FVector4 LensPrincipalPointOffsetScale
In some cases, the principal point of the lens is not at the center of the screen, especially for overlapped tile rendering. So given a UV in [-1,1] viewport space, convert it to the [-1,1] viewport space of the lens using LensUV = LensPrincipalPointOffsetScale.xy ScreenUV * LensPrincipalPointOffsetScale.zw; This value is FVector4(0,0,1,1) unless overridden.