Timeline "Reverse from End" can have wrong direction at start

Development Programming & Scripting Blueprint
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1

After calling “Reverse from End” from timeline on first tick of “Update” the timeline’s Direction can be “Forward” not “Backward”. It depends on previous played direction.

Tested on 4.15.3 and 4.16.2

Example on picture:

191548-2017-07-03_17-41-12.png
191548-2017-07-03_17-41-12.png1097×519 83.3 KB

:

  1. Press Q
  2. Wait till finished
  3. Press W

And in logs you’ll find something like this:

LogBlueprintUserMessages: [BP_Timeline_154] Forward | 0.983359
LogBlueprintUserMessages: [BP_Timeline_154] Forward | 0.991692
LogBlueprintUserMessages: [BP_Timeline_154] Forward | 1.0
LogBlueprintUserMessages: [BP_Timeline_154] ------
LogBlueprintUserMessages: [BP_Timeline_154] Forward | 1.0       <<<<<
LogBlueprintUserMessages: [BP_Timeline_154] Backward | 0.991666
LogBlueprintUserMessages: [BP_Timeline_154] Backward | 0.983333

And if you press W again:

LogBlueprintUserMessages: [BP_Timeline_154] Backward | 0.015384
LogBlueprintUserMessages: [BP_Timeline_154] Backward | 0.007051
LogBlueprintUserMessages: [BP_Timeline_154] Backward | 0.0
LogBlueprintUserMessages: [BP_Timeline_154] ------
LogBlueprintUserMessages: [BP_Timeline_154] Backward | 1.0      <<<<<
LogBlueprintUserMessages: [BP_Timeline_154] Backward | 0.991666
LogBlueprintUserMessages: [BP_Timeline_154] Backward | 0.983333
1 Like
2

According to log, everything is fine.

Every time you press Q, timeline will play from 0

Every time you press W, timeline will play from 1

If you want to play from previous result, you must use simple Play/Reverse, not “from Start/End”

1 Like
3

Look at Direction in logs (where <<<<<<<). it should be “Backward” in both cases coz I start playing from end to start position.

Now it looks like, “oh. Im playing to the end… oh. im already on it, let’s go back to start”.

4

Issue still present on 4.23…

5

LogBlueprintUserMessages: [BP_Pawn_test_C_0] Forward::: 0.916669
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Forward::: 0.933336
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Forward::: 0.950003
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Forward::: 0.966669
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Forward::: 0.983336
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Forward::: 1.0
LogBlueprintUserMessages: [BP_Pawn_test_C_0] finish
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Forward::: 1.0
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Backward::: 0.983333
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Backward::: 0.966667
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Backward::: 0.95
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Backward::: 0.933333
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Backward::: 0.916666
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Backward::: 0.9
LogBlueprintUserMessages: [BP_Pawn_test_C_0] Backward::: 0.883333

just to keep this up, ISSUE STILL EXISTS IN 5.2! But still thank this post, just for knowing that the bug I ran into wasn’t my problem. Hope it could be fix.

6

UE 5.3: Ran as expected and suddenly I get this weird behavior. My work-around is to check timeline->IsPlaying() in the callback. When it returns false (and it does!) I early exit the callback. Now it works consistently as expected. Should be solved by Unreal, tho.

7

Can confirm this bug still exists in 5.4.

@K3Z4 can you share a screenshot of what you mean? I’ve tried a few variations of what I think you mean, but nothing seems to help the timeline Reverse from End properly even though it will Play from Start just fine.

8 
void YourClass::Init() 
{
   timeline.BindUFunction(this, callback) ; 
   // where callback = FName("<YourCallbackFunctionName>")
}

in your callback right at the start:

void YourClass::<YourCallbackFunctionName>
{
	if (!(timeline->IsPlaying())) {
		// very weird bug: you can get this callback when not yet playing...
		return;
	}
	
	// actual implementation of your callback
}