UE4 actor Basics

1.Actor Life cycle of

1.Actor The creation of

a. Load from disk , It is applicable to Actor establish .

Create a process ：

1.LoadMap or AddToWorld Called                    

2. Load... From disk Actor

3. perform PostLoad, You can perform custom versioning and repair operations .

4.InitializeActorsForPlay： initialization Actor

5. For uninitialized Actor perform RouteActorInitialize

6. Initialize components ：PreInitializeComponents - stay Actor Called on a component of InitializeComponent Call before

InitializeComponent - Actor Create helper function for each component defined on .

PostInitializeComponents - Actor After the component of is initialized, call

7.BeginPlay - Call after the level starts

b. Copy... From the editor .

Create a process ：

1. In the editor Actor Be copied into the new world scene

2.PostDuplicate Called

3.InitializeActorsForPlay： initialization Actor

4. For uninitialized Actor perform RouteActorInitialize

5. Initialize components ： ditto

6.BeginPlay - Call after the level starts

c. example Actor

Create a process ：

1.SpawnActor Called

2.PostSpawnInitialize

3.PostActorCreated The build function class behavior occurs here .PostActorCreated And PostLoad Mutually exclusive .

4.ExecuteConstruction：OnConstruction - Actor The construction of . The blueprint Actor Components of are created here , The blueprint variable is initialized here

5.PostActorConstruction

6. Initialize components ： ditto

7.OnActorSpawned stay UWorld Play on

8.BeginPlay - Call after the level starts

d. Delay generation , Set any attribute to “Expose on Spawn” You can delay Actor Generation .

Create a process ：

1.SpawnActorDeferred - Generate programmed Actor, Make additional settings before the blueprint build script

2.PostSpawnInitialize

3.PostActorCreated The build function class behavior occurs here .PostActorCreated And PostLoad Mutually exclusive .

4. Through a valid but incomplete Actor Instance settings / Call multiple “ Initialization function ”

5.FinishSpawningActor - Post call pair Actor To be finalized , stay Spawn Actor Select from row ExecuteConstruction.

6.ExecuteConstruction：OnConstruction - Actor The construction of . The blueprint Actor Components of are created here , The blueprint variable is initialized here

7.PostActorConstruction

8. Initialize components ： ditto

9.OnActorSpawned stay UWorld Play on

10.BeginPlay - Call after the level starts

2.Actor Destruction of

Destruction process ：

a.EndPlay - Call... In several places , Guarantee Actor My life is coming to an end . call EndPlay The whole situation of ：

1. Yes Destroy Explicit call

2.Play in Editor End

3. Level transition （ Seamless travel or loading maps ） contain Actor The flow level of is unloaded

4.Actor Your life is over

5. Application shutdown （ All Actor Be destroyed ）

b. No matter how these situations occur ,Actor Will be marked as RF_PendingKill, So it will be deallocated in the next garbage collection cycle .

c. An object is marked for destruction for a period of time , Garbage collection actually removes it from memory , Release the resources it uses . Destruction process ：

1.BeginDestroy - Object can take advantage of this opportunity to free memory and process other multithreaded resources （ This is the image thread proxy object ）.

2.IsReadyForFinishDestroy - The garbage collection process will call this function , To determine whether an object can be permanently deallocated .

3.FinishDestroy - Finally the object will be destroyed , This is another opportunity to free up internal data structures .

2. Components ：

1. A component is a special type of object , As Actor Child objects in use .

2.ActorComponent Is the basic class of the component , Definitions can be added to different types Actor The reuse behavior of .

3. To make ActorComponent Every frame updates and affects the scene , They must be registered with the scene . call UActorComponent::RegisterComponent() Registration can be performed .

4. You can also cancel ActorComponent Registration of , Avoid them being updated 、 simulation , Or render . call UActorComponent::UnregisterComponent() You can cancel the component registration .

5.ActorComponent Through its TickComponent() Function to update every frame .

3. Generate Actor：

1. Create a new Actor The process of the example is called generation . Generate Actors The process is to use UWorld::SpawnActor() Function completed .

2.SpawnActor The structure of the class is as follows ：

AActor* UWorld::SpawnActor

(

                   UClass*         Class, Indicate the to be generated Actor Class .

                   FName           InName, Used as generated Actor The name of .

                   FVector const*  Location, Used as generated Actor Initial position .

                   FRotator const* Rotation, Used as generated Actor Initial rotation of .

                   AActor*         Template, Used as generated Actor The template used when . The generated Actor The template will be used Actor Property value of the .

                   bool            bNoCollisionFail, Decide to generate Actor Whether to carry out collision test . If true, It's generating Actor Do not conduct crash test .

                   bool            bRemoteOwned,

                   AActor*         Owner, Have the generated Actor Of AActor.

                   APawn*          Instigator, Resulting in the generated Actor A aggressor who inflicts harm .

                   bool            bNoFail, Determines if certain conditions are not met , Generate Actor Failure or not .

                   ULevel*         OverrideLevel, Specify generation Actor Of Ulevel, That is to say Actor External container for .

                   bool            bDeferConstruction, Decide whether to run the build script .

 )

3.SpawnActor() Function usage ：

AKAsset* SpawnedActor1 = (AKAsset*) GetWorld()->SpawnActor(AKAsset::StaticClass(), NAME_None, &Location);

4.Actor Ticking：

1.Tick Means at regular intervals （ Usually once per frame ） In a actor Or run a piece of code or blueprint script on a component .

2.Actors And components can be set to each frame tick, It can also be set at the lowest time interval tick, Or not at all tick. Besides , They can be combined into groups at different stages of the engine's update cycle per frame ; Separate instructions may also be accepted , Waiting for a specific tick When it's done, start again .

3.Tick Groups can be specified in code or blueprints . Every tick The group will complete each of the specified actor And components tick, Then start the next tick Group .

4. Can have playful tick Group has ：

        a.TG_PrePhysics：Actor With physical objects （ Including physical based attachments ） Used when interacting tick Group .

               this tick The physical simulation data in belongs to the previous frame — That is, the data rendered to the screen in the previous frame .

        b.TG_DuringPhysics: this tick The group only recommends logic that ignores physical data or allows a frame deviation .

        c.TG_PostPhysics： This group can be used for weapon or motion tracking . When you render this frame, all physical objects will be in their final position .

        d.TG_PostUpdateWork: This group can send the most backward information to the particle system .

5. stay BeginPlay in ,actor Will register its master with the engine tick Functions and their components tick function .Actor Of tick The function can be passed through PrimaryActorTick Members are set to be in a specific tick Run in group , Or completely disable .

          The code is as follows ：

                  PrimaryActorTick.bCanEverTick = true;

                  PrimaryActorTick.bTickEvenWhenPaused = true;

                  PrimaryActorTick.TickGroup = TG_PrePhysics;

          Components Tick The function code is as follows ：

                  PrimaryComponentTick.bCanEverTick = true;

                  PrimaryComponentTick.bTickEvenWhenPaused = true;

                  PrimaryComponentTick.TickGroup = TG_PrePhysics;

6. Be careful ：PrimaryActorTick Use Actor Of Tick() function , and PrimaryComponentTick Use ActorComponent Of TickComponent() function .