wrplat-godot/src/components/PlayerPhysicsController.cs

using Godot;
using System;
using System.Diagnostics;

public partial class PlayerPhysicsController : CharacterBody2D {
    [Export]
    public float FloatingWalkAcceleration { get; set; } = 1f;
    [Export]
    public float RunMultiplier { get; set; } = 1.84f;
    [Export]
    public float WalkAcceleration { get; set; } = 3f;

    [Export]
    public float JumpHeight { get; set; } = 5.5f;

    private float PeakTime { get; set; } = 0.1f;

    [Export]
    public float DragArea { get; set; } = 4f;

    [Export]
    public float AirDensity { get; set; } = 37.26982f;

    [Export]
    public float DragCoefficient { get; set; } = 1.3f;
    [Export]
    public float FloatingDragCoefficientMultiplier { get; set; } = 0.8f;

    [Export]
    public Label DebugTextLabel { get; set; }

    [Export]
    public AnimatedSprite2D Sprite { get; set; }

    [Export]
    public float Gravity { get; set; } = 30.625f;

    private float TilesToMeters => 9.81f / Gravity;

    private float PxToMeters => (1 / UnitToPx) * TilesToMeters;

    [Export]
    public float UnitToPx { get; set; } = 32;

    private float _lv = 0.0f;
    private float _invmass = 1/2f;
    [Export]
    public float Mass { get => 1/_invmass; set => _invmass = 1/value; }

    private float epsilon = 10e-5f;

    private void RecalculateLv() {
        _lv = Mathf.Sqrt(Mathf.Pow(Gravity * PeakTime / 2, 2) + 2 * Gravity * JumpHeight);
    }

    private float CalculateDrag(float velocity, float delta) {
        var minopposing = Mathf.Abs(velocity * 0.99f);
        return Mathf.Clamp(
            0.5f * 
            (this.IsOnFloor() ? DragCoefficient : DragCoefficient * FloatingDragCoefficientMultiplier) * 
            (Mathf.Pow(TilesToMeters, 3) * AirDensity) * 
            (Mathf.Pow(TilesToMeters, 2) * DragArea) * 
            Mathf.Pow(velocity * PxToMeters, 2) * 
            _invmass * 
            -Mathf.Sign(velocity) *
            delta *
            (1f / TilesToMeters),
            -minopposing,
            minopposing);
    }

    public override void _Ready() {
        RecalculateLv();
        base._Ready();
    }

    
    public override void _Process(double delta) {
        var grounded = this.IsOnFloor();
        var absvel = new Vector2(Mathf.Abs(Velocity.X), Mathf.Abs(Velocity.Y));
        Sprite.FlipH = Velocity.X < 0;
        if (grounded && absvel.X > 0) {
            Sprite.Play("walk", absvel.X switch {
                < 10 => 1,
                < 150 => 2,
                < 300 => 4,
                _ => 1
            });
        } else if (grounded && absvel.X < epsilon && absvel.Y < epsilon) {
            Sprite.Play("idle");
        }
    }

    private float _timeOffGround = 0.0f;

    [Export]
    public float CoyoteTiming { get; set; } = 0.1f;


    public override void _PhysicsProcess(double delta) {
        var xAxis = Input.GetAxis("move_left", "move_right");
        var yAxis = Input.GetAxis("look_up", "look_down");
        // var jumpStrength = -Input.GetActionStrength("jump");

        var lastCollision = this.IsOnCeiling();
        RecalculateLv();

        float velx = (Velocity.X / UnitToPx) + CalculateDrag(Velocity.X, (float)delta);
        float vely = (Velocity.Y / UnitToPx) + Gravity * (float)delta + CalculateDrag(Velocity.Y, (float)delta);

        if (Mathf.Abs(velx) < 0.3) velx = 0;

        var grounded = this.IsOnFloor();
        var coyoteGrounded = _timeOffGround < CoyoteTiming;
        if (grounded || coyoteGrounded) {
            if (grounded) _timeOffGround = 0;
            else _timeOffGround += (float)delta;

            if (Input.IsActionJustPressed("jump")) {
                vely = -_lv;
            }

            if (!grounded && coyoteGrounded && Input.IsActionJustReleased("jump") && vely < 0) {
                vely *= 1/4f;
            }

            if (Input.IsActionPressed("run")) {
                velx += xAxis * WalkAcceleration * (float)delta * RunMultiplier;
            } else {
                velx += xAxis * WalkAcceleration * (float)delta;
            }
        } else {
            if (Input.IsActionJustReleased("jump") && vely < 0) {
                vely *= 1/4f;
            }

            if (Input.IsActionPressed("run")) {
                velx += xAxis * FloatingWalkAcceleration * (float)delta * RunMultiplier;
            } else {
                velx += xAxis * FloatingWalkAcceleration * (float)delta; 
            }
        }

        DebugTextLabel.Text = 
            $"grounded: {grounded}\n" + 
            $"vely: {vely}\n" +
            $"velx: {velx}\n" +
            $"lv  : {_lv:F2} or {_lv/(float)delta:F2}\n" +
            $"rd  : {CalculateDrag(Velocity.X, (float)delta):F2}, {CalculateDrag(Velocity.Y, (float)delta):F2}";
        // Force = new Vector2(0, forcey);
        Velocity = new Vector2(velx, vely) * UnitToPx;

        MoveAndSlide();
    }
}