MovementController.Integrated.cs

using System.Drawing;
using System.Numerics;
 
namespace Gondwana.Physics.Movement;

public sealed partial class MovementController
{
    public void SetVelocity(Vector2 velocity)
    {
        CancelScript();
        _state.Velocity = velocity;
    }

    public void SetAcceleration(Vector2 acceleration)
    {
        CancelScript();
        _state.Acceleration = acceleration;
    }

    public void SetMaxSpeed(float? maxSpeed)
    {
        _state.MaxSpeed = maxSpeed;
    }

    public void SetLinearDamping(float dampingPerSec)
    {
        _state.LinearDamping = MathF.Max(0f, dampingPerSec);
    }
 
    private bool AdvanceIntegrated(float dt)
    {
        if (_state.HasMotion)
        {
            Step(dt);       // physics (accel/vel/damping/wrap/space-convert)
            return true;
        }
 
        return false;
    }

    private void Step(float dt)
    {
        // integrate kinematics in the mover's own space
        _state.Velocity += _state.Acceleration * dt;
        ClampVelocity();
 
        // exponential damping (frame-rate independent)
        if (_state.LinearDamping > 0f)
            _state.Velocity *= MathF.Exp(-_state.LinearDamping * dt);
 
        // kill tiny velocities when no accel
        const float StopEpsilon = 0.01f;
        if (_state.Acceleration == Vector2.Zero &&
            _state.Velocity.LengthSquared() < StopEpsilon * StopEpsilon)
            _state.Velocity = Vector2.Zero;
 
        // move in the mover's space
        var pos = _mover.GetPosition();
        var newPos = pos + _state.Velocity * dt;
 
        // optional wrapping if mover lives in Grid space
        if (_mover.PositionSpace == MovementSpace.Grid && (WrapX || WrapY))
        {
            if (_coords is null || _sceneLayer is null)
                throw new InvalidOperationException("Grid wrapping requires coordinates/layer.");
 
            var wrapped = _coords.FindEquivalentSceneLayerCoordinates(
                new PointF(newPos.X, newPos.Y),
                _sceneLayer.GridColumnCount - 1, _sceneLayer.GridRowCount - 1);
 
            float newX = newPos.X;
            float newY = newPos.Y;
 
            if (WrapX)
                newX = wrapped.X;
 
            if (WrapY)
                newY = wrapped.Y;
 
            newPos = new Vector2(newX, newY);
        }
 
        _mover.SetPosition(newPos);
    }

    internal void ZeroVelocityComponent(bool zeroX, bool zeroY)
    {
        if (!zeroX && !zeroY)
            return;
 
        var v = _state.Velocity;
        _state.Velocity = new Vector2(zeroX ? 0f : v.X, zeroY ? 0f : v.Y);
    }

    private void ClampVelocity()
    {
        if (_state.MaxSpeed is null)
            return;
 
        var v = _state.Velocity;
        var speed = v.Length();
        var max = _state.MaxSpeed.Value;
 
        if (max > 0 && speed > max)
            _state.Velocity = v * (max / speed);
    }
}