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605 lines
22 KiB
Plaintext
605 lines
22 KiB
Plaintext
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.
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/*=============================================================================
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AtmosphereCommon.usf: Functions and variables shared by both rendering and precomputation
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This code contains embedded portions of free sample source code from
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http://www-evasion.imag.fr/Membres/Eric.Bruneton/PrecomputedAtmosphericScattering2.zip, Author: Eric Bruneton,
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08/16/2011, Copyright (c) 2008 INRIA, All Rights Reserved, which have been altered from their original version.
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Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
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1. Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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3. Neither the name of the copyright holders nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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=============================================================================*/
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#ifndef __ATMOSPHERE_COMMON__
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#define __ATMOSPHERE_COMMON__
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const static float AverageGroundRelectance = 0.1f; // Simple approximation ground reflection light
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/** Magic numbers are based on paper (http://hal.inria.fr/docs/00/28/87/58/PDF/article.pdf) */
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/** Rayleigh scattering terms */
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const static float3 BetaRayleighScattering = float3(5.8e-3f, 1.35e-2f, 3.31e-2f); // Equation 1, REK 04
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/** Mie scattering terms */
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const static float HeightScaleMie = 1.2f; // 1.2 km, for Mie scattering
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const static float3 BetaMieScattering = float3(4e-3f, 4e-3f, 4e-3f); // Equation 4
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const static float BetaRatio = 0.9f; // Figure 6, BetaMScattering/BetaMExtinction = 0.9
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const static float3 BetaMieExtinction = BetaMieScattering / BetaRatio.rrr;
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const static float MieG = 0.8f; // Equation 4
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const static float RadiusGround = 6360;
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const static float RadiusAtmosphere = 6430;
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const static float RadiusLimit = 6431;
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const static int IrradianceTexWidth = 64;
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const static int IrradianceTexHeight = 16;
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const static int InscatterMuNum = 128;
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const static int InscatterMuSNum = 32;
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const static int InscatterNuNum = 8;
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#define TRANSMITTANCE_NON_LINEAR 1
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#define INSCATTER_NON_LINEAR 1
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#define ATMOSPHERIC_TEXTURE_SAMPLE_FIX 1
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#ifndef ATMOSPHERIC_NO_SUN_DISK
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#define ATMOSPHERIC_NO_SUN_DISK 0
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#endif
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#ifndef ATMOSPHERIC_NO_GROUND_SCATTERING
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#define ATMOSPHERIC_NO_GROUND_SCATTERING 0
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#endif
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#ifndef ATMOSPHERIC_NO_DECAY
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#define ATMOSPHERIC_NO_DECAY 0
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#endif
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#ifndef RENDERFLAG_DISABLE_SUN_DISK
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#define RENDERFLAG_DISABLE_SUN_DISK 1 // E_DisableSunDisk = 1,
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#endif
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#ifndef RENDERFLAG_DISABLE_GROUND_SCATTERING
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#define RENDERFLAG_DISABLE_GROUND_SCATTERING 2 // E_DisableGroundScattering = 2,
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#endif
