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一、LerpTransformByCurve函数
可以根据曲线，平滑的对变换进行插值（按引用），相当于使用曲线替换Lerp节点的Alpha值。其返回值表示是否到达插值终点。参数解释：
const FTransform& Start??? 插值的起点变换
FTransform& Current??? 当前的变换（按引用），可以被曲线平滑改变
const FTransform& Target??? 插值的终点变换
const UCurveFloat* Curve????透明度曲线，其取值在0到1之间，以便进行Lerp插值
float& CurveTime????曲线的当前时间
const float& DeltaSeconds????场景时间
static bool LerpTransformByCurve(const FTransform& Start,FTransform& Current,const FTransform& Target,const UCurveFloat* Curve,float& CurveTime,const float& DeltaSeconds)
{
??? if(Curve)
?? ?{
?? ??? ?CurveTime = CurveTime + DeltaSeconds;
?? ??? ?float MinTime,MaxTime;
?? ??? ?Curve->GetTimeRange(MinTime,MaxTime);
?? ??? ?CurveTime = FMath::Clamp(CurveTime,MinTime,MaxTime);
?? ??? ?FTransform LerpTransform = UKismetMathLibrary::TLerp(Start,Target,Curve->GetFloatValue(CurveTime),ELerpInterpolationMode::DualQuatInterp);
?? ??? ?//直接赋值，不考虑过渡
?? ??? ?//Current = LerpTransform;
?? ??? ?//使用插值赋值较为平滑
?? ??? ?Current = UKismetMathLibrary::TInterpTo(Current,LerpTransform,DeltaSeconds,20.0f);
?? ??? ?if(CurveTime >= MaxTime)
?? ??? ?{
?? ??? ??? ?CurveTime = 0.0f;
?? ??? ??? ?return true;
?? ??? ?}
?? ?}
?? ?return false;
}
需要在Tick内使用。用法举例：
FTransform Start = 起始值;//假设已经赋值了
FTransform End = 终点值;//假设已经赋值了
float MyCurveTime = 0.0f;//假设从曲线起始时间向后进行插值
void AMyClass::Tick(float DeltaSeconds)
{
?? ?Super::Tick(DeltaSeconds);
?? ?//用一个bool控制是否进行插值
?? ?if (bLerpMyTransform)
??? {
????? //用IsFinished取得返回值，如果为true表示已经插值完毕，如果为false表示还没有插值到终点
????? bool IsFinished = LerpTransformByCurve(Start,MyTransform,End,MyCurve,MyCurveTime,DeltaSeconds);
????? //ON TICK
????? if (IsFinished)
????? {
??????? //ON FINISHED
??????? //如果插值完毕，就停止插值
??????? bLerpMyTransform = false;
????? }
????? //在插值的过程中，MyTransform、MyCurveTime会一直保持更新，随时可以直接使用
??? }
}
二、LerpFloatByCurve函数
static bool LerpFloatByCurve(const float& Start,float& Current,const float& Target,const UCurveFloat* Curve,float& CurveTime,const float& DeltaSeconds)
{
??? if(Curve)
?? ?{
?? ??? ?CurveTime = CurveTime + DeltaSeconds;
?? ??? ?float MinTime,MaxTime;
?? ??? ?Curve->GetTimeRange(MinTime,MaxTime);
?? ??? ?CurveTime = FMath::Clamp(CurveTime,MinTime,MaxTime);
?? ??? ?float LerpFloat = UKismetMathLibrary::Lerp(Start,Target,Curve->GetFloatValue(CurveTime));
?? ??? ?//直接赋值，不考虑过渡
?? ??? ?//Current = LerpFloat;
?? ??? ?//使用插值赋值较为平滑
?? ??? ?Current = UKismetMathLibrary::FInterpTo(Current,LerpFloat,DeltaSeconds,20.0f);
?? ??? ?if(CurveTime >= MaxTime)
?? ??? ?{
?? ??? ??? ?CurveTime = 0.0f;
?? ??? ??? ?return true;
?? ??? ?}
?? ?}
?? ?return false;
}
三、当然，更加优雅的方式
/**
