Deproject Screen To World and SceneCapture2D.

Development Programming & Scripting C++
9

Here is a simple copy-paste from me ye olde function library:


void UGBFunctionLibrary::CaptureComponent2D_DeProject(class USceneCaptureComponent2D* Target, const FVector2D& ScreenPos, FVector& OutWorldOrigin, FVector& OutWorldDirection)
{
    if ((Target == nullptr) || (Target->TextureTarget == nullptr))
    {
        return;
    }

    const FTransform& Transform = Target->GetComponentToWorld();
    FMatrix ViewMatrix = Transform.ToInverseMatrixWithScale();
    FVector ViewLocation = Transform.GetTranslation();

    // swap axis st. x=z,y=x,z=y (unreal coord space) so that z is up
    ViewMatrix = ViewMatrix * FMatrix(
        FPlane(0,    0,    1,    0),
        FPlane(1,    0,    0,    0),
        FPlane(0,    1,    0,    0),
        FPlane(0,    0,    0,    1));

    const float FOV = Target->FOVAngle * (float)PI / 360.0f;

    FIntPoint CaptureSize(Target->TextureTarget->GetSurfaceWidth(), Target->TextureTarget->GetSurfaceHeight());

    float XAxisMultiplier;
    float YAxisMultiplier;

    if (CaptureSize.X > CaptureSize.Y)
    {
        // if the viewport is wider than it is tall
        XAxisMultiplier = 1.0f;
        YAxisMultiplier = CaptureSize.X / (float)CaptureSize.Y;
    }
    else
    {
        // if the viewport is taller than it is wide
        XAxisMultiplier = CaptureSize.Y / (float)CaptureSize.X;
        YAxisMultiplier = 1.0f;
    }

    FMatrix    ProjectionMatrix = FReversedZPerspectiveMatrix (
        FOV,
        FOV,
        XAxisMultiplier,
        YAxisMultiplier,
        GNearClippingPlane,
        GNearClippingPlane
        );

    const FMatrix InverseViewMatrix = ViewMatrix.InverseFast();
    const FMatrix InvProjectionMatrix = ProjectionMatrix.Inverse();

    const FIntRect ViewRect = FIntRect(0, 0, CaptureSize.X, CaptureSize.Y);

    FSceneView::DeprojectScreenToWorld(ScreenPos, ViewRect, InverseViewMatrix, InvProjectionMatrix, OutWorldOrigin, OutWorldDirection);
}

void UGBFunctionLibrary::Capture2D_DeProject(class ASceneCapture2D* Target, const FVector2D& ScreenPos, FVector& OutWorldOrigin, FVector& OutWorldDirection)
{
    if (Target)
    {
        CaptureComponent2D_DeProject(Target->GetCaptureComponent2D(), ScreenPos, OutWorldOrigin, OutWorldDirection);
    }
}

I can’t take any real credit for the guts of the function, which I think is taken from another area of the UE4 source and simply adjusted to suite use the scene components info.

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