Guys, you are evil 
You made me break my âdonât write any C++ code yourselfâ rule!
While the code is neat, it only works under very specific conditions.
- The viewpoint is only *named * camera in the comments, but itâs not the camera. Itâs the controlled pawn.
- Therefore it does not work with 3rd person or Top Down cameras, where the cameraâs location is different from the APawn.
- With non-character pawns (e.g. WheeledVehicle), it breaks down completely (because it fails to cast to ACharacter).
TL/DR, here is a version which uses the CameraManager and does not need the pawn at all.
Iâm actually bad at C++, so please cross-check before copying 
// HUDBlueprintLibrary.cpp
#include "YOUR_MODULE_NAME.h"
#include "HUDBlueprintLibrary.h"
void UHUDBlueprintLibrary::FindScreenEdgeLocationForWorldLocation(UObject* WorldContextObject, const FVector& InLocation, const float EdgePercent, FVector2D& OutScreenPosition, float& OutRotationAngleDegrees, bool &bIsOnScreen)
{
bIsOnScreen = false;
OutRotationAngleDegrees = 0.f;
if (!GEngine) return;
const FVector2D ViewportSize = FVector2D(GEngine->GameViewport->Viewport->GetSizeXY());
const FVector2D ViewportCenter = FVector2D(ViewportSize.X / 2, ViewportSize.Y / 2);
UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject);
if (!World) return;
APlayerController* PlayerController = (WorldContextObject ? UGameplayStatics::GetPlayerController(WorldContextObject, 0) : NULL);
if (!PlayerController) return;
APlayerCameraManager* ViewPointActor = (WorldContextObject ? UGameplayStatics::GetPlayerCameraManager(WorldContextObject, 0) : NULL);
// APawn* ViewPointActor = PlayerController->GetPawn();
if (!ViewPointActor) return;
// FVector Location = ViewPointActor->GetActorLocation();
FVector Location = ViewPointActor->GetCameraLocation();
FVector Forward = ViewPointActor->GetActorForwardVector();
FVector Offset = (InLocation - Location).GetSafeNormal();
float DotProduct = FVector::DotProduct(Forward, Offset);
bool bLocationIsBehindCamera = (DotProduct < 0);
if (bLocationIsBehindCamera)
{
// For behind the camera situation, we cheat a little to put the
// marker at the bottom of the screen so that it moves smoothly
// as you turn around. Could stand some refinement, but results
// are decent enough for most purposes.
FVector DiffVector = InLocation - Location;
FVector Inverted = DiffVector * -1.f;
FVector NewInLocation = Location * Inverted;
NewInLocation.Z -= 5000;
PlayerController->ProjectWorldLocationToScreen(NewInLocation, OutScreenPosition);
OutScreenPosition.Y = (EdgePercent * ViewportCenter.X) * 2.f;
OutScreenPosition.X = -ViewportCenter.X - OutScreenPosition.X;
}
PlayerController->ProjectWorldLocationToScreen(InLocation, OutScreenPosition);//*ScreenPosition);
// Check to see if it's on screen. If it is, ProjectWorldLocationToScreen is all we need, return it.
if (OutScreenPosition.X >= 0.f && OutScreenPosition.X <= ViewportSize.X
&& OutScreenPosition.Y >= 0.f && OutScreenPosition.Y <= ViewportSize.Y)
{
bIsOnScreen = true;
return;
}
OutScreenPosition -= ViewportCenter;
float AngleRadians = FMath::Atan2(OutScreenPosition.Y, OutScreenPosition.X);
AngleRadians -= FMath::DegreesToRadians(90.f);
OutRotationAngleDegrees = FMath::RadiansToDegrees(AngleRadians) + 180.f;
float Cos = cosf(AngleRadians);
float Sin = -sinf(AngleRadians);
OutScreenPosition = FVector2D(ViewportCenter.X + (Sin * 180.f), ViewportCenter.Y + Cos * 180.f);
float m = Cos / Sin;
FVector2D ScreenBounds = ViewportCenter * EdgePercent;
if (Cos > 0)
{
OutScreenPosition = FVector2D(ScreenBounds.Y / m, ScreenBounds.Y);
}
else
{
OutScreenPosition = FVector2D(-ScreenBounds.Y / m, -ScreenBounds.Y);
}
if (OutScreenPosition.X > ScreenBounds.X)
{
OutScreenPosition = FVector2D(ScreenBounds.X, ScreenBounds.X*m);
}
else if (OutScreenPosition.X < -ScreenBounds.X)
{
OutScreenPosition = FVector2D(-ScreenBounds.X, -ScreenBounds.X*m);
}
OutScreenPosition += ViewportCenter;
}