keywords: [UE4]Movement与Navigation相关的API

角色转向时平滑过度

TopDown视角下，默认情况下，角色转向是瞬间硬切的，如何让角色转向时平滑过度？

修改两个属性：

  • Orient Rotation To Movement
  • Use Controller Rotation Yaw
ACharacter::bOrientRotationToMovement = true;
UCharacterMovementComponent::bUseControllerRotationYaw = false;

设置转向速率：UCharacterMovementComponent::RotateRate::Z

如何修改角色的最大移动速度
if (UCharacterMovementComponent* Movement = MyCharacter->GetCharacterMovement())
{
    Movement->MaxWalkSpeed *= 0.5;
}
如何修改角色的当前移动速度

Tick() 中执行：

GetCharacterMovement()->Velocity = FVector(0.f, 500.f, 0.f);
如何停止正在移动的Pawn
AController::StopMovement()
修改重力加速度(Gravity)

  • 编辑器中设置全局重力加速度
    Project Settings -》 Engine -》 Physics -》 Default Physics Settings -》 Default Gravity Z。

  • 运行时runtime期间设置全局重力加速度：

      AWorldSettings* MyWorldSetting=GetWorldSettings();
  MyWorldSetting->bGlobalGravitySet=true;
  MyWorldSetting->GlobalGravityZ = 900.f;

  • 设置单个角色的重力加速度（倍率）

      MyCharacter->GetCharacterMovement()->GravityScale = 100.f
飞行模式中的加速减速问题

CharacterMovement默认有一个加速效果（属性值为MaxAcceleration，默认为2048，表示加速率），如果MovementMode设置为Walking模式，当调用Controller->StopMovement()来立即停止移动； 但是Flying Mode时，即使不再执行AddMovementInput()，Actor仍然会继续滑行一段距离，如果希望此时立即停止不滑行，需要将减速速率（默认为0）设置为加速速率的大小：

GetCharacterMovement()->BrakingDecelerationFlying = GetCharacterMovement()->MaxAcceleration;
设置MovementMode时的注意事项

如果一个Actor被Spawn出来之后，其MovementMode默认状态是Walking，如果此时Spawn的位置在空中，在没有Controller对其Possess的情况下，其静止在空中，当Possess之后，MovementMode会自动变为Falling，如果想让其继续停留在空中(比如飞行类的角色)，此时再手动将其MovementMode设置为Flying。绝对不能在possess之前设置，否则设置状态会被引擎修改掉。

Controller.StopMovement()和MovementComponent.StopMovementImmediately()的区别

前者只执行：

PathFollowingComp->AbortMove(*this, FPathFollowingResultFlags::MovementStop);

后者先执行：

Velocity = FVector::ZeroVector;

接着再执行：

PathFollowingComp->AbortMove(*this, FPathFollowingResultFlags::MovementStop);

检测某个坐标点是否在navmesh内，即可以作为寻路的坐标点。 UNavigationSystem::TestPathSync 实例用法：

UNavigationSystem* const NavSys = GetWorld()->GetNavigationSystem();
const ANavigationData* NavData = NavSys->GetNavDataForProps(YourCharacter->GetNavAgentPropertiesRef());
FPathFindingQuery Query1(YourCharacter, *NavData, YourCharacter->GetNavAgentLocation(), TestLocation);
bool qrs1 = NavSys->TestPathSync(Query1);

UNavigationSystem::FindPathSync也可以判断，但是他会返回寻路结果，效率上没有TestPathSync快。 其他的API还有：

UNavigationSystem::ProjectPointToNavigation

4.20版本获取NavigationSystem方法：

UNavigationSystemV1* UNavigationSystemV1::GetNavigationSystem(UObject* WorldContextObject);

或者：

UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(GetWorld());

获取指定坐标投射到NavMesh上的坐标；获取指定半径内可以行走的NavMesh的坐标点（随机获取）（4.20及之前老版本）：

UNavigationSystem.h：

/** Project a point onto the NavigationData */
UFUNCTION(BlueprintPure, Category = "AI|Navigation", meta = (WorldContext = "WorldContextObject", DisplayName = "ProjectPointToNavigation", ScriptName = "ProjectPointToNavigation"))
static bool UNavigationSystemV1::K2_ProjectPointToNavigation(UObject* WorldContextObject, const FVector& Point, FVector& ProjectedLocation, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass, const FVector QueryExtent = FVector::ZeroVector);

/** Generates a random location reachable from given Origin location.
 *    @return Return Value represents if the call was successful */
UFUNCTION(BlueprintPure, Category = "AI|Navigation", meta = (WorldContext = "WorldContextObject", DisplayName = "GetRandomReachablePointInRadius", ScriptName = "GetRandomReachablePointInRadius"))
static bool UNavigationSystemV1::K2_GetRandomReachablePointInRadius(UObject* WorldContextObject, const FVector& Origin, FVector& RandomLocation, float Radius, ANavigationData* NavData = NULL, TSubclassOf<UNavigationQueryFilter> FilterClass = NULL);