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/** Textures for rendering */
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Texture2D AtmosphereTransmittanceTexture;
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SamplerState AtmosphereTransmittanceTextureSampler;
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Texture2D AtmosphereIrradianceTexture;
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SamplerState AtmosphereIrradianceTextureSampler;
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Texture3D AtmosphereInscatterTexture;
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SamplerState AtmosphereInscatterTextureSampler;
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struct FAtmosphereVSOutput
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{
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float2 OutTexCoord : TEXCOORD0;
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float4 OutPosition : SV_POSITION;
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};
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float2 GetTransmittanceUV(float Radius, float Mu)
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{
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float U, V;
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#if TRANSMITTANCE_NON_LINEAR
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V = sqrt((Radius - RadiusGround) / (RadiusAtmosphere - RadiusGround));
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U = atan((Mu + 0.15) / (1.0 + 0.15) * tan(1.5)) / 1.5;
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#else
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V = (Radius - RadiusGround) / (RadiusAtmosphere - RadiusGround);
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U = (Mu + 0.15) / (1.0 + 0.15);
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#endif
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return float2(U, V);
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}
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void GetTransmittanceRMuS(float2 UV, out float Radius, out float MuS)
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{
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Radius = UV.y;
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MuS = UV.x;
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#if TRANSMITTANCE_NON_LINEAR
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Radius = RadiusGround + (Radius * Radius) * (RadiusAtmosphere - RadiusGround);
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MuS = -0.15 + tan(1.5 * MuS) / tan(1.5) * (1.0 + 0.15);
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#else
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r = RadiusGround + r * (RadiusAtmosphere - RadiusGround);
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muS = -0.15 + muS * (1.0 + 0.15);
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#endif
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}
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float2 GetIrradianceUV(float Radius, float MuS)
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{
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float V = (Radius - RadiusGround) / (RadiusAtmosphere - RadiusGround);
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float U = (MuS + 0.2) / (1.0 + 0.2);
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return float2(U, V);
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}
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void GetIrradianceRMuS(float2 UV, out float Radius, out float MuS)
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{
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Radius = RadiusGround + (UV.y * float(IrradianceTexHeight) - 0.5) / (float(IrradianceTexHeight) - 1.0) * (RadiusAtmosphere - RadiusGround);
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MuS = -0.2 + (UV.x * float(IrradianceTexWidth) - 0.5) / (float(IrradianceTexWidth) - 1.0) * (1.0 + 0.2);
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}
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float4 Texture4DSample(Texture3D Texture, SamplerState TextureSampler, float Radius, float Mu, float MuS, float Nu)
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{
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float H = sqrt(RadiusAtmosphere * RadiusAtmosphere - RadiusGround * RadiusGround);
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float Rho = sqrt(Radius * Radius - RadiusGround * RadiusGround);
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#if INSCATTER_NON_LINEAR
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float RMu = Radius * Mu;
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float Delta = RMu * RMu - Radius * Radius + RadiusGround * RadiusGround;
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float4 TexOffset = RMu < 0.0 && Delta > 0.0 ? float4(1.0, 0.0, 0.0, 0.5 - 0.5 / float(InscatterMuNum)) : float4(-1.0, H * H, H, 0.5 + 0.5 / float(InscatterMuNum));
