How to scale an object to a certain size over a certain period of time(in seconds lets say)

Question

So i've been trying to figure out what equation i need to use to be able to achieve what is mentioned in the post title. first i tried something like:

 gameObject.transform.localScale  += (new Vector3(0.1f, 0f, 0.1f) * (-gameObject.transform.localScale.x * Time.deltaTime))/10;

which didnt work. I then tried:

 gameObject.transform.localScale = Vector3.Lerp (transform.localScale, new Vector3(5f,5f,5f), 10f * Time.deltaTime);

which also didnt quite work :( can anyone tell me what im missing?

Answer 1

Answer by Eno-Khaon · Sep 18, 2021 at 04:00 AM

Using Time.deltaTime as part of the "time" (namely, "t") argument in Linear Interpolation is almost always a terrible idea, and I never understand why it's done so frequently. Essentially, it removes the "Linear" element and makes it state/luck-dependent on exactly how it plays out without being able to reach its goal.

If you want an "animated" Lerp() function to play out, well, linearly, you'll want a fixed start and end point, with a "t" value that ranges from 0-1 over a given length of time.

 // This example is based around multiplication for more efficient math
 private float fScaleTime;
 public float scaleTime
 {
     get
     {
         if(fScaleTime == 0f)
         {
             return 0f;
         }
         else
         {
             return 1.0f / fScaleTime;
         }
     }
     set
     {
         if(value == 0f)
         {
             fScaleTime = 0f;
         }
         else
         {
             fScaleTime = 1.0f / value;
         }
     }
 }
 
 // An editor-facing initial value, since the property would be hidden in the Inspector
 [SerializeField]
 private float initialScaleTime = 5.0f;

 public Vector3 startingScale = Vector3.one * 0.1f;
 public Vector3 endingScale = Vector3.one * 5.0f;
 
 private float lerpT = 0f;
 
 void Start()
 {
     // Set the property to the Inspector value
     scaleTime = initialScaleTime;
     // Redundant in Start() in this case, but included for general context
     lerpT = 0f;
 }
 
 void Update()
 {
     // Simple example, no conditions involved for this
     transform.localScale = Vector3.Lerp(startingScale, endingScale, lerpT * fScaleTime);
     lerpT += Time.deltaTime;
 }

^{Edit: Fixed an obvious typo}

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aLovedHater · Sep 18, 2021 at 09:30 PM 0

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I haven't used get/set in a long time in C# and i happen to get some errors im a little confused about. my full code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Zone : MonoBehaviour
 {
     ZoneStuff zoneStuff;
     bool canReplace = true;
 
     // An editor-facing initial value, since the property would be hidden in the Inspector
     [SerializeField]
     private float initialScaleTime = 5.0f;
     public Vector3 startingScale = Vector3.one * 0.1f;
     public Vector3 endingScale = Vector3.one * 5.0f;
     
     private float lerpT = 0f;
 
     private float fScaleTime;
     public float scaleTime
     {
         get
         {
             if(fScaleTime == 0f)
             {
                 return 0f;
             }
             else
             {
                 return 1.0f / fScaleTime;
             {
         }
         set
         {
             if(value == 0f)
             {
                 fScaleTime = 0f;
             }
             else
             {
                 fScaleTime = 1.0f / value;
             }
         }
     }
 
     void Awake()
     {
         zoneStuff = GameObject.Find("GameManager").GetComponent<ZoneStuff>();
     }
     
     // Start is called before the first frame update
     void Start()
     {
         // Set the property to the Inspector value
         scaleTime = initialScaleTime;
         // Redundant in Start() in this case, but included for general context
         lerpT = 0f;
     }
 
     // Update is called once per frame
     void Update()
     {
          // Simple example, no conditions involved for this
         transform.localScale = Vector3.Lerp(startingScale, endingScale, lerpT * fScaleTime);
         lerpT += Time.deltaTime;
     }
     
     void OnTriggerEnter(Collider other)
     {
         if(other.gameObject.tag == "Zone")
         {
             if(canReplace)
             {
                 canReplace = false;
                 zoneStuff.ReplaceZone(this.gameObject);
             }
         }
     }
 }

errors: line 32, CS1002: ; expected line 45, CS1513: } expected

Eno-Khaon aLovedHater · Sep 21, 2021 at 06:28 PM 0

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Whoops, I made a typo, and put a second starting brace ({) where there should have been an ending brace (}).

This is a pretty good reason to not blindly copy/paste code.

How to scale an object to a certain size over a certain period of time(in seconds lets say)

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