Function to advance to next frame

[xiubiuciu]

Hey guys, I am trying to use UE to do reinforcement learning and would like to build up a function similar to the step function inside OpenAI’s gym.
There’s a button on the top part of the editor, called advance to next frame, which could achieve what I want.
However, after searching, this button can’t be called in blueprint or c++. Is there any way to call this function? Appreciate any suggestions. Thank you in advance.

[3dRaven]

UI_COMMAND(SingleFrameAdvance, “Skip”, “Advances a single frame”, EUserInterfaceActionType::Button, FInputChord());

DebuggerCommands.cpp
in
\Engine\Source\Editor\UnrealEd\Private\Kismet2

Most likely this portion of code:

void FInternalPlayWorldCommandCallbacks::SingleFrameAdvance_Clicked()
{
	if (IsStoppedAtBreakpoint_InEngineMode())
	{
		return;
	}

	// We want to function just like Single stepping where we will stop at a breakpoint if one is encountered but we also want to stop after 1 tick if a breakpoint is not encountered.
	FKismetDebugUtilities::RequestSingleStepIn();
	if (HasPlayWorld())
	{
		GUnrealEd->PlayWorld->bDebugFrameStepExecution = true;
		LeaveDebuggingMode();
		GUnrealEd->PlaySessionSingleStepped();
	}
}

[xiubiuciu]

Thank you for your quick and excellent reply.

Can I ask what library you have included in your code? When I try to use them in my code, FKismetDebugUtilities and GUnrealEd cannot be recognized.

[3dRaven]

I’m still dissecting the unreal engine code to get it running from a static lib
So far it does pause the game but still doesn’t single step.

[xiubiuciu]

Really thrilled to hear that. Hope you can solve it. Thank you!

[3dRaven]

It was pretty tough. Had to dig through a lot of source code to get the needed functions step by step with namespaces etc. But it works

Remember it uses UnrealEd so if you need this as a tool for a game you are publishing you would need to export it to a plugin that is only for uncooked mode otherwise it will cause problems with packing.

edit: re-upload: forgot to add the function to public:

AdvanceFunctionLibrary.cpp (1.1 KB)
AdvanceFunctionLibrary.h (461 Bytes)

video of it in action

- YouTube

It’s a static library so just include

#include "AdvanceFunctionLibrary.h"

and then you can call

UAdvanceFunctionLibrary::StepAdvanceFrame();

[xiubiuciu]

Awsome! Thank you for your contribution!