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float MuR = 0.5 / float(View.AtmosphericFogInscatterAltitudeSampleNum) + Rho / H * (1.0 - 1.0 / float(View.AtmosphericFogInscatterAltitudeSampleNum));
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float MuMu = TexOffset.w + (RMu * TexOffset.x + sqrt(Delta + TexOffset.y)) / (Rho + TexOffset.z) * (0.5 - 1.0 / float(InscatterMuNum));
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// paper formula
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//float MuMuS = 0.5 / float(InscatterMuSNum) + max((1.0 - exp(-3.0 * MuS - 0.6)) / (1.0 - exp(-3.6)), 0.0) * (1.0 - 1.0 / float(InscatterMuSNum));
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// better formula
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float MuMuS = 0.5 / float(InscatterMuSNum) + (atan(max(MuS, -0.1975) * tan(1.26 * 1.1)) / 1.1 + (1.0 - 0.26)) * 0.5 * (1.0 - 1.0 / float(InscatterMuSNum));
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#else
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float MuR = 0.5 / float(View.AtmosphericFogInscatterAltitudeSampleNum) + Rho / H * (1.0 - 1.0 / float(View.AtmosphericFogInscatterAltitudeSampleNum));
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float MuMu = 0.5 / float(InscatterMuNum) + (Mu + 1.0) * 0.5f * (1.0 - 1.0 / float(InscatterMuNum));
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float MuMuS = 0.5 / float(InscatterMuSNum) + max(MuS + 0.2, 0.0) / 1.2 * (1.0 - 1.0 / float(InscatterMuSNum));
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#endif
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float LerpValue = (Nu + 1.0) * 0.5f * (float(InscatterNuNum) - 1.0);
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float MuNu = floor(LerpValue);
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LerpValue = LerpValue - MuNu;
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return Texture3DSampleLevel(Texture, TextureSampler, float3((MuNu + MuMuS) / float(InscatterNuNum), MuMu, MuR), 0) * (1.0 - LerpValue) +
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Texture3DSampleLevel(Texture, TextureSampler, float3((MuNu + MuMuS + 1.0) / float(InscatterNuNum), MuMu, MuR), 0) * LerpValue;
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}
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float Mod(float X, float Y)
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{
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return X - Y * floor(X/Y);
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}
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void GetMuMuSNu(float2 UV, float Radius, float4 DhdH, out float Mu, out float MuS, out float Nu)
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{
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float X = UV.x * float(InscatterMuSNum * InscatterNuNum) - 0.5;
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float Y = UV.y * float(InscatterMuNum) - 0.5;
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#if INSCATTER_NON_LINEAR
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if (Y < float(InscatterMuNum) * 0.5f)
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{
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float D = 1.0 - Y / (float(InscatterMuNum) * 0.5f - 1.0);
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D = min(max(DhdH.z, D * DhdH.w), DhdH.w * 0.999);
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Mu = (RadiusGround * RadiusGround - Radius * Radius - D * D) / (2.0 * Radius * D);
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Mu = min(Mu, -sqrt(1.0 - (RadiusGround / Radius) * (RadiusGround / Radius)) - 0.001);
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}
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else
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{
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float D = (Y - float(InscatterMuNum) * 0.5f) / (float(InscatterMuNum) * 0.5f - 1.0);
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D = min(max(DhdH.x, D * DhdH.y), DhdH.y * 0.999);
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Mu = (RadiusAtmosphere * RadiusAtmosphere - Radius * Radius - D * D) / (2.0 * Radius * D);
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}
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MuS = Mod(X, float(InscatterMuSNum)) / (float(InscatterMuSNum) - 1.0);
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// paper formula
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//MuS = -(0.6 + log(1.0 - MuS * (1.0 - exp(-3.6)))) / 3.0;
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// better formula
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MuS = tan((2.0 * MuS - 1.0 + 0.26) * 1.1) / tan(1.26 * 1.1);
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Nu = -1.0 + floor(X / float(InscatterMuSNum)) / (float(InscatterNuNum) - 1.0) * 2.0;
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#else
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Mu = -1.0 + 2.0 * Y / (float(InscatterMuNum) - 1.0);