/** Generates a random location in navigable space within given radius of Origin.
 *    @return Return Value represents if the call was successful */
UFUNCTION(BlueprintPure, Category = "AI|Navigation", meta = (WorldContext = "WorldContextObject", DisplayName = "GetRandomPointInNavigableRadius", ScriptName = "GetRandomPointInNavigableRadius"))
static bool UNavigationSystemV1::K2_GetRandomPointInNavigableRadius(UObject* WorldContextObject, const FVector& Origin, FVector& RandomLocation, float Radius, ANavigationData* NavData = NULL, TSubclassOf<UNavigationQueryFilter> FilterClass = NULL);

另外两个函数（4.20、4.21版本的非shipping打包模式可用，不知官方会不会在后续版本定为正式版的API）：

bool ProjectPointToNavigation(const FVector& Point, FNavLocation& OutLocation, const FVector& Extent = INVALID_NAVEXTENT, const FNavAgentProperties* AgentProperties = NULL, FSharedConstNavQueryFilter QueryFilter = NULL);

bool ProjectPointToNavigation(const FVector& Point, FNavLocation& OutLocation, const FVector& Extent = INVALID_NAVEXTENT, const ANavigationData* NavData = NULL, FSharedConstNavQueryFilter QueryFilter = NULL) const;

K2_ProjectPointToNavigation用法：

FVector SourceLoc(1000.f, 1000.f, 100.f);
FVector DestLoc;

if (UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(world))
{
    if (ANavigationData* NavData = NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate))
    {
        NavSys->K2_ProjectPointToNavigation(world, SourceLoc, DestLoc, NavData, nullptr);
    }
}
Difference between GetRandomReachablePointInRadius and GetRandomPointInNavigableRadius

OK, after some investigations and tests. I think I’ve got the idea.

So bool UNavigationSystem::GetRandomPointInNavigableRadius(const FVector& Origin, float Radius, FNavLocation& ResultLocation, ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter) const

will return a point on navmesh if succeed, but it doesn’t check whether the point is on a connected navmesh which the Origin (first parameter) is on.

So bool UNavigationSystem::GetRandomReachablePointInRadius(const FVector& Origin, float Radius, FNavLocation& ResultLocation, ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter) const

will return a point on navmesh if succeed, and it will make sure the point in on a connected navmesh with the Origin.

So if the Origin is off navmesh and we want to find a point on navmesh, we need to use GetRandomPointInNavigableRadius.

If the Origin is on navmesh and we want to find a point to move to, we can use GetRandomReachablePointInRadius.

Reference: What’s the difference between GetRandomReachablePointInRadius and GetRandomPointInNavigableRadius? In which case we should use which.
https://answers.unrealengine.com/questions/796996/whats-the-difference-between-getrandomreachablepoi.html?sort=oldest

寻路移动结束时的回调事件

代码：

UPathFollowingComponent::OnMoveFinished
如何获取两点之间的寻路路径(Vector数组)

代码：

//4.20之前版本用法：UNavigationSystem* NavSys = UNavigationSystem::GetCurrent(GetWorld());
UNavigationSystemV1* NavSys = UNavigationSystemV1::GetNavigationSystem(GetWorld());
 
UNavigationPath *tpath = NavSys->FindPathToLocationSynchronously(GetWorld(), GetActorLocation(), end_point);
     
if (tpath != NULL)
{
     for (int pointiter = 0; pointiter < tpath->PathPoints.Num(); pointiter++)
     {
         DrawDebugSphere(GetWorld(), tpath->PathPoints[pointiter], 10.0f, 12, FColor(255, 0, 0));
     }
}

参考：
https://answers.unrealengine.com/questions/102126/how-do-i-get-the-navigation-path-to-a-point.html

Notice

Compilation Error:

 error LNK2019: unresolved external symbol "__declspec(dllimport) public: static class UNavigationSystemV1 * __cdecl UNavigationSystemV1::GetNavigationSystem(class UObject *)" (__imp_?GetNavigationSystem@UNavigationSystemV1@@SAPEAV1@PEAVUObject@@@Z) referenced in function "protected: void __cdecl AMyPlayerController::SetNewMoveDestination(struct FVector)" (?SetNewMoveDestination@AMyPlayerController@@IEAAXUFVector@@@Z)
1>SkillJoystickPlayerController.cpp.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: static void __cdecl UNavigationSystemV1::SimpleMoveToLocation(class AController *,struct FVector const &)" (__imp_?SimpleMoveToLocation@UNavigationSystemV1@@SAXPEAVAController@@AEBUFVector@@@Z) referenced in function "protected: void __cdecl AMyPlayerController::SetNewMoveDestination(struct FVector)" (?SetNewMoveDestination@AMyPlayerController@@IEAAXUFVector@@@Z)

Solution:
Add NavigationSystem into DependencyModule. e.g.:

public class SkillJoystick : ModuleRules
{
    public SkillJoystick(ReadOnlyTargetRules Target) : base(Target)
    {
        PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;

        PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "NavigationSystem" });
    }
}

曾虑多情损梵行，入山又恐别倾城，世间安得双全法，不负如来不负卿。----仓央嘉措