koobas.hobune.stream
Why is .Lerp so bumpy?
I am trying to make my own gun script and for some reason my gun is acting super bumpy. My script is:
public Transform gunHolder;
public float holdSide = 0.3f;
public float holdHeight = -0.2f;
public float moveSpeed = 1;
public float rotateSpeed = 1;
void Start ()
{
}
void Update ()
{
gunHolder.localPosition = new Vector3(holdSide, holdHeight, 0);
transform.position = Vector3.Lerp(transform.position, gunHolder.position, moveSpeed);
transform.rotation = Quaternion.Lerp(transform.rotation, gunHolder.rotation, moveSpeed);
}
Does anyone know a better way of doing this? Thanks.
It could be partly due to different frame durations. You can test that by adding a random-length delay to your Update function and observing how well your game deals with it.
To compensate for that, for the last parameter to either Lerp function, pass:
1 - Mathf.Exp(-k * Time.deltaTime)
Here 'k' is a constant that controls the lerp rate.
Some people use a multiple of Time.deltaTime as the third parameter here, but that is wrong for Lerp - you should use an exponential of the form I stated above, to properly correct for varying frame times.
Beyond that, if the target object is moving with a fairly constant speed then you'll still get some jitter, and can do even better with an alternate lerp function. See this thread for more details:
and the webplayer demo I uploaded here (the bottom cube uses my custom lerp function):
http://www.gfootweb.webspace.virginmedia.com/SmoothDamp/WebPlayer.html
moveSpeed = 1 means you jump in one frame without smoothing. Try 0.1f for starters and play around with it till it feels right
The third parameter should be a number between 0 and 1.
If you imaging a line going from the first parameter to the second parameter, the third parameter represents percentage of progress along than line that is used for the return value.
Here is a table that may help visualise the concept.
first second third return 10 20 0.00 10 10 20 0.25 12.5 10 20 0.50 15 10 20 0.75 17.5 10 20 1.00 20For a lerp to look smooth and even it should a stable start and end values with a "`t`" value that ranges between 0 and 1.
To take your postion lerp as an example:
The start value (`transform.position`) is changing as it is updated every time.
The end value (`gunHolder.position`) may be changing (player input?).
The "`t`" value is fixed.
This would mean that you would be move a fixed percentage closer to the end value on each frame.
This is an example with a "`t`" of 0.5 (to make the maths easier I am treating start & end as stable) :
frame# first second third return delta 1 10 20 0.5 15 5 2 10 20 0.5 17.5 2.5 3 10 20 0.5 18.75 1.25 4 10 20 0.5 19.375 0.625As you can see the rate of movement (delta) starts high but quickly tends towards zero. For this use of lerp the trick to to find a "`t`" value that is not too high and not too low, it involves manual tweaking and a judjment call.