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MuS = Mod(X, float(InscatterMuSNum)) / (float(InscatterMuSNum) - 1.0);
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MuS = -0.2 + MuS * 1.2;
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Nu = -1.0 + floor(X / float(InscatterMuSNum)) / (float(InscatterNuNum) - 1.0) * 2.0;
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#endif
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}
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/**
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* Nearest intersection of ray r,mu with ground or top atmosphere boundary
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* mu=cos(ray zenith angle at ray origin)
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*/
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float Limit(float Radius, float Mu)
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{
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float Dout = -Radius * Mu + sqrt(Radius * Radius * (Mu * Mu - 1.0) + RadiusLimit * RadiusLimit);
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float Delta2 = Radius * Radius * (Mu * Mu - 1.0) + RadiusGround * RadiusGround;
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if (Delta2 >= 0.0)
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{
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float Din = -Radius * Mu - sqrt(Delta2);
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if (Din >= 0.0)
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{
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Dout = min(Dout, Din);
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}
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}
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return Dout;
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}
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/**
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* Transmittance(=transparency) of atmosphere for infinite ray (r,mu)
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* (mu=cos(view zenith angle)), intersections with ground ignored
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*/
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float3 Transmittance(float Radius, float Mu)
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{
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float2 UV = GetTransmittanceUV(Radius, Mu);
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return Texture2DSampleLevel(AtmosphereTransmittanceTexture, AtmosphereTransmittanceTextureSampler, UV, 0).rgb;
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}
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/**
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* Transmittance(=transparency) of atmosphere for infinite ray (r,mu)
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* (mu=cos(view zenith angle)), or zero if ray intersects ground
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*/
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float3 TransmittanceWithShadow(float Radius, float Mu)
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{
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// Need to correct calculation based on shadow feature, currently don't consider
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//return Mu < -sqrt(1.0 - (RadiusGround / Radius) * (RadiusGround / Radius)) ? float3(0.f, 0.f, 0.f) : Transmittance(Radius, Mu);
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return Transmittance(Radius, Mu);
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}
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/**
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* Transmittance(=transparency) of atmosphere between x and x0
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* Assume segment x,x0 not intersecting ground
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* D = Distance between x and x0, mu=cos(zenith angle of [x,x0) ray at x)
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*/
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float3 TransmittanceWithDistance(float Radius, float Mu, float D)
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{
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float3 Result;
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float R1 = sqrt(Radius * Radius + D * D + 2.0 * Radius * Mu * D);
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float Mu1 = (Radius * Mu + D) / R1;
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if (Mu > 0.0)
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{
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Result = min(Transmittance(Radius, Mu) / Transmittance(R1, Mu1), 1.0);
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}
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else
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{
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Result = min(Transmittance(R1, -Mu1) / Transmittance(Radius, -Mu), 1.0);
