Why won't my object grow?

Questions & Answers
1

Hi, Im making a portal clone game and when I shoot my portal gun to place a portal on the wall I want the portal to gradually grow in size and then stop growing when it reaches the desired size. I figured I could do this with a lerp function but the portal does not grow for some reason (just appears small when I place it on the wall). I have no idea what Im doing wrong. Help!

using UnityEngine;
using System.Collections;

public class PortalShoot : MonoBehaviour {
	public GameObject leftPortal;
	public GameObject rightPortal;

	// Use this for initialization
	void Start () {

	}
	
	// Update is called once per frame
	void Update () {

		if (Input.GetMouseButtonDown (0)) {
			ShootPortal(leftPortal);
		}

		if (Input.GetMouseButtonDown (1)) {
			ShootPortal(rightPortal);
		}
	}

	void ShootPortal(GameObject portal){
		int x = Screen.width / 2;
		int y = Screen.height / 2;

		Ray ray = Camera.main.ScreenPointToRay (new Vector3 (x, y));
		RaycastHit hit;

		if(Physics.Raycast(ray, out hit) && hit.collider.tag != "Portal" && hit.collider.tag == "Wall"){
			portal.transform.position = hit.point;
			portal.transform.rotation = Quaternion.LookRotation(hit.normal);
			portal.transform.localScale = Vector3.Lerp(new Vector3(0.1f,0.1f,0.1f), new Vector3(2.5f,3.5f,0.01f), Time.deltaTime * 0.5f);

		}
	}
}
2

In general Lerp(from, to, t) = from*(1-t)+to*t

So for floats

Lerp(1, 2, 0) = 1*1+2*0 = 1+0=1, or from
Lerp(1, 2, 0.5) = 1*0.5+2*0.5 = 0.5+1=1.5 or halfway between from and to
Lerp(1, 2, 1.0) = 1*0+2*1 = 0+2=2, or to

In your example you are using

Vector3.Lerp(new Vector3(0.1f,0.1f,0.1f), new Vector3(2.5f,3.5f,0.01f), Time.deltaTime * 0.5f);

Let’s say your frames per second fluctuates around 25 to 100. Then Time.deltaTime will flucuate from 0.01 to 0.04. So the return of lerp will fluctuate between from0.99+to0.01 and from0.96+to0.04. Since your from and to are constants this means you portal will always remain close to the from sizes. In addition you only lerp once per click, when the portal is shot so the portal never resizes.

Two common ways to use Lerp are to have a changing t (third variable) or a changing from (first variable). For instance

float time;
void Update()
{
     if (Input.GetMouseButtonDown (0)) {
          time=0;
     }

     time+=Time.deltaTime;
     Debug.Log(Mathf.Lerp(1, 2, time));
}

and

float from;
void Update()
{
     if (Input.GetMouseButtonDown (0)) {
          from=1;
     }

     from=Mathf.Lerp(from, 2, Time.deltaTime);    
     Debug.Log(from);
}

Personally I stick to changing t (third variable) as, to me, it feels like if you’re changing from (first variable) then you shouldn’t be using lerp in the first place but rather another function like a polynomial, exponential, or sin.