Weird rotations along spline

Development Programming & Scripting
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1

Hi!

I am trying to create a simple project where a train follows a spline, easy. Everything is working, but at some points, the train is rotating up and down really fast for no obvious reason. I checked spline points, there are no sharp curves or something like that.
I also dynamically spawn railroad mesh along the same spline and there are no weird rotations or curves.

Here is a video demonstration:
https://youtu.be/CTOWvyNvMBU

Here is how my railroad looks at that location where weird rotations happen:

spline
spline1510Ă—867 106 KB

Also, here is my blueprint code:
Spline location and rotation logic posted by anonymous | blueprintUE | PasteBin For Unreal Engine

This method is called from Tick event

I would really appreciate any help because I am struggling with this for days.

Thanks!

2

I think it’s possibly this construct

image
image907Ă—680 101 KB

If you want the train to be further along the spline, you have to just add to the Distance variable

image
image1019Ă—359 41 KB

you can’t add a vector afterwards :slight_smile:

Even if it’s just the height of the car, I don’t think adding a constant will work, because it’s not taking spline rotation into account.

3

Hi, thanks for the answer!

This offset is actually for Z axis, I want the train to be offset from the rail actually and this does not change in runtime at all.

Also tried without the offset, and the same thing happens :confused:

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4

Ok, so not that then :slight_smile:

I was just saying, that if the spline is twisting, then Z needs to be relative to the spline. It’s not just up.

Is the spline smooth? Maybe it’s just bumps in the spline.

5

Yup, I agree with you. I do not plan to have any twists on the spline but I should keep that in mind.

Regarding the spline itself, it is just a straight line:

train
train1519Ă—881 104 KB

Also, I have a bridge in front of this image, and rails (spline) is curving upwards (elevating) and the train does not glitch there at all. Also, there is a long straight rail section, nothing happens there.

Btw, since I am new to Unreal, here is how I configured my Train actor, in case I misconfigured something:
image

Train Static mesh is the mesh you see, Speed Lever static mesh is just a mesh inside the train that you can use to start/stop the train, and the Trigger box is just that, it does not collide with anything.

6

Another thing I noticed, and this is really weird for me.
I tried printing train’s actor rotation every frame, and pitch rotation ranges from 0.1 to 0.3, but at the moment when the train “jumps”, it goes to around 2.5:

image
image423Ă—860 102 KB

Isn’t this just 2 degrees? I guess I wouldn’t even notice rotation this small, right?

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7

Could be. A couple of degrees is very noticeable when you’re riding on top of it, I think :slight_smile:

EDIT: You can’t cut the pitch out, by why are there these little variations, I wonder…?

8

No idea. I just deleted two points I had there and those bumps do not happen anymore, but I still have no idea what could be the cause.

Anyways, I really appreciate your help, thank you!

1 Like