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}
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return Result;
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}
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/**
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* Transmittance(=transparency) of atmosphere between x and x0
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* Assume segment x,x0 not intersecting ground
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* Radius=||x||, Mu=cos(zenith angle of [x,x0) ray at x), v=unit direction vector of [x,x0) ray
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*/
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float3 TransmittanceWithDistance(float Radius, float Mu, float3 V, float3 X0)
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{
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float3 Result;
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float R1 = length(X0);
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float Mu1 = dot(X0, V) / Radius;
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if (Mu > 0.0)
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{
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Result = min(Transmittance(Radius, Mu) / Transmittance(R1, Mu1), 1.0);
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}
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else
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{
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Result = min(Transmittance(R1, -Mu1) / Transmittance(Radius, -Mu), 1.0);
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}
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return Result;
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}
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/**
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* Optical depth for ray (r,mu) of length d, using analytic formula
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* (mu=cos(view zenith angle)), intersections with ground ignored
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* H=height scale of exponential density function
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*/
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float OpticalDepthWithDistance(float H, float Radius, float Mu, float D)
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{
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float ParticleDensity = 6.2831; // REK 04, Table 2
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float A = sqrt((0.5/H)*Radius);
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float2 A01 = A * float2(Mu, Mu + D / Radius);
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float2 A01Sign = sign(A01);
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float2 A01Squared = A01*A01;
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float X = A01Sign.y > A01Sign.x ? exp(A01Squared.x) : 0.0;
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float2 Y = A01Sign / (2.3193*abs(A01) + sqrt(1.52*A01Squared + 4.0)) * float2(1.0, exp(-D/H*(D/(2.0*Radius)+Mu)));
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return sqrt((ParticleDensity*H)*Radius) * exp((RadiusGround-Radius)/H) * (X + dot(Y, float2(1.0, -1.0)));
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}
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float3 Irradiance(Texture2D Texture, SamplerState TextureSampler, float r, float muS)
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{
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float2 UV = GetIrradianceUV(r, muS);
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return Texture2DSampleLevel(Texture, TextureSampler, UV, 0).rgb;
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}
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/** Rayleigh phase function */
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float PhaseFunctionR(float Mu)
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{
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return (3.0 / (16.0 * PI)) * (1.0 + Mu * Mu);
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}
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/** Mie phase function */
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float PhaseFunctionM(float Mu)
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{
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return 1.5 * 1.0 / (4.0 * PI) * (1.0 - MieG * MieG) * pow( abs(1.0 + (MieG * MieG) - 2.0 * MieG * Mu), -3.0/2.0) * (1.0 + Mu * Mu) / (2.0 + MieG * MieG);
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}
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/** Approximated single Mie scattering (cf. approximate Cm in paragraph "Angular precision") */
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float3 GetMie(float4 RayMie)
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{
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// RayMie.rgb=C*, RayMie.w=Cm,r
