Mathf.Lerp Question

Questions & Answers
1

Hi, a really noob question, i got this code from the unity manual

// Fades from minimum to maximum in one second

var minimum = 10.0;
var maximum = 20.0;

function Update () {
transform.position = Vector3(Mathf.Lerp(minimum, maximum, Time.time), 0, 0);
}

Now how would u make it instead of one second say 3 or 4? I tried Time.deltaTime * 4 but the results are weird.

EDITED: My goal is to move a gun (FPS) to the center of the screen when we zoom in roughly at the same speed as the cam FOV decreases then return it to the original position.

I have this code so far:

function LateUpdate () {
  if (Input.GetButtonDown ("Fire2")){ 
    pressing = true; 
  } 
  if (Input.GetButtonUp ("Fire2")){ 
    pressing = false; 
  } 
  // Calculate the desired distance 
  if (pressing){ 
    camera1.fieldOfView = Mathf.Lerp(camera1.fieldOfView, zoomFOV, Time.deltaTime * lerpSpeed);
    gun.localPosition = Vector3(Mathf.Lerp(minimum, maximum, Time.time ), -0.2390689, 0.4984837);
    DOF.enabled = true;
  } 
  else 
  if (!pressing) { 
    camera1.fieldOfView = Mathf.Lerp(camera1.fieldOfView, normalFOV, Time.deltaTime * lerpSpeed);

    gun.localPosition = Vector3(Mathf.Lerp(maximum, minimum, Time.time ), -0.2390689, 0.4984837); 
    DOF.enabled = false; 
  }
2

This is a bad example, because it uses Time.time - it starts counting when the game begins, and never returns to zero, so you will only see this working once. It’s better to do something like this:

var minimum = 10.0; 
var maximum = 20.0;
var duration: float = 4; // duration in seconds
var timer: float = 0;    // set this to zero to repeat the cycle

function Update () { 

    transform.position = Vector3(Mathf.Lerp(minimum, maximum, timer), 0, 0); 
    timer += Time.deltaTime/time; // add time elapsed since last Update
}

EDITED: You can do that in a simpler manner. Since Mathf.Lerp(from, to, t) returns a value between from and to proportional to t, you can increment t from 0 to 1 when Fire2 is pressed, and return to 0 when it’s released. This can be done by adding or subtracting Time.deltaTime/duration from the variable t. The variable t is clamped between 0 and 1, so when you press or release Fire2 t always take the same time to go or return.

var t: float = 0;
var duration: float = 3;

function LateUpdate () {
  if (Input.GetButton("Fire2")){ // if fire2 pressed...
    DOF.enabled = true; // enable DOF
    t += Time.deltaTime/duration; // t goes towards 1
  }
  else { // if fire2 not pressed...
    DOF.enabled = false; // disable DOF
    t -= Time.deltaTime/duration; // t goes towards 0
  }
  t = Mathf.Clamp(t, 0, 1); // keep t between 0 and 1
  camera1.fieldOfView = Mathf.Lerp(normalFOV, zoomFOV, t);
  gun.localPosition.x = Mathf.Lerp(minimum, maximum, t);
}
3

I do it this simple way…

float temp;
bool lerpStarted;
float noOfSeconds;

void callThisToStartLerp()
{
temp = Time.time;
lerpStarted = true;
}

void Update()
{
if(lerpStarted)
{
transform.position = Vector3(Mathf.Lerp(minimum, maximum, (Time.time - temp)/noOfSeconds), 0, 0);
}
}

In this Way, You can use lerp for any no. of seconds defined in noOfSeconds.
and you can use yield to false the bool var lerpStarted.