Project World to Screen Location stops returning a value

[daniel_alves_br]

@Paul Schultz

I wanted projections from behind the player also, so I dropped more or less what TheJamsh above has into a function that closely matches UE 4.14 ProjectWorldToScreen.

Declared:

UFUNCTION(BlueprintPure, Category = "UI Math")
static bool ProjectWorldToScreenBidirectional(APlayerController const* Player, const FVector& WorldPosition, FVector2D& ScreenPosition, bool& bTargetBehindCamera, bool bPlayerViewportRelative = false);

Defined:

bool UIBlueprintFunctionLibrary::ProjectWorldToScreenBidirectional(APlayerController const* Player, const FVector& WorldPosition, FVector2D& ScreenPosition, bool& bTargetBehindCamera, bool bPlayerViewportRelative)
{
FVector Projected;
bool bSuccess = false;

ULocalPlayer* const LP = Player ? Player->GetLocalPlayer() : nullptr;
if (LP && LP->ViewportClient)
{
// get the projection data
FSceneViewProjectionData ProjectionData;
if (LP->GetProjectionData(LP->ViewportClient->Viewport, eSSP_FULL, /*out*/ ProjectionData))
{
const FMatrix ViewProjectionMatrix = ProjectionData.ComputeViewProjectionMatrix();
const FIntRect ViewRectangle = ProjectionData.GetConstrainedViewRect();

FPlane Result = ViewProjectionMatrix.TransformFVector4(FVector4(WorldPosition, 1.f));
if (Result.W < 0.f) { bTargetBehindCamera = true; }
if (Result.W == 0.f) { Result.W = 1.f; } // Prevent Divide By Zero

const float RHW = 1.f / FMath::Abs(Result.W);
Projected = FVector(Result.X, Result.Y, Result.Z) * RHW;

// Normalize to 0..1 UI Space
const float NormX = (Projected.X / 2.f) + 0.5f;
const float NormY = 1.f - (Projected.Y / 2.f) - 0.5f;

Projected.X = (float)ViewRectangle.Min.X + (NormX * (float)ViewRectangle.Width());
Projected.Y = (float)ViewRectangle.Min.Y + (NormY * (float)ViewRectangle.Height());

bSuccess = true;
ScreenPosition = FVector2D(Projected.X, Projected.Y);

if (bPlayerViewportRelative)
{
ScreenPosition -= FVector2D(ProjectionData.GetConstrainedViewRect().Min);
}
}
else
{
ScreenPosition = FVector2D(1234, 5678);
}
}

return bSuccess;
}

Looks like:

I suggest you to add na ELSE parameter to set bTargetBehindCamera back to false when look to the tag point again.

if (Result.W < 0.f) { bTargetBehindCamera = true; } else {bTargetBehindCamera = false;}