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return RayMie.rgb * RayMie.w / max(RayMie.r, 1e-4) * (BetaRayleighScattering.rrr / BetaRayleighScattering.rgb);
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}
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/** Transmittance(=transparency) of atmosphere for ray (r,mu) of length d
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* (mu=cos(view zenith angle)), intersections with ground ignored
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* uses analytic formula instead of transmittance texture, REK 04, Atmospheric Transparency
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*/
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float3 AnalyticTransmittance(float R, float Mu, float D)
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{
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return exp(- BetaRayleighScattering * OpticalDepthWithDistance(View.AtmosphericFogHeightScaleRayleigh, R, Mu, D) - BetaMieExtinction * OpticalDepthWithDistance(HeightScaleMie, R, Mu, D));
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}
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static const float HeightOffset = 0.01f;
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/** inscattered light along ray x+tv, when sun in direction s (=S[L]-T(x,x0)S[L]|x0) */
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float3 GetInscatterColor(float FogDepth, float3 X, float T, float3 V, float3 S, float Radius, float Mu, out float3 Attenuation, bool bIsSceneGeometry)
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{
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float3 Result = float3(0.f, 0.f, 0.f); // X in space and ray looking in space, intialize
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Attenuation = float3(1.f, 1.f, 1.f);
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float D = -Radius * Mu - sqrt(Radius * Radius * (Mu * Mu - 1.0) + RadiusAtmosphere * RadiusAtmosphere);
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if (D > 0.0)
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{
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// if X in space and ray intersects atmosphere
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// move X to nearest intersection of ray with top atmosphere boundary
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X += D * V;
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T -= D;
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Mu = (Radius * Mu + D) / RadiusAtmosphere;
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Radius = RadiusAtmosphere;
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}
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float Epsilon = 0.005f;
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if (Radius < RadiusGround + HeightOffset + Epsilon)
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{
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float Diff = (RadiusGround + HeightOffset + Epsilon) - Radius;
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X -= Diff * V;
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T -= Diff;
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Radius = RadiusGround + HeightOffset + Epsilon;
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Mu = dot(X, V) / Radius;
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}
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if (Radius <= RadiusAtmosphere && FogDepth > 0.f)
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{
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float3 X0 = X + T * V;
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float R0 = length(X0);
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// if ray intersects atmosphere
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float Nu = dot(V, S);
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float MuS = dot(X, S) / Radius;
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float MuHorizon = -sqrt(1.0 - (RadiusGround / Radius) * (RadiusGround / Radius));
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if (bIsSceneGeometry)
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{
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Mu = max(Mu, MuHorizon + Epsilon + 0.15);
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}
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else
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{
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Mu = max(Mu, MuHorizon + Epsilon);
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}
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float MuOriginal = Mu;
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float BlendRatio = 0.0f;
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if (bIsSceneGeometry)
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{
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BlendRatio = saturate(exp(-V.z) - 0.5);
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if (BlendRatio < 1.f)
