Lerp Not Working Properly

[Liyang]

Hi! For some reason, my lerp isn’t working properly although I am sure I have not made any mistakes. It was always stuck around 45 and my target is 90.

Here is a function I wrote which combines both Open and Close.

My Tick and BeginPlay.

My H File. And lastly my Log

.

[DanM]

What is the initial yaw?

---

As an aside, “OpenAndClose” implies it’s going to do both at the same time. I think a better name would be OpenOrClose, or better yet IMO “RotateDoor”.

That function also 90% the same for both cases the one difference is the second argument. You could instead create a variable for that (also you’re missing the b prefix).

float ToYaw;
if (bDoorCose)
{
    ToYaw = InitialYaw;
}
else
{
    ToYaw = TargetYaw;
}
CurrentYaw = FMath::Lerp(CurrentYaw, ToYaw, ...);
// etc...

Or more succinctly use the ternary operator (aka conditional operator).

const float ToYaw = bCloseDoor ? InitialYaw : TargetYaw;
//                 ^-condition-^  ^if true   ^if false

[Liyang]

My InitialYaw is 0. And wow, your code is really clean! I will follow your advice, really makes my code easier to read, thanks! And FYI, the door isn’t always stuck at 45, it changes depending on what value I put in the Alpha parameter for the lerp function.

[DanM]

Are you sure, did you print out its value in BeginPlay?

[Liyang]

Yup, very sure. Just did so

[DanM]

And just to be sure, the TargetYaw? If that’s the expected value would you mind sending me your project using the following link?

https://gdev.tv/projectupload

Please use File > Package Project > Zip Up Project within Unreal as this will ensure only required files are zipped up and things like the Binaries are excluded.

[Liyang]

Alright, no problem, thanks. I submitted

[Liyang]

[DanM]

So what you sent works as expected. Only issue was that you didn’t call SetActorRotation.

float ToYaw;
if (bDoorClose)
{
	ToYaw = InitialYaw;
}
else
{
	ToYaw = TargetYaw;
}
CurrentYaw = FMath::Lerp(CurrentYaw, ToYaw, 0.2f * DeltaTime);
GetOwner()->SetActorRotation(FRotator(0.f, CurrentYaw, 0.f)); // This was missing

[Liyang]

Oops, I accidentally commented SetActorRotation out. I changed my code just like how you recommended, but I haven’t tried it out yet, as I have been busy, but now I did it works as expected. So the problem must lie within my old code. I went to have a look at my old code, the one I posted at the beginning, and recreated the code and found the mistake. I forgot to put else, so that causes my CurrentYaw to increase, and then to decrease again, my bad. Thanks and sorry for taking your time.