall = new Circle(new Vector2(2.0f + i * 3.0f, 1.5f), 0.25f, 3.0f);
                bouncyBall.BaseColor = Color.Red;
                bouncyBall.Restitution = 0.95f;
                bouncyBall.Friction = 0.05f;
                bouncyBall.Velocity = new Vector2((i % 2 == 0 ? 3.0f : -3.0f), -2.0f);
                bouncyBall.AngularVelocity = 5.0f;
                world.AddBody(bouncyBall);
            }

            // Heavy boxes (low restitution, high friction)
            Box heavy1 = new Box(new Vector2(6.0f, 2.0f), new Vector2(1.0f, 0.8f), 60f);
            heavy1.BaseColor = Color.DarkGreen;
            heavy1.Friction = 0.9f;
            heavy1.Restitution = 0.0f;
            heavy1.Velocity = new Vector2(2.0f, -1.0f);
            world.AddBody(heavy1);

            Box heavy2 = new Box(new Vector2(14.0f, 2.0f), new Vector2(1.0f, 0.8f), 60f);
            heavy2.BaseColor = Color.DarkGreen;
            heavy2.Friction = 0.9f;
            heavy2.Restitution = 0.0f;
            heavy2.Velocity = new Vector2(-2.0f, -1.0f);
            world.AddBody(heavy2);

            // Long planks (will slide and rotate)
            Box plank1 = new Box(new Vector2(8.0f, 10.5f), new Vector2(3.0f, 0.3f), 20f);
            plank1.BaseColor = Color.Brown;
            plank1.Rotation = 0.1f;
            plank1.AngularVelocity = -0.4f;
            plank1.Friction = 0.6f;
            plank1.Velocity = new Vector2(1.0f, -0.5f);
            world.AddBody(plank1);

            Box plank2 = new Box(new Vector2(12.0f, 10.5f), new Vector2(3.0f, 0.3f), 20f);
            plank2.BaseColor = Color.Brown;
            plank2.Rotation = -0.1f;
            plank2.AngularVelocity = 0.4f;
            plank2.Friction = 0.6f;
            plank2.Velocity = new Vector2(-1.0f, -0.5f);
            world.AddBody(plank2);

            // Spinning boxes (launched with off-center impulses)
            Box spinBox1 = new Box(new Vector2(5.0f, 7.0f), new Vector2(0.6f, 0.6f), 10f);
            spinBox1.BaseColor = Color.Beige;
            spinBox1.ApplyImpulseAtOffset(new Vector2(4.0f, -6.0f), new Vector2(0.3f, 0.0f));
            world.AddBody(spinBox1);

            Box spinBox2 = new Box(new Vector2(15.0f, 7.0f), new Vector2(0.6f, 0.6f), 10f);
            spinBox2.BaseColor = Color.Beige;
            spinBox2.ApplyImpulseAtOffset(new Vector2(-4.0f, -6.0f), new Vector2(-0.3f, 0.0f));
            world.AddBody(spinBox2);

            // Small fast circles
            Circle fast1 = new Circle(new Vector2(3.0f, 11.0f), 0.2f, 2f);
            fast1.BaseColor = Color.Yellow;
            fast1.Restitution = 0.8f;
            fast1.Friction = 0.2f;
            fast1.Velocity = new Vector2(8.0f, 1.0f);
            world.AddBody(fast1);

            Circle fast2 = new Circle(new Vector2(17.0f, 11.0f), 0.2f, 2f);
            fast2.BaseColor = Color.Yellow;
            fast2.Restitution = 0.8f;
            fast2.Friction = 0.2f;
            fast2.Velocity = new Vector2(-8.0f, 1.0f);
            world.AddBody(fast2);

            // High-drag objects that still move initially
            Box dragBox = new Box(new Vector2(10.0f, 9.0f), new Vector2(0.8f, 0.8f), 15f);
            dragBox.BaseColor = Color.Violet;
            dragBox.DragCoefficient = 2.0f;
            dragBox.Velocity = new Vector2(3.0f, -2.0f);
            dragBox.AngularVelocity = 2.0f;
            world.AddBody(dragBox);

            Circle dragCircle = new Circle(new Vector2(10.0f, 5.0f), 0.4f, 8f);
            dragCircle.BaseColor = Color.Pink;
            dragCircle.DragCoefficient = 1.5f;
            dragCircle.Velocity = new Vector2(-2.0f, 3.0f);
            world.AddBody(dragCircle);

            // A few more random objects to fill the space
            Circle extra1 = new Circle(new Vector2(1.5f, 5.0f), 0.35f, 12f);
            extra1.BaseColor = Color.Lime;
            extra1.Restitution = 0.7f;
            extra1.Velocity = new Vector2(5.0f, -3.0f);
            extra1.AngularVelocity = 8.0f;
            world.AddBody(extra1);

            Circle extra2 = new Circle(new Vector2(18.5f, 5.0f), 0.35f, 12f);
            extra2.BaseColor = Color.Lime;
            extra2.Restitution = 0.7f;
            extra2.Velocity = new Vector2(-5.0f, -3.0f);
            extra2.AngularVelocity = -8.0f;
            world.AddBody(extra2);

            Box extraBox = new Box(new Vector2(10.0f, 1.0f), new Vector2(1.2f, 0.6f), 25f);
            extraBox.BaseColor = Color.SkyBlue;
            extraBox.Velocity = new Vector2(0.5f, -2.0f);
            world.AddBody(extraBox);
        }
    }
}