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{
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V.z = max(V.z, 0.15);
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V = normalize(V);
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float3 X1 = X + T * V;
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float R1 = length(X1);
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Mu = dot(X1, V) / R1;
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}
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}
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float PhaseR = PhaseFunctionR(Nu);
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float PhaseM = PhaseFunctionM(Nu);
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float4 Inscatter = max(Texture4DSample(AtmosphereInscatterTexture, AtmosphereInscatterTextureSampler, Radius, Mu, MuS, Nu), 0.0);
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if (T > 0.0)
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{
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#if ATMOSPHERIC_TEXTURE_SAMPLE_FIX
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// avoids imprecision problems in transmittance computations based on textures
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Attenuation = AnalyticTransmittance(Radius, Mu, T);
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#else
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Attenuation = TransmittanceWithDistance(Radius, Mu, V, X0);
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#endif
|
|
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float Mu0 = dot(X0, V) / R0;
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float MuS0 = dot(X0, S) / R0;
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|
|
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if (bIsSceneGeometry)
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|
{
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R0 = max(R0, Radius);
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|
}
|
|
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if (R0 > RadiusGround + HeightOffset)
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|
{
|
|
if (BlendRatio < 1.f)
|
|
{
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|
Inscatter = max(Inscatter - Attenuation.rgbr * Texture4DSample(AtmosphereInscatterTexture, AtmosphereInscatterTextureSampler, R0, Mu0, MuS0, Nu), 0.0);
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#if ATMOSPHERIC_TEXTURE_SAMPLE_FIX
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|
// avoids imprecision problems near horizon by interpolating between two points above and below horizon
|
|
if (!bIsSceneGeometry )
|
|
{
|
|
if (abs(Mu - MuHorizon) < Epsilon)
|
|
{
|
|
float Alpha = ((Mu - MuHorizon) + Epsilon) * 0.5f / Epsilon;
|
|
|
|
Mu = MuHorizon - Epsilon;
|
|
R0 = sqrt(Radius * Radius + T * T + 2.0 * Radius * T * Mu);
|
|
Mu0 = (Radius * Mu + T) / R0;
|
|
|
|
Mu0 = max(MuHorizon + Epsilon, Mu0);
|
|
float4 Inscatter0 = Texture4DSample(AtmosphereInscatterTexture, AtmosphereInscatterTextureSampler, Radius, Mu, MuS, Nu);
|
|
float4 Inscatter1 = Texture4DSample(AtmosphereInscatterTexture, AtmosphereInscatterTextureSampler, R0, Mu0, MuS0, Nu);
|
|
float4 InscatterA = max(Inscatter0 - Attenuation.rgbr * Inscatter1, 0.0);
|
|
|
|
Mu = MuHorizon + Epsilon;
|
|
R0 = sqrt(Radius * Radius + T * T + 2.0 * Radius * T * Mu);
|
|
|
|
Mu0 = (Radius * Mu + T) / R0;
|
|
Mu0 = max(MuHorizon + Epsilon, Mu0);
|
|
Inscatter0 = Texture4DSample(AtmosphereInscatterTexture, AtmosphereInscatterTextureSampler, Radius, Mu, MuS, Nu);
|
|
Inscatter1 = Texture4DSample(AtmosphereInscatterTexture, AtmosphereInscatterTextureSampler, R0, Mu0, MuS0, Nu);
|
|
float4 InscatterB = max(Inscatter0 - Attenuation.rgbr * Inscatter1, 0.0);
|
|
|
|
Inscatter = lerp(InscatterA, InscatterB, Alpha);
|
|
}
|
|
}
|
|
else if (BlendRatio > 0.f)
|
|
{
|
|
Inscatter = lerp(Inscatter,
|
|
(1.f - Attenuation.rgbr) * max(Texture4DSample(AtmosphereInscatterTexture, AtmosphereInscatterTextureSampler, Radius, MuOriginal, MuS, Nu), 0.0),
|
|
BlendRatio);
|
|
}
|
|
#endif
|
|
}
|
|
else
|
|
{
|
|
Inscatter = (1.f - Attenuation.rgbr) * Inscatter;
|
|
}
|
|
}
|
|
}
|
|
#if ATMOSPHERIC_TEXTURE_SAMPLE_FIX
|
|
// avoids imprecision problems in Mie scattering when sun is below horizon
|
|
Inscatter.w *= smoothstep(0.00, 0.02, MuS);
|
|
#endif
|
|
Result = max(Inscatter.rgb * PhaseR + GetMie(Inscatter) * PhaseM, 0.0);
|
|
}
|
|
|
|
return Result;
|
|
}
|
|
|
|
/**
|
|
* Ground radiance at end of ray x+tv, when sun in direction s
|
|
* attenuated bewteen ground and viewer (=R[L0]+R[L*])
|
|
*/
|
|
float3 GetGroundColor(float4 SceneColor, float3 X, float T, float3 V, float3 S, float Radius, float3 Attenuation, bool bIsSceneGeometry)
|
|
{
|
|
float3 Result = float3(0.f, 0.f, 0.f); // ray looking at the sky (for intial value)
|
|
if (T > 0.0)
|
|
{
|
|
// if ray hits ground surface
|
|
// ground Reflectance at end of ray, X0
|
|
float3 X0 = X + T * V;
|
|
float R0 = length(X0);
|
|
float3 N = X0 / R0;
|
|
N = X0 / R0;
|
