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// This code contains NVIDIA Confidential Information and is disclosed
// under the Mutual Non-Disclosure Agreement.
//
// Notice
// ALL NVIDIA DESIGN SPECIFICATIONS AND CODE ("MATERIALS") ARE PROVIDED "AS IS" NVIDIA MAKES
// NO REPRESENTATIONS, WARRANTIES, EXPRESSED, IMPLIED, STATUTORY, OR OTHERWISE WITH RESPECT TO
// THE MATERIALS, AND EXPRESSLY DISCLAIMS ANY IMPLIED WARRANTIES OF NONINFRINGEMENT,
// MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE.
//
// NVIDIA Corporation assumes no responsibility for the consequences of use of such
// information or for any infringement of patents or other rights of third parties that may
// result from its use. No license is granted by implication or otherwise under any patent
// or patent rights of NVIDIA Corporation. No third party distribution is allowed unless
// expressly authorized by NVIDIA. Details are subject to change without notice.
// This code supersedes and replaces all information previously supplied.
// NVIDIA Corporation products are not authorized for use as critical
// components in life support devices or systems without express written approval of
// NVIDIA Corporation.
//
// Copyright (c) 2003 - 2016 NVIDIA Corporation. All rights reserved.
//
// NVIDIA Corporation and its licensors retain all intellectual property and proprietary
// rights in and to this software and related documentation and any modifications thereto.
// Any use, reproduction, disclosure or distribution of this software and related
// documentation without an express license agreement from NVIDIA Corporation is
// strictly prohibited.
//
/*
Define the shader permutations for code generation
%% MUX_BEGIN %%
%% MUX_END %%
*/
#include "ShaderCommon.h"
// using the phase functions directly isn't correct, because they are supposed to be
// integrated over the subtended solid angle. This falls apart as sin(theta)
// approaches 0 (ie. cos(theta) aproaches +1 or -1).
// We apply a sliding scale to the functions to compensate for this somewhat.
#define NORMALIZE_PHASE_FUNCTIONS 1
float ScatterPhase_Isotropic()
{
return 1.f / (4.f * PI);
}
float ScatterPhase_Rayleigh(float cosa)
{
float cos_term = cosa*cosa; // ^2
float phase_term = (3.f/(16.f*PI)) * (1.f + cos_term);
#if NORMALIZE_PHASE_FUNCTIONS
cos_term *= cos_term; // ^4
return phase_term*(1-cos_term/8.f);
#else
return phase_term;
#endif
}
float ScatterPhase_HenyeyGreenstein(float cosa, float g)
{
#if NORMALIZE_PHASE_FUNCTIONS
// "normalized" Henyey-Greenstein
float g_sqr = g*g;
float num = (1 - abs(g));
float denom = sqrt( max(1-2*g*cosa+g_sqr, 0) );
float frac = num/denom;
float scale = g_sqr + (1 - g_sqr) / (4*PI);
return scale * (frac*frac*frac);
#else
// Classic Henyey-Greenstein
float k1 = (1.f-g*g);
float k2 = (1.f + g*g - 2.f*g*cosa);
return (1.f / (4.f*PI)) * k1 / pow(abs(k2), 1.5f);
#endif
}
float ScatterPhase_MieHazy(float cosa)
{
float cos_term = 0.5f*(1+cosa);
float cos_term_2 = cos_term*cos_term; // ^2
float cos_term_4 = cos_term_2*cos_term_2; // ^4
float cos_term_8 = cos_term_4*cos_term_4; // ^8
float phase_term = (1.f/(4.f*PI))*(0.5f+(9.f/2.f)*cos_term_8);
#if NORMALIZE_PHASE_FUNCTIONS
return phase_term * (1-cos_term_8/2.0f);
#else
return phase_term;
#endif
}
float ScatterPhase_MieMurky(float cosa)
{
float cos_term = 0.5f*(1+cosa);
float cos_term_2 = cos_term*cos_term; // ^2
float cos_term_4 = cos_term_2*cos_term_2; // ^4
float cos_term_8 = cos_term_4*cos_term_4; // ^8
float cos_term_16 = cos_term_8*cos_term_8; // ^16
float cos_term_32 = cos_term_16*cos_term_16; // ^32
float phase_term = (1.f/(4.f*PI))*(0.5f+(33.f/2.f)*cos_term_32);
#if NORMALIZE_PHASE_FUNCTIONS
return phase_term * (1-cos_term_32/2.0f);
#else
return phase_term;
#endif
}
float4 main(VS_QUAD_OUTPUT input) : SV_TARGET
{
float cos_theta = -cos(PI*input.vTex.y);
float3 phase_factor = float3(0,0,0);
float3 total_scatter = float3(0,0,0);
// These must match the PhaseFunctionType enum in NvVolumetricLighting.h
static const uint PHASEFUNC_ISOTROPIC = 0;
static const uint PHASEFUNC_RAYLEIGH = 1;
static const uint PHASEFUNC_HG = 2;
static const uint PHASEFUNC_MIEHAZY = 3;
static const uint PHASEFUNC_MIEMURKY = 4;
for (uint i=0; i<g_uNumPhaseTerms; ++i)
{
float3 term_scatter = g_vPhaseParams[i].rgb;
total_scatter += term_scatter;
if (g_uPhaseFunc[i] == PHASEFUNC_ISOTROPIC)
{
phase_factor += term_scatter*ScatterPhase_Isotropic();
}
else if (g_uPhaseFunc[i] == PHASEFUNC_RAYLEIGH)
{
phase_factor += term_scatter*ScatterPhase_Rayleigh(cos_theta);
}
else if (g_uPhaseFunc[i] == PHASEFUNC_HG)
{
phase_factor += term_scatter*ScatterPhase_HenyeyGreenstein(cos_theta, g_vPhaseParams[i].a);
}
else if (g_uPhaseFunc[i] == PHASEFUNC_MIEHAZY)
{
phase_factor += term_scatter*ScatterPhase_MieHazy(cos_theta);
}
else if (g_uPhaseFunc[i] == PHASEFUNC_MIEMURKY)
{
phase_factor += term_scatter*ScatterPhase_MieMurky(cos_theta);
}
}
phase_factor = phase_factor / total_scatter;
return float4(phase_factor, 1);
}
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