• Products
  • Solutions
  • Made with Unity
  • Learning
  • Support & Services
  • Community
  • Asset Store
  • Get Unity

UNITY ACCOUNT

You need a Unity Account to shop in the Online and Asset Stores, participate in the Unity Community and manage your license portfolio. Login Create account
  • Blog
  • Forums
  • Answers
  • Evangelists
  • User Groups
  • Beta Program
  • Advisory Panel

Navigation

  • Home
  • Products
  • Solutions
  • Made with Unity
  • Learning
  • Support & Services
  • Community
    • Blog
    • Forums
    • Answers
    • Evangelists
    • User Groups
    • Beta Program
    • Advisory Panel

Unity account

You need a Unity Account to shop in the Online and Asset Stores, participate in the Unity Community and manage your license portfolio. Login Create account

Language

  • Chinese
  • Spanish
  • Japanese
  • Korean
  • Portuguese
  • Ask a question
  • Spaces
    • Default
    • Help Room
    • META
    • Moderators
    • Topics
    • Questions
    • Users
    • Badges
  • Home /
avatar image
0
Question by SamueleSaviano · Feb 22, 2021 at 01:49 PM · c#physics2dcar gamecar physics

2D Car Physics for Drag Race Game

Hello there!

I'm trying to develop a 2D drag race game so I need to code a simple but (almost) realistic physics system for the car. In a drag race the car just needs to go straight forward as fast as it can, so I don't need to handle braking or curves.

I'm following this tutorial and it helped me a lot: https://asawicki.info/Mirror/Car%20Physics%20for%20Games/Car%20Physics%20for%20Games.html

I already wrote some code and it seems to work properly as long as I don't change gear. In fact as soon as I insert the 2nd gear, acceleration becomes negative and so the car slows down, so I'm basically trying to understand what I did wrong.

This is the code I wrote so far and my torque curve. Thank you to anyone who will help me a bit with this!

alt text

 [RequireComponent(typeof(Rigidbody2D))]
 public class CarController : MonoBehaviour
 {
     #region CONSTANTS
 
     private const float c_friction = 0.3f;
     private const float c_frontalArea = 2.2f;
     private const float c_airDensity = 1.9f;
     private const float c_efficiency = 0.7f;
 
     #endregion
 
     #region PRIVATE
 
     private Rigidbody2D _rb;
 
     private Vector2 _velocity;
     private Vector2 _lastVelocity;
 
     private Vector2 _position;
     private Vector2 _lastPosition;
 
     private Vector2 _direction => this.transform.right;
     private Vector2 _traction => this._direction * this._driveForce;
     private Vector2 _drag => -this._dragCoef * this._velocity * this._velocity.magnitude;
     private Vector2 _rolling => -this._rollingCoef * this._velocity;
     private Vector2 _logitude => this._traction + this._drag + this._rolling;
     private Vector2 _driveForce => this._direction * this.TorqueAtRpm(this._rpm) * this.GearMultiplier() * CarController.c_efficiency / this.wheelRadius;
     private Vector2 _acceleration => this._logitude / this.mass;
 
     private float _dragCoef => 0.5f * CarController.c_friction * CarController.c_frontalArea * CarController.c_airDensity * this._speed;
     private float _rollingCoef => 30f * this._dragCoef;
     private float _wheelRotationRate => this._velocity.x / this.wheelRadius;
     private float _wheelAcceleration => this.TorqueAtRpm(this._rpm) * this.GearMultiplier() * CarController.c_efficiency;
 
     private float _rpm;
     private float _speed;
 
     private int _currentGear = 1;
 
     #endregion
 
     #region GETTERS
 
     private float GearRatio(int p_gear = 0)
     {
         return this.gearRatios[p_gear == 0 ? this._currentGear : p_gear - 1];
     }
 
     private float GearMultiplier(int p_gear = 0)
     {
         return this.GearRatio(p_gear) * this.differentialRatio;
     }
 
     private float TorqueAtRpm(float p_rpm)
     {
         return this.torqueCurve.Evaluate(p_rpm);
     }
 
     #endregion
 
     public AnimationCurve torqueCurve;
 
     [Space]
 
     public float minRPM; //700
     public float maxRPM; //8000
 
     [Space]
 
     public float mass; //1465 (kg)
     public float wheelRadius; //0.34 (m)
 