|
SceneColor.xyz = saturate(SceneColor.xyz + 0.05);
|
|
|
|
float4 Reflectance = SceneColor * float4(0.2, 0.2, 0.2, 1.0);
|
|
|
|
// direct sun light (radiance) reaching X0
|
|
float MuS = dot(N, S);
|
|
float3 SunLight = bIsSceneGeometry ? float3(0.f, 0.f, 0.f) : TransmittanceWithShadow(R0, MuS);
|
|
|
|
// precomputed sky light (irradiance) (=E[L*]) at X0
|
|
float3 GroundSkyLight = Irradiance(AtmosphereIrradianceTexture, AtmosphereIrradianceTextureSampler, R0, MuS);
|
|
|
|
// light reflected at X0 (=(R[L0]+R[L*])/T(X,X0))
|
|
//
|
|
float3 GroundColor = (Reflectance.rgb * (max(MuS, 0.0) * SunLight + GroundSkyLight)) / PI;
|
|
|
|
// water specular color due to SunLight
|
|
if (!bIsSceneGeometry && Reflectance.w > 0.0)
|
|
{
|
|
float3 H = normalize(S - V);
|
|
float Fresnel = 0.02 + 0.98 * pow(1.0 - dot(-V, H), 5.0);
|
|
float WaterBrdf = Fresnel * pow(max(dot(H, N), 0.0), 150.0);
|
|
GroundColor += Reflectance.w * max(WaterBrdf, 0.0) * SunLight;
|
|
}
|
|
|
|
Result = Attenuation * GroundColor; //=R[L0]+R[L*]
|
|
}
|
|
return Result;
|
|
}
|
|
|
|
/** Direct sun light for ray x+tv, when sun in direction s (=L0) */
|
|
float3 GetSunColor(float3 X, float T, float3 V, float3 S, float Radius, float Mu)
|
|
{
|
|
float3 TransmittanceValue = Radius <= RadiusAtmosphere ? TransmittanceWithShadow(Radius, Mu) : float3(1.0, 1.0, 1.0); // T(X,xo)
|
|
if (T > 0.0)
|
|
{
|
|
return float3(0.f, 0.f, 0.f);
|
|
}
|
|
else
|
|
{
|
|
float SunIntensity = step(cos(PI * View.AtmosphericFogSunDiscScale / 180.0), dot(V, S)); // Lsun
|
|
return TransmittanceValue * SunIntensity; // Eq (9)
|
|
}
|
|
}
|
|
|
|
float4 GetAtmosphericFog(float3 ViewPosition, float3 ViewVector, float SceneDepth, float3 SceneColor)
|
|
{
|
|
float Scale = 0.00001f * View.AtmosphericFogDistanceScale;
|
|
ViewPosition.z = (ViewPosition.z - View.AtmosphericFogGroundOffset) * View.AtmosphericFogAltitudeScale;
|
|
ViewPosition *= Scale;
|
|
ViewPosition.z += RadiusGround + HeightOffset;
|
|
|
|
float Radius = length(ViewPosition);
|
|
|
|
float3 V = normalize(ViewVector.xyz);
|
|
|
|
float Mu = dot(ViewPosition, V) / Radius;
|
|
|
|
float T = -Radius * Mu - sqrt(Radius * Radius * (Mu * Mu - 1.0) + RadiusGround * RadiusGround);
|
|
|
|
float DepthThreshold = 100.f * View.AtmosphericFogDistanceScale; // 100km limit
|
|
SceneDepth *= Scale;
|
|
|
|
float FogDepth = max(0.f, SceneDepth - View.AtmosphericFogStartDistance);
|
|
float ShadowFactor = 1.f; // shadow approximation
|
|
float DistanceRatio = min(FogDepth * 0.1f / View.AtmosphericFogStartDistance, 1.f);
|
|
bool bIsSceneGeometry = (SceneDepth < DepthThreshold); // Assume as scene geometry
|
|
if (bIsSceneGeometry)
|
|
{
|
|
ShadowFactor = DistanceRatio * View.AtmosphericFogPower;
|
|
T = max(SceneDepth + View.AtmosphericFogDistanceOffset, 1.f);
|
|
}
|
|
|
|
float3 Attenuation;
|
|
|
|
float3 InscatterColor = GetInscatterColor(FogDepth, ViewPosition, T, V, View.AtmosphericFogSunDirection, Radius, Mu, Attenuation, bIsSceneGeometry); //S[L]-T(ViewPosition,xs)S[l]|xs
|
|
#if BASEPASS_ATMOSPHERIC_FOG // Transluceny rendering just follows normal render flag
|
|
float3 GroundColor = 0.f;
|
|
BRANCH
|
|
if ((View.AtmosphericFogRenderMask & RENDERFLAG_DISABLE_GROUND_SCATTERING) == 0)
|
|
{
|
|
GroundColor = GetGroundColor(float4(SceneColor.xyz, 1.f), ViewPosition, T, V, View.AtmosphericFogSunDirection, Radius, Attenuation, bIsSceneGeometry); //R[L0]+R[L*]
|
|
}
|
|
#else
|
|
#if MATERIAL_ATMOSPHERIC_FOG || ATMOSPHERIC_NO_GROUND_SCATTERING // Material doesn't need this ground scattering for now
|
|
float3 GroundColor = 0.f;
|
|
#else
|
|
float3 GroundColor = GetGroundColor(float4(SceneColor.xyz, 1.f), ViewPosition, T, V, View.AtmosphericFogSunDirection, Radius, Attenuation, bIsSceneGeometry); //R[L0]+R[L*]
|
|
#endif
|
|
#endif
|
|
|
|
#if BASEPASS_ATMOSPHERIC_FOG // Transluceny rendering just follows normal render flag
|
|
float3 Sun = 0.f;
|
|
BRANCH
|
|
if ((View.AtmosphericFogRenderMask & RENDERFLAG_DISABLE_SUN_DISK) == 0)
|
|
{
|
|
Sun = GetSunColor(ViewPosition, T, V, View.AtmosphericFogSunDirection, Radius, Mu); //L0
|
|
}
|
|
#else
|
|
#if MATERIAL_ATMOSPHERIC_FOG || ATMOSPHERIC_NO_SUN_DISK // Material doesn't need to render the sun disk
|
|
float3 Sun = 0.f;
|
|
#else
|
|
float3 Sun = GetSunColor(ViewPosition, T, V, View.AtmosphericFogSunDirection, Radius, Mu); //L0
|
|
#endif
|
|
#endif
|
|
|
|
// Decay color
|
|
float3 OriginalColor = Sun + GroundColor + InscatterColor;
|
|
OriginalColor = View.AtmosphericFogSunPower * ShadowFactor * View.AtmosphericFogSunColor.rgb * OriginalColor;
|
|
float4 OutColor = float4(OriginalColor, lerp(saturate(Attenuation.r * View.AtmosphericFogDensityScale - View.AtmosphericFogDensityOffset), 1.f, (1.f - DistanceRatio)) );
|
|
return OutColor;
|
|
}
|
|
|
|
float4 CalculateVertexAtmosphericFog(float3 WorldPosition, float3 InCameraPosition)
|
|
{
|
|
float3 ViewVector = WorldPosition - InCameraPosition;
|
|
float Distance = length(ViewVector);
|
|
return GetAtmosphericFog(InCameraPosition, ViewVector, Distance, float3(0.f, 0.f, 0.f));
|
|
}
|
|
|
|
#endif
|
|
|