5.7.3 Bug, PCG Spline Sampler

Bug introduced in 5.7.3.
Was not bugged in 5.7.2 and never before.

Setup

Results

Expected/Previous/Correct behavior

Core problem

Sampled point:

  • Position: Point position
  • Rotation: From X axis going to next point
  • Bounds Y & Z: [-1; 1]
  • Bounds X before: [half negative Distance to previous point; half Distance to next point]
  • :warning: Bounds X now: [half negative Distance to previous point; 1] :warning:

Main issue now:
Point N is oriented toward Point N+1 but we only have the distance toward Point N-1

Priority

Critical for us.
Our game world is build out of PCG, we are near end of production.
Now we can’t edit our maps.
We can’t downgrade to 5.6.
Minor hotfix version (5.7.2) are not available without recompiling the engine?

Solution

I don’t have any proper solution.

Hotfix (dirty just adapted to our situation):

The issue of abnormal interior point sampling on PCG Splines is still present in UE 5.7.4.

Hi! Very sorry to only see it now.
It seems a bad merge happened on our end when a fix was done in this file for 5.7.3 which result in the bug.
This is resolved in 5.8, if you want to check the function code: https://github.com/EpicGames/UnrealEngine/blob/33eb75646531cca254bfdb80326c303b3eb96072/Engine/Plugins/PCG/Source/PCG/Private/Elements/PCGSplineSampler.cpp#L228

Differences for the bad merge: https://www.diffchecker.com/Cc0BhSw5/