     [Space]
 
     public float[] gearRatios; //{ 3.08, 2.19, 1.63, 1.29, 1.03, 0.84, 0.69 }
     public float differentialRatio; //4.37
 
     private void Awake()
     {
         this._rb = this.GetComponent<Rigidbody2D>();
     }
 
     private void Update()
     {
         if (Input.GetKeyDown(KeyCode.UpArrow))
         {
             if (this._currentGear < this.gearRatios.Length - 1)
             {
                 this._currentGear++;
             }
         }
     }
 
     private void FixedUpdate()
     {
         this._velocity = this._lastVelocity + Time.fixedDeltaTime * this._acceleration;
 
         if(this._lastVelocity != this._velocity)
         {
             this._lastVelocity = this._velocity;
         }
 
         this._position = this._lastPosition + Time.fixedDeltaTime * this._velocity;
 
         if(this._lastPosition != this._position)
         {
             this._lastPosition = this._position;
         }
 
         this.GetRPM();
 
         this._rb.AddForce(this._driveForce, ForceMode2D.Force);
 
         this._speed = Mathf.Sqrt(Mathf.Pow(this._velocity.x, 2) + Mathf.Pow(this._velocity.y, 2)) * 3.6f;
     }
 
     private void GetRPM()
     {
         this._rpm = this._wheelRotationRate * this.GearMultiplier() * 60f / Mathf.PI;
 
         if (this._rpm < this.minRPM)
         {
             this._rpm = this.minRPM;
         }
 
         if(this._rpm > this.maxRPM)
         {
             this._rpm = this.maxRPM;
         }
     }
 
 }


curve.png (28.9 kB)
Comment
Add comment · Show 1
10 |3000 characters needed characters left characters exceeded
▼
  • Viewable by all users
  • Viewable by moderators
  • Viewable by moderators and the original poster
  • Advanced visibility
Viewable by all users
avatar image MeButFrustrated · 4 days ago 0
Share

Hi, I have a similar problem, do you think you could provide the program/code how you solved it? Thanks.

1 Reply

· Add your reply
  • Sort: 
avatar image
0

Answer by ChrisMercado · yesterday

I don't need any code. I just need some mathematical equations. Equations similar to these: If my instantaneous acceleration, velocity and engine power is this much where should my car be located in the next tick? I just want some ideas on the algorithms/equations. I don't want a full fledged research. All I am hoping for is that anybody who already knows some equations and/or algorithms about a certain aspect of drag racing can let everyone know about that in an answer. I am hoping to make something out of the answers I receive. To begin, I have posted an answer to my own question.

TellTims.com

Comment
Add comment · Share
10 |3000 characters needed characters left characters exceeded
▼
  • Viewable by all users
  • Viewable by moderators
  • Viewable by moderators and the original poster
  • Advanced visibility
Viewable by all users

Your answer

Hint: You can notify a user about this post by typing @username

Up to 2 attachments (including images) can be used with a maximum of 524.3 kB each and 1.0 MB total.

Follow this Question

Answers Answers and Comments

696 People are following this question.

avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image avatar image

Related Questions

Accelerate and brake a car without wheel collider 1 Answer

Multiple Cars not working 1 Answer

Distribute terrain in zones 3 Answers

simple drift car movement 0 Answers

How to calculate angular velocity after a collision? 0 Answers


Enterprise
Social Q&A

Social
Subscribe on YouTube social-youtube Follow on LinkedIn social-linkedin Follow on Twitter social-twitter Follow on Facebook social-facebook Follow on Instagram social-instagram

Footer

  • Purchase
    • Products
    • Subscription
    • Asset Store
    • Unity Gear
    • Resellers
  • Education
    • Students
    • Educators
    • Certification
    • Learn
    • Center of Excellence
  • Download
    • Unity
    • Beta Program
  • Unity Labs
    • Labs
    • Publications
  • Resources
    • Learn platform
    • Community
    • Documentation
    • Unity QA
    • FAQ
    • Services Status
    • Connect
  • About Unity
    • About Us
    • Blog
    • Events
    • Careers
    • Contact
    • Press
    • Partners
    • Affiliates
    • Security
Copyright © 2020 Unity Technologies
  • Legal
  • Privacy Policy
  • Cookies
  • Do Not Sell My Personal Information
  • Cookies Settings
"Unity", Unity logos, and other Unity trademarks are trademarks or registered trademarks of Unity Technologies or its affiliates in the U.S. and elsewhere (more info here). Other names or brands are trademarks of their respective owners.
  • Anonymous
  • Sign in
  • Create
  • Ask a question
  • Spaces
  • Default
  • Help Room
  • META
  • Moderators
  • Explore
  • Topics
  • Questions
  • Users
  • Badges