From 0143d8d7d740858938456db31fbdc878d3430c1b Mon Sep 17 00:00:00 2001
From: Jb win <jbbriant@outlook.fr>
Date: Wed, 30 Apr 2025 13:47:42 +0700
Subject: [PATCH] FT - PostStep Update as a Delegate + Can be used to finely
 control actuators between mj_steps

---
 .../Private/Actors/MujocoVolumeActor.cpp       | 12 ++++++++++++
 .../Public/Actors/MujocoVolumeActor.h          | 18 ++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/Plugins/LuckyMujoco/Source/LuckyMujoco/Private/Actors/MujocoVolumeActor.cpp b/Plugins/LuckyMujoco/Source/LuckyMujoco/Private/Actors/MujocoVolumeActor.cpp
index 2aa1ba5e..d2c585b0 100644
--- a/Plugins/LuckyMujoco/Source/LuckyMujoco/Private/Actors/MujocoVolumeActor.cpp
+++ b/Plugins/LuckyMujoco/Source/LuckyMujoco/Private/Actors/MujocoVolumeActor.cpp
@@ -109,6 +109,12 @@ template <typename ComponentType> void AMujocoVolumeActor::AssignComponentsToArr
 	}
 }
 
+template <typename UserClass>
+void AMujocoVolumeActor::BindPostPhysicDelegate(UserClass* Object, void(UserClass::* Func)(float))
+{
+	PostPhysicUpdateDelegate.BindUObject(Object, Func);
+}
+
 void AMujocoVolumeActor::InitializeMujoco()
 {
 	if (!Options)
@@ -391,11 +397,17 @@ void AMujocoVolumeActor::Tick(float DeltaTime)
 {
 	if (MujocoData)
 	{
+		// TODO rename FrameSkip -> SimStepsPerGameFrame - Min 1 - Default 16
+		// TODO timestep default .001 (1ms)
+		// TODO mj_step only inside the for loop
+		
 		mj_step(MujocoModel.Get(), MujocoData.Get());
+		PostPhysicUpdateDelegate.ExecuteIfBound(MujocoData->time);
 
 		for (int32 Frame = 0; Frame < FrameSkip; ++Frame)
 		{
 			mj_step(MujocoModel.Get(), MujocoData.Get());
+			PostPhysicUpdateDelegate.ExecuteIfBound(MujocoData->time);
 		}
 
 		for (int32 i = 1; i < BodyComponents.Num(); ++i)
diff --git a/Plugins/LuckyMujoco/Source/LuckyMujoco/Public/Actors/MujocoVolumeActor.h b/Plugins/LuckyMujoco/Source/LuckyMujoco/Public/Actors/MujocoVolumeActor.h
index 12b041e8..8140dcc2 100644
--- a/Plugins/LuckyMujoco/Source/LuckyMujoco/Public/Actors/MujocoVolumeActor.h
+++ b/Plugins/LuckyMujoco/Source/LuckyMujoco/Public/Actors/MujocoVolumeActor.h
@@ -21,6 +21,10 @@ DECLARE_DYNAMIC_MULTICAST_DELEGATE(FOnMujocoCompileBegin);
 DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnMujocoCompileError, FString, Error);
 DECLARE_DYNAMIC_MULTICAST_DELEGATE(FOnMujocoCompileSuccess);
 
+// To be called after mj_step
+DECLARE_DELEGATE_OneParam(FPostPhysicUpdate, float);
+
+
 UCLASS(Blueprintable, BlueprintType)
 class LUCKYMUJOCO_API AMujocoVolumeActor : public AActor
 {
@@ -76,6 +80,20 @@ public:
 	UPROPERTY(BlueprintAssignable, Category = "Mujoco | Events")
 	FOnMujocoCompileSuccess OnMujocoCompileSuccess;
 
+	// ---------------------------
+	// ------- POST UPDATE -------
+	// ---------------------------
+private:
+	FPostPhysicUpdate PostPhysicUpdateDelegate;
+public:	
+	/**
+	 * @description Register a delegate to be executed after mj_step
+	 * @param Object
+	 */
+	template<typename UserClass>
+	void BindPostPhysicDelegate(UserClass* Object, void (UserClass::*Func)(float));
+	
+	
 	UFUNCTION(BlueprintCallable, Category = "Mujoco")
 	void SetActuatorValue(const FString& ActuatorName, double Value);