最简单的 UE 4 C++ 教程 —— 给 Actor 添加径向推力十八
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原教程是基于 UE 4.18,我是基于 UE 4.25】
接上一节教程,本教程非常有趣,我们将通过在设定范围内的所有物体上添加径向推力来模拟爆炸。
创建一个名为 AddRadialForce 的新角色。我们不需要对头文件做任何操作。下面是由虚幻生成的默认头文件。
AddRadialForce.h
#pragma once
#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "AddRadialForce.generated.h"
UCLASS()
class UNREALCPP_API AAddRadialForce : public AActor
{
GENERATED_BODY()
public:
// Sets default values for this actor's properties
AAddRadialForce();
protected:
// Called when the game starts or when spawned
virtual void BeginPlay() override;
public:
// Called every frame
virtual void Tick(float DeltaTime) override;
};
为了在调试过程中提供帮助,让我们将 DrawDebugHelpers 头文件添加到代码中。
#include "AddRadialForce.h"
// add debug helpfers
#include "DrawDebugHelpers.h"
在这个例子中,我们将在 BeginPlay() 函数中执行所有的逻辑。我们想要收集我们范围内的所有命中结果,并从范围的扫描中获得结果。为此,我们将使用 TArray 跟踪重叠的 actor。
void AAddRadialForce::BeginPlay()
{
Super::BeginPlay();
// create tarray for hit results
TArray<FHitResult> OutHits;
// crate tarray for sweep actors
TArray<AActor*> SweepActors;
}
接下来我们要声明 TArray 数组 OutHits 。我们希望扫描范围从 actor 的位置开始同时也从该位置结束,并让 CollisionShape 是一个 500 单位的球体。您可以使用 GetActorLocation() 来获取 actor 的位置,它返回一个向量。我们使用 FCollisionShape:: makephere (500.0f) 来创建一个CollisionShape。
// Called when the game starts or when spawned
void AAddRadialForce::BeginPlay()
{
Super::BeginPlay();
// create tarray for hit results
TArray<FHitResult> OutHits;
// get actor locations
FVector MyLocation = GetActorLocation();
// start and end locations. The sphere will create the radial sweep.
FVector Start = MyLocation;
FVector End = MyLocation;
// create a collision sphere
FCollisionShape MyColSphere = FCollisionShape::MakeSphere(500.0f);
}
为了可视化扫描的球体,我们将绘制一个调试球体。
// Called when the game starts or when spawned
void AAddRadialForce::BeginPlay()
{
Super::BeginPlay();
// create tarray for hit results
TArray<FHitResult> OutHits;
// get actor locations
FVector MyLocation = GetActorLocation();
// start and end locations. The sphere will create the radial sweep.
FVector Start = MyLocation;
FVector End = MyLocation;
// create a collision sphere
FCollisionShape MyColSphere = FCollisionShape::MakeSphere(500.0f);
// draw collision sphere
DrawDebugSphere(GetWorld(), GetActorLocation(), MyColSphere.GetSphereRadius(), 50, FColor::Cyan, true);
}
接下来我们要检查我们的 actor 在我们 BeginPlay() 时是否击中了任何东西。每个 actor 都有GetWorld 功能。从 ,我们将使用从 GetWorld() 函数得到的 SweepMultiByChannel() 函数并对其设置上面刚创建的变量作为参数。这将返回一个 bool,指示是否有其他 actor 在该 actor 的范围内。
void AAddRadialForce::BeginPlay()
{
Super::BeginPlay();
// create tarray for hit results
TArray<FHitResult> OutHits;
// get actor locations
FVector MyLocation = GetActorLocation();
// start and end locations. The sphere will create the radial sweep.
FVector Start = MyLocation;
FVector End = MyLocation;
// create a collision sphere
FCollisionShape MyColSphere = FCollisionShape::MakeSphere(500.0f);
// draw collision sphere
DrawDebugSphere(GetWorld(), GetActorLocation(), MyColSphere.GetSphereRadius(), 50, FColor::Cyan, true);
// check if something got hit in the sweep
bool isHit = GetWorld()->SweepMultiByChannel(OutHits, Start, End, FQuat::Identity, ECC_WorldStatic, MyColSphere);
}
如果 isHit 为真,我们将通过遍历数组 OutHits ,并向每个成功 cast 的 actor 的根组件添加径向推力。
if (isHit)
{
// loop through TArray
for (auto& Hit : OutHits)
{
UStaticMeshComponent* MeshComp = Cast<UStaticMeshComponent>((Hit.GetActor())->GetRootComponent());
if (MeshComp)
{
// alternivly you can use ERadialImpulseFalloff::RIF_Linear for the impulse to get linearly weaker as it gets further from origin.
// set the float radius to 500 and the float strength to 2000.
MeshComp->AddRadialImpulse(GetActorLocation(), 500.f, 2000.f, ERadialImpulseFalloff::RIF_Constant, true);
}
}
}
最终完整 cpp 代码如下
#include "AddRadialForce.h"
// add debug helpfers
#include "DrawDebugHelpers.h"
// Sets default values
AAddRadialForce::AAddRadialForce()
{
// Set this actor to call Tick() every frame. You can turn this off to improve performance if you don't need it.
PrimaryActorTick.bCanEverTick = true;
}
// Called when the game starts or when spawned
void AAddRadialForce::BeginPlay()
{
Super::BeginPlay();
// create tarray for hit results
TArray<FHitResult> OutHits;
// get actor locations
FVector MyLocation = GetActorLocation();
// start and end locations. The sphere will create the radial sweep.
FVector Start = MyLocation;
FVector End = MyLocation;
// create a collision sphere
FCollisionShape MyColSphere = FCollisionShape::MakeSphere(500.0f);
// draw collision sphere
DrawDebugSphere(GetWorld(), GetActorLocation(), MyColSphere.GetSphereRadius(), 50, FColor::Cyan, true);
// check if something got hit in the sweep
bool isHit = GetWorld()->SweepMultiByChannel(OutHits, Start, End, FQuat::Identity, ECC_WorldStatic, MyColSphere);
if (isHit)
{
// loop through TArray
for (auto& Hit : OutHits)
{
UStaticMeshComponent* MeshComp = Cast<UStaticMeshComponent>((Hit.GetActor())->GetRootComponent());
if (MeshComp)
{
// alternivly you can use ERadialImpulseFalloff::RIF_Linear for the impulse to get linearly weaker as it gets further from origin.
// set the float radius to 500 and the float strength to 2000.
MeshComp->AddRadialImpulse(GetActorLocation(), 500.f, 2000.f, ERadialImpulseFalloff::RIF_Constant, true);
}
}
}
}
// Called every frame
void AAddRadialForce::Tick(float DeltaTime)
{
Super::Tick(DeltaTime);
}
实际运行起来的效果图如下
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