78 lines
3.0 KiB
C#
78 lines
3.0 KiB
C#
using System;
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using System.Numerics;
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using Raylib_cs;
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namespace PhysicsEngine
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{
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public class Box : Body
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{
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public Vector2 Size;
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public Box(Vector2 position, Vector2 size, float mass)
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{
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Position = position;
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Size = size;
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Mass = mass;
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MomentOfInertia = (1.0f / 12.0f) * mass * (size.X * size.X + size.Y * size.Y);
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}
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public override void Draw(float pixelsPerMeter = 100.0f)
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{
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DrawHelper.DrawRotatedBox(Position, Size, Rotation, BaseColor, pixelsPerMeter);
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}
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private Vector2 RotatePoint(Vector2 point, float radians)
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{
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float cos = MathF.Cos(radians);
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float sin = MathF.Sin(radians);
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return new Vector2(
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point.X * cos - point.Y * sin,
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point.X * sin + point.Y * cos
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);
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}
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public override void ApplyAerodynamicDrag(float dt)
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{
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if (DragCoefficient <= 0.0f) return;
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const float airDensity = 1.225f;
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float speed = Velocity.Length();
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if (speed < 0.01f) return;
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// 1. Oncoming relative wind direction (opposite to velocity)
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Vector2 windDir = -Velocity / speed;
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float cos = MathF.Cos(Rotation);
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float sin = MathF.Sin(Rotation);
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// Box local axes transformed into world space (Assuming Size.Y is length/major axis)
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Vector2 worldAxisY = new Vector2(-sin, cos); // Major axis vector
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Vector2 worldAxisX = new Vector2(cos, sin); // Minor axis vector
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// 2. Calculate effective frontal width (projected area in 2D) based on current orientation
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Vector2 windPerp = new Vector2(-windDir.Y, windDir.X);
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float projX = MathF.Abs(Vector2.Dot(worldAxisX, windPerp));
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float projY = MathF.Abs(Vector2.Dot(worldAxisY, windPerp));
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float effectiveWidth = Size.X * projX + Size.Y * projY;
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// 3. Translational Drag Force (scales with dynamic pressure and current effective width)
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float dragMagnitude = 0.5f * airDensity * speed * speed * DragCoefficient * effectiveWidth;
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Vector2 dragForce = windDir * dragMagnitude;
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ApplyForce(dragForce);
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// 4. Weathercock / Fin-Effect Restoring Torque
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// Measures angular misalignment between the box's major axis and the wind direction
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float cross = worldAxisY.X * windDir.Y - worldAxisY.Y * windDir.X;
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float restoringTorque = cross * 0.5f * airDensity * speed * speed * DragCoefficient * Size.X * Size.Y;
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ApplyTorque(restoringTorque);
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// 5. Angular Damping (Quadratic Rotational Drag)
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float angularSpeed = MathF.Abs(AngularVelocity);
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if (angularSpeed > 0.0001f)
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{
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float angularDragTorque = -MathF.Sign(AngularVelocity) * 0.5f * airDensity * angularSpeed * angularSpeed * DragCoefficient * (Size.X + Size.Y);
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ApplyTorque(angularDragTorque);
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}
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}
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}
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} |