Question by LPGaming-Company · Feb 12, 2013 at 12:38 AM · transform acceleration vehicle

Basic Acceleration Script

Trying to figure out how to get a basic acceleration script going for a car.

I have really slow internet so I can't download the Car Tutorial everyone recommends, but here is what I've got so far..

This works.. although it's kinda strange... it accelerates really slow for the first few seconds, then jumps to the max speed. Aswell as the car wont accelerate in 3rd gear+, it's stupid really. I don't see why.

 using UnityEngine;
 using System.Collections;
 
 public class MoveCar : MonoBehaviour {
     public float currSpeed;
     public float maxSpeed;
     
     public int currDamage;
     public int maxDamage;
     
     public int currRPM;
     public int redRPM;
     public int maxRPM;
     
     public int gear;
     public int maxGears;
     
     public float damagePerc;
     
     
     public bool reverse;
     public bool transAuto;
     
     // Use this for initialization
     void Start () {
         currSpeed=0f;
         maxSpeed=200f;
         currDamage=0;
         maxDamage=100;
         
         currRPM=0;
         redRPM=6150;
         maxRPM=7000;
         
         gear = 0;
         maxGears = 6;
         
         transAuto = true;
         reverse = false;
     }
     
     // Update is called once per frame
     void Update () {
         
         if(gear > 0 && (currRPM > redRPM) && transAuto) {
             gear++;
             currRPM-= (currRPM / 2);
         }
             
         
         switch(gear) {
             case 0: maxSpeed = 0; break;
             case 1: maxSpeed = 45; break;
             case 2: maxSpeed = 83; break;
             case 3: maxSpeed = 107; break;
             case 4: maxSpeed = 143; break;
             case 5: maxSpeed = 176; break;
             case 6: maxSpeed = 200; break;
         }
         if(Input.GetKeyUp(KeyCode.Q)) {
             if(gear < maxGears) {
                 gear++;
                 currRPM-= (currRPM / 2);
             }
         }
         
         if(Input.GetKeyUp(KeyCode.W)) {
             if(gear > 0) {
                 gear--;
                 currRPM+= (currRPM * 2);
             }
         }
         
         if(!reverse && currSpeed < 1) { currSpeed = 0; }
         if(reverse && currSpeed < -29) { currSpeed = -30; }
         
         if(Input.GetKey(KeyCode.UpArrow)) {
             if(currRPM < 0) currRPM=0;
             if(currRPM < maxRPM) {
                 currRPM +=  8;
             }
             if(gear > 0) {
                 if(currSpeed < maxSpeed) {
                     currSpeed += ((.0004f * currRPM) / gear);
                 }
             }
         } else {
             currSpeed-= (int)((1 * gear) / 2);
             currRPM-= (int)(3 * Time.deltaTime);
         }
         
         if(Input.GetKey(KeyCode.DownArrow)) {
             reverse = true;
         } else {
             reverse = false;
         }
             
           transform.Translate(Vector3.forward * (currSpeed * Time.deltaTime) / 2);
             Debug.Log ("Speed: " +currSpeed+ " RPM: " +currRPM+ " Gear: " +gear);
     }
 }

0 Show 1

iwaldrop · Feb 12, 2013 at 04:39 AM 1

Hi. I got way into playing with your script. :)

Needless to say, there are quite a few things that still need to be worked out, like engine load for instance. But that's a pretty decent approximation of speed. You can change the gear rations and the tire dimensions to effect the simulation. Speed is in MPH, but the conversion to m/s is there; you just have to uncomment it. You're going to want to do that if you plan on simming anything in Unity, because Unity's world units are in meters.

 using UnityEngine;
 using System.Collections;
  
 public class MoveCar : MonoBehaviour
 {
     public float redlineRPM = 6150;
     public float maxRPM = 7000;
     private float maxDamage = 100;
     public float finalDrive;
     public float[] gearRatios;
     public TireDimensions tireDimensions;
     //public bool hasAutoTransmission = true;
     
     [HideInInspector] 
     public float damagePerc; //??
     
     private float tireCircumference;
     private float currentRPM;
     private float currentDamage;
     private float currentSpeed;
     private int currentGear;
     private bool reverse;
     
     void Awake()
     {
         tireCircumference = tireDimensions.Circumference / 12;
     }
  
     void Update()
     {
         bool changeUp = Input.GetKeyDown(KeyCode.Q);
         bool changeDown = Input.GetKeyDown(KeyCode.A);
         if (changeUp || changeDown)
             ChangeGear(changeUp);
         
         reverse = Input.GetKey(KeyCode.DownArrow);
         if(Input.GetKey(KeyCode.UpArrow))
         {
             if(currentRPM < maxRPM)
                   currentRPM += 10;
         }
         else
             currentRPM -= reverse ? 15 : 5;
         
         if (currentRPM < 0) currentRPM = 0;            // current RPM should never be 0 while the engine is running.
         
         // mph = (rpm * tireCircumfrence in feet) / (gear * final * 88) -- ref: http://www.type2.com/library/misc/calcspd.htm
         currentSpeed = ((currentRPM * tireCircumference) / (gearRatios[currentGear] * finalDrive * 88));// * 0.44704f;    // 1 mph = 0.44704 m/s
  
 #if UNITY_EDITOR
         Debug.Log(string.Format("Gear Ratio: {0}, Speed: {1}, RPM: {2}", gearRatios[currentGear], currentSpeed, currentRPM));
 #endif
         
         // move the object
         transform.Translate(Vector3.forward * Time.deltaTime);
     }
     
     void ChangeGear(bool changeUp)
     {
         if ((changeUp && currentGear < gearRatios.Length-1) || (!changeUp && currentGear > 0))
         {
             currentGear += (changeUp ? 1 : -1);
             //currentRPM *= (changeUp ? 0.5f : 2);
         }
     }
     
     [System.Serializable]
     public class TireDimensions
     {
         public float tireWidth = 215;
         public float sidewallHeightRatio = 45;
         public float wheelDiameter = 16;

     public float Circumference
             {
                     get { return (((tireWidth / 25.4f * sidewallHeightRatio/100 * 2) + wheelDiameter) * Mathf.PI); }
             }
     }
 }