I get this Error and the Editor crashes when i try to edit spline points after a while or after restarting the project:
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0xffffffffffffffff (SplineStreet.cpp:103)
Sometimes its on line 61 but I’m not sure why. When moving the same Spline Point it sometimes is this line and sometimes the other.
The Setup is as follows:
An Editable SplineComponent is the core component. On it SplineMeshComponents get added and two splines (curbs): one on the right, the other on the left side. They then get points assigned based on the MainSpline’s SplinePoints:
.cpp
#include "SplineStreet.h"
#include "Components/SplineComponent.h"
#include "Components/SplineMeshComponent.h"
#include "Components/TextRenderComponent.h"
// Sets default values
ASplineStreet::ASplineStreet()
{
// Set this actor to call Tick() every frame. You can turn this off to improve performance if you don't need it.
PrimaryActorTick.bCanEverTick = false;
MainSpline = CreateDefaultSubobject<USplineComponent>(TEXT("MainSpline"));
MainSpline->AttachToComponent(RootComponent, FAttachmentTransformRules::KeepRelativeTransform);
LeftCurbSpline = CreateDefaultSubobject<USplineComponent>(TEXT("LeftCurb"));
LeftCurbSpline->AttachToComponent(RootComponent, FAttachmentTransformRules::KeepRelativeTransform);
LeftCurbSpline->CreationMethod = EComponentCreationMethod::UserConstructionScript;
RightCurbSpline = CreateDefaultSubobject<USplineComponent>(TEXT("RightCurb"));
RightCurbSpline->AttachToComponent(RootComponent, FAttachmentTransformRules::KeepRelativeTransform);
RightCurbSpline->CreationMethod = EComponentCreationMethod::UserConstructionScript;
if (RoadMesh)
{
//set initial spline length to be exactly the size of one mesh
MainSpline->SetLocationAtSplinePoint(1, FVector(RoadMesh->GetBoundingBox().GetExtent().X * 2, 0, 0), ESplineCoordinateSpace::Local);
}
}
// Called when the game starts or when spawned
void ASplineStreet::BeginPlay()
{
Super::BeginPlay();
}
void ASplineStreet::OnConstruction(const FTransform& Transform)
{
if (RoadMesh) {
float Length = MainSpline->GetSplineLength();
float MeshHalfLength = RoadMesh->GetBoundingBox().GetExtent().X;
float MeshLength = MeshHalfLength * 2;
int32 NumOfMeshes = FMath::CeilToInt32(Length / MeshLength);
float SegmentLength = Length / NumOfMeshes;
//create all spline meshes for the road
PopulateMeshAlongSpline(MainSpline, RoadMesh);
//remove all points from curb splines
const int32 LeftNum = LeftCurbSpline->GetNumberOfSplinePoints();
for (int32 i = 0; i < LeftNum ; i++)
{
LeftCurbSpline->RemoveSplinePoint(i);
}
const int32 RightNum = RightCurbSpline->GetNumberOfSplinePoints();
for (int32 i = 0; i < RightNum; i++)
{
RightCurbSpline->RemoveSplinePoint(i);
}
//add spline points to curb splines
for (int32 i = 0; i < MainSpline->GetNumberOfSplinePoints(); i++)
{
FVector Tangent = MainSpline->GetTangentAtSplinePoint(i, ESplineCoordinateSpace::Local);
FVector LeftVec = Tangent.RotateAngleAxis(270.f, FVector(0, 0, 1));
FVector RightVec = Tangent.RotateAngleAxis(90.f, FVector(0, 0, 1));
LeftVec.GetSafeNormal();
LeftVec.Normalize();
RightVec.GetSafeNormal();
RightVec.Normalize();
float MeshHalfWidth = RoadMesh->GetBoundingBox().GetExtent().Y;
FVector RightOffset = RightVec * (MeshHalfWidth);// + CurbWidth);
FVector LeftOffset = LeftVec * MeshHalfWidth;
FVector PosAtPoint = MainSpline->GetLocationAtSplinePoint(i, ESplineCoordinateSpace::World);
FVector NewPosLeft = PosAtPoint + LeftOffset; //+ RootComponent->GetComponentLocation();
FVector NewPosRight = PosAtPoint + RightOffset; //+ RootComponent->GetComponentLocation();
if (i < LeftCurbSpline->GetNumberOfSplinePoints())
{
LeftCurbSpline->SetLocationAtSplinePoint(i, NewPosLeft, ESplineCoordinateSpace::Local);
}
else
{
LeftCurbSpline->AddSplinePoint(NewPosLeft, ESplineCoordinateSpace::Local);
}
if (i < RightCurbSpline->GetNumberOfSplinePoints())
{
RightCurbSpline->SetLocationAtSplinePoint(i, NewPosRight, ESplineCoordinateSpace::Local);
}
else
{
RightCurbSpline->AddSplinePoint(NewPosRight, ESplineCoordinateSpace::Local);
}
}
PopulateMeshAlongSpline(LeftCurbSpline, LeftCurbMesh, SplineMeshesLeftCurb);
PopulateMeshAlongSpline(RightCurbSpline, RightCurbMesh, SplineMeshesRightCurb);
}
}
.h
#pragma once
#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "Components/SplineComponent.h"
#include "Components/SplineMeshComponent.h"
#include "SplineStreet.generated.h"
UCLASS()
class SOLARDRIVE_API ASplineStreet : public AActor
{
GENERATED_BODY()
public:
// Sets default values for this actor's properties
ASplineStreet();
UPROPERTY(EditAnywhere)
UStaticMesh* RoadMesh;
UPROPERTY(EditAnywhere)
UStaticMesh* LeftCurbMesh;
UPROPERTY(EditAnywhere)
UStaticMesh* RightCurbMesh;
protected:
// Called when the game starts or when spawned
virtual void BeginPlay() override;
virtual void OnConstruction(const FTransform& Transform) override;
void PostEditChangeProperty(FPropertyChangedEvent& PropertyChangeEvent) override;
public:
// Called every frame
virtual void Tick(float DeltaTime) override;
private:
USplineComponent* MainSpline;
USplineComponent* LeftCurbSpline;
USplineComponent* RightCurbSpline;
TArray<USplineMeshComponent*> SplineMeshesLeftCurb;
TArray<USplineMeshComponent*> SplineMeshesRightCurb;
ESplineCoordinateSpace::Type SplineLocal = ESplineCoordinateSpace::Local;
void PopulateMeshAlongSpline(USplineComponent* Spline, UStaticMesh* Mesh, TArray<USplineMeshComponent*> SplineMeshes = {nullptr});
};
This works well for a while after placing the BP in the level, but after some time when i try to edit the Spline Points of the MainSpline, the Engine crashes.
I already updated the drivers. This is driving me crazy as im not sure what is going on here?!
I Would really appriciate some help 
Another minor problem is that the two curb splines path’s aren’t shown in the editor. They flicker for one frame in the BP inspector after clicking on “compile” and then go invisible - but that’s only on the side and not really that important.
