UE4：AI‘s MoveTo——代码分析

文章目录

移动流程概述
调整方向
关于路径
UPathFollowingComponent
- 收到移动请求
- 更新路径
- 执行移动

移动流程概述

拉起一个UAITask_MoveTo，设置好InMoveRequest后，调用UAITask_MoveTo::PerformMove，内部转到AAIController::MoveTo。
判断是否到达，如果没有到达，就转到AAIController::RequestMove开始请求移动，内部创建一条路径后，传给UPathFollowingComponent::RequestMove，由UPathFollowingComponent完成一条路径的移动。
RequestMove调用SetMoveSegment处理出移动线段的信息。最后在Tick内通过这些线段完成移动。

void UGameplayTask::PerformActivation()
void UAITask_MoveTo::Activate()
void UAITask_MoveTo::ConditionalPerformMove()
void UAITask_MoveTo::PerformMove()
FPathFollowingRequestResult AAIController::MoveTo(const FAIMoveRequest& MoveRequest, FNavPathSharedPtr* OutPath)
FAIRequestID AAIController::RequestMove(const FAIMoveRequest& MoveRequest, FNavPathSharedPtr Path)
FAIRequestID UPathFollowingComponent::RequestMove(const FAIMoveRequest& RequestData, FNavPathSharedPtr InPath)Path = InPath;
void UPathFollowingComponent::SetMoveSegment(int32 SegmentStartIndex)void UPathFollowingComponent::UpdateMoveFocus()FVector UPathFollowingComponent::GetMoveFocus(bool bAllowStrafe) constvoid AAIController::SetFocalPoint(FVector NewFocus, EAIFocusPriority::Type InPriority)

在Tick内，调用FollowPathSegment，借助移动组件来完成Pawn的移动

void UPathFollowingComponent::TickComponent(float DeltaTime, enum ELevelTick TickType, FActorComponentTickFunction *ThisTickFunction)
void UPathFollowingComponent::FollowPathSegment(float DeltaTime)MovementComp->RequestPathMove(CurrentMoveInput);MovementComp->RequestDirectMove(MoveVelocity, bNotFollowingLastSegment);

如果使用了UCrowdFollowingComponent，则调用链则是：

void UCrowdManager::Tick(float DeltaTime)
void UCrowdManager::ApplyVelocity(UCrowdFollowingComponent* AgentComponent, int32 AgentIndex) const
void UCrowdFollowingComponent::ApplyCrowdAgentVelocity(const FVector& NewVelocity, const FVector& DestPathCorner, bool bTraversingLink, bool bIsNearEndOfPath)MovementComp->RequestPathMove(CurrentMoveInput);MovementComp->RequestDirectMove(MoveVelocity, bNotFollowingLastSegment);

调整方向

在过程中，会持续调用UpdateMoveFocus，进行任务朝向的设置

void UPathFollowingComponent::UpdateMoveFocus()
void AAIController::SetFocalPoint(FVector NewFocus, EAIFocusPriority::Type InPriority)

AAIController在Tick时进行旋转

void AAIController::Tick(float DeltaTime)
void AAIController::UpdateControlRotation(float DeltaTime, bool bUpdatePawn)

关于路径

初始路径在AAIController::MoveTo内确定，调用了找路径函数：

FPathFollowingRequestResult AAIController::MoveTo(const FAIMoveRequest& MoveRequest, FNavPathSharedPtr* OutPath)void AAIController::FindPathForMoveRequest(const FAIMoveRequest& MoveRequest, FPathFindingQuery& Query, FNavPathSharedPtr& OutPath) constUNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(GetWorld());if (NavSys){FPathFindingResult PathResult = NavSys->FindPathSync(Query);

找到路径后调用AAIController::RequestMove，转到UPathFollowingComponent::RequestMove

const FAIRequestID RequestID = Path.IsValid() ? RequestMove(MoveRequest, Path) : FAIRequestID::InvalidRequest;PathFollowingComponent->RequestMove(MoveRequest, Path);

UPathFollowingComponent使用这个路径，完成实际移动逻辑的控制

UPathFollowingComponent

收到移动请求

FAIRequestID UPathFollowingComponent::RequestMove(const FAIMoveRequest& RequestData, FNavPathSharedPtr InPath) // 那条线段可能开始减速UpdateDecelerationData();// 细节优化，前面两个点选哪个作为起点const uint32 CurrentSegment = DetermineStartingPathPoint(InPath.Get());// 设置线段信息为起点SetMoveSegment(CurrentSegment);

设置线段信息

void UPathFollowingComponent::SetMoveSegment(int32 SegmentStartIndex)// 获取起点和终点const FVector SegmentStart = *PathInstance->GetPathPointLocation(MoveSegmentStartIndex);FVector SegmentEnd = *CurrentDestination;// 移动方向MoveSegmentDirection = (SegmentEnd - SegmentStart).GetSafeNormal();// 判断是否使用了NavLinkif (PathPt0.CustomLinkId){UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(GetWorld());INavLinkCustomInterface* CustomNavLink = NavSys->GetCustomLink(PathPt0.CustomLinkId);StartUsingCustomLink(CustomNavLink, SegmentEnd);}// 跟新移动焦点UpdateMoveFocus();

跟新移动焦点

void UPathFollowingComponent::UpdateMoveFocus()// 计算焦点const FVector MoveFocus = GetMoveFocus(AIOwner->bAllowStrafe);if (bAllowStrafe && DestinationActor.IsValid()){MoveFocus = DestinationActor->GetActorLocation();}else{const FVector CurrentMoveDirection = GetCurrentDirection();// 会往前挪5米MoveFocus = *CurrentDestination + (CurrentMoveDirection * FAIConfig::Navigation::FocalPointDistance);}// 设置到AIController上AIOwner->SetFocalPoint(MoveFocus, EAIFocusPriority::Move);

更新路径

void UPathFollowingComponent::UpdatePathSegment()//路径失效的处理if (!Path->IsValid())// 到达：碰撞if (bCollidedWithGoal)// 到达：到达检查可接受半径的线段else if (MoveSegmentEndIndex > PreciseAcceptanceRadiusCheckStartNodeIndex && HasReachedDestination(CurrentLocation))// 最后一段，且是MoveToGoal，直接走过去else if (bFollowingLastSegment && bMoveToGoalOnLastSegment && bLastPathChunk)CurrentDestination.Set(NULL, GoalLocation);UpdateMoveFocus();// 到达else if (HasReachedCurrentTarget(CurrentLocation))// 阻塞检测const bool bHasNewSample = UpdateBlockDetection();if (bHasNewSample && IsBlocked())OnPathFinished(EPathFollowingResult::Blocked, FPathFollowingResultFlags::None);

执行移动

void UPathFollowingComponent::FollowPathSegment(float DeltaTime)// 判断是否需要减速const bool bAccelerationBased = MovementComp->UseAccelerationForPathFollowing();if (bAccelerationBased)if (MoveSegmentStartIndex >= DecelerationSegmentIndex)         if (bShouldDecelerate)const float SpeedPct = FMath::Clamp(FMath::Sqrt(DistToEndSq) / CachedBrakingDistance, 0.0f, 1.0f);CurrentMoveInput *= SpeedPct;MovementComp->RequestPathMove(CurrentMoveInput);// 直接移动FVector MoveVelocity = (CurrentTarget - CurrentLocation) / DeltaTime;PostProcessMove.ExecuteIfBound(this, MoveVelocity);MovementComp->RequestDirectMove(MoveVelocity, bNotFollowingLastSegment);