Newbie help with Lerp (vector) + Timeline for smooth moving actors

Development Programming & Scripting
1

Hi! I’m really new to UE4, so probably just making a simple mistake. I have researched other questions asking similar stuff and I saw Lerp + Timeline being mentioned for this simple task. I’m trying to use Lerp and Timeline to move an actor from one location to another (from a Cube to a Sphere).

First I try to set the location of the object (a custom blueprint class called InformationLightBlueprint) to the Cube, which works just fine. Then I wait for 5 seconds and run the Lerp + Timeline combo to try to move my InformationLightBlueprint actor to the Sphere. However, when I click Play, I see the flow of the program through Blueprint and all looks well from that view. However, in the viewport nothing exciting happens - the initial SetActorLocation sets the object inside the Cube (what I want), but it’s never moved to the Sphere…

Here is my BluePrint:

52701-lerp-move.png
52701-lerp-move.png1640×876 227 KB

And here is my Timeline Template:

52702-lerp-timeline.png
52702-lerp-timeline.png1788×827 89.6 KB

And here is my main Viewport view in case that’s also helpful:

52703-lerp-viewport.jpg
52703-lerp-viewport.jpg1859×888 234 KB

Any idea what might be the problem here? I’ve spent a lot of time looking at other answers and I just can’t seem to figure it out.

As a more general question, I’m at a bit of a loss of how to debug stuff in general in UE4. I’ve run into this issue a few times where I see the Blueprint flow apparently working just fine, but nothing happens in the Viewport associated with it. I’m a programmer and totally new to UE4, my normal technique of adding print statements/looking for exceptions doesn’t seem to work here… any tips or tricks?

2

Hi,

i’m not an expert in animation, but to clarify basic things i want you tell next:

lerp actually is Linear interpolation Linear interpolation - Wikipedia, it can be used to move one object to another with proportional speed depending on distance, for example

if you move A object to B and distance increases you can calculate acceleration for A using lerp, don’t know if this somehow can affect smoothnes in animation, it’s more about rendering, then moving, but if your problem exactly that you B get’s moved and A doesn’t accelerate, then it’s algorythm problem and you have to PRINT your ALPHA value

to clarify things even more here’s simple example of calculation between 3 numbers

Lerp(100, 200, 0)=100
Lerp(100, 200, 1)=200
Lerp(100, 200, 0.5)=150
Lerp(100, 200, 0.25)=125

3

Gah, OK I figured it out. My InformationLightBlueprint Default Scene Root was set to “static” when it should have been set to “movable”.

To answer my other question about debugging, it helps a lot to have the logging console set. I saw a bunch of warnings about the InformationLightBlueprint being set to static and that led me in the right direction. I also saw a “Blueprint debugger” option somewhere in there and will probably check that out too. There is also the tried and true add a bunch of print statements and watch your output option that helped me out some as well.

4

thanks for the clarification!