UnrealEngineUWP/Engine/Shaders/Private/CommonViewUniformBuffer.ush

// Copyright 1998-2019 Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	CommonViewUniformBuffer.usf: Common view uniform buffer specifics
=============================================================================*/

#pragma once

/*
* @return tan(View.FieldOfViewWideAngles * .5)
*/
float2 GetTanHalfFieldOfView()
{
	return float2(View.ClipToView[0][0], View.ClipToView[1][1]);
}

float2 GetPrevTanHalfFieldOfView()
{
	return float2(View.PrevClipToView[0][0], View.PrevClipToView[1][1]);
}

// might be used by Custom material expressions (still best to wrap the custom node in a material function)
// @return 1 / tan(View.FieldOfViewWideAngles * .5)
float2 GetCotanHalfFieldOfView()
{
	return float2(View.ViewToClip[0][0], View.ViewToClip[1][1]);
}

// might be used by Custom material expressions (still best to wrap the custom node in a material function)
// @return previous 1 / tan(View.FieldOfViewWideAngles * .5)
float2 GetPrevCotanHalfFieldOfView()
{
	return float2(View.PrevViewToClip[0][0], View.PrevViewToClip[1][1]);
}

// Return the index of the frame.
uint GetPowerOfTwoModulatedFrameIndex(uint Pow2Modulus)
{
	// Bit masking of an uniform parameter is a scalar operation on modern hardware.
	return View.StateFrameIndex & uint(Pow2Modulus - 1);
}