?* 根据曲线对变换进行平滑插值，这相当于于使用浮点曲线控制Lerp的Alpha值
?* 注册委托是被允许的，可以使用委托在插值的不同阶段添加行为
?* 但请注意，句柄被CleanTimer销毁后仍然会继续运作，需要使用ClearAllTimersForObject才能销毁。
?*/
DECLARE_DELEGATE(FOnLerpTick);
DECLARE_DELEGATE(FOnLerpFinished);
DECLARE_DELEGATE(FOnLerpStop);
USTRUCT(BlueprintType)
struct FLerpTransformByCurve
{
?? ?GENERATED_BODY()
public:
?? ?FOnLerpTick OnTick;
?? ?FOnLerpFinished OnFinished;
?? ?FOnLerpStop OnStop;
?? ?void StartLerp(UWorld* InWorld,FTransform& Target,FTransform const& A,FTransform const& B,UCurveFloat* Curve,float& CurveTime,
?? ??? ?float const& TimerRate,bool const& bForceStopExistingTimer=true)
?? ?{
?? ??? ?if(bForceStopExistingTimer)
?? ??? ?{
?? ??? ??? ?StopLerp(InWorld);
?? ??? ?}
?? ??? ?TimerCallBack = FTimerDelegate::CreateRaw(this, &FLerpTransformByCurve::LerpBody,InWorld,&Target,A,B,
?? ??? ??? ?Curve,&CurveTime,TimerRate);
?? ??? ?InWorld->GetTimerManager().SetTimer(TimerHandle, TimerCallBack, TimerRate, true);
?? ?}
?? ?void StopLerp(const UWorld* InWorld) const
?? ?{
?? ??? ?//ON STOP
?? ??? ?OnStop.ExecuteIfBound();
?? ??? ?InWorld->GetTimerManager().ClearAllTimersForObject(this);
?? ?}
private:
?? ?FTimerHandle TimerHandle;
?? ?FTimerDelegate TimerCallBack;
?? ?void LerpBody(UWorld* InWorld,FTransform* Target,FTransform A,FTransform B,UCurveFloat* Curve,float* CurveTime,float DeltaSeconds)
?? ?{
?? ??? ?const bool IsFinished = this->LerpTransformByCurve(*Target,A,B,Curve,*CurveTime,DeltaSeconds);
?? ??? ?//ON TICK
?? ??? ?OnTick.ExecuteIfBound();
?? ??? ?if( IsFinished )
?? ??? ?{
?? ??? ??? ?//ON FINISHED
?? ??? ??? ?OnFinished.ExecuteIfBound();
?? ??? ??? ?StopLerp(InWorld);
?? ??? ?}
?? ?}
?? ?static bool LerpTransformByCurve(FTransform& Target,const FTransform& A,const FTransform& B,const UCurveFloat* Curve,float& CurveTime,const float& DeltaSeconds)
?? ?{
?? ??? ?if(Curve)
?? ??? ?{
?? ??? ??? ?CurveTime = CurveTime + DeltaSeconds;
?? ??? ??? ?float MinTime,MaxTime;
?? ??? ??? ?Curve->GetTimeRange(MinTime,MaxTime);
?? ??? ??? ?CurveTime = FMath::Clamp(CurveTime,MinTime,MaxTime);
?? ??? ??? ?const FTransform LerpTransform = UKismetMathLibrary::TLerp(A,B,Curve->GetFloatValue(CurveTime),ELerpInterpolationMode::DualQuatInterp);
?? ??? ??? ?Target = UKismetMathLibrary::TInterpTo(Target,LerpTransform,DeltaSeconds,20.0f);
?? ??? ??? ?if(CurveTime >= MaxTime)
?? ??? ??? ?{
?? ??? ??? ??? ?CurveTime = 0.0f;
?? ??? ??? ??? ?return true;
?? ??? ??? ?}
?? ??? ?}
?? ??? ?return false;
?? ?}
};
FLerpTransformByCurve LerpTransformByCurve;
//可以使用LerpTransformByCurve.OnFinished等来Bind其他事件
LerpTransformByCurve.StartLerp(GetWorld(),MyTransform,Start,End,MyCurve,MyCurveTime,G