1/**************************************************************************** 2** 3** Copyright (C) 2014 NVIDIA Corporation. 4** Copyright (C) 2019 The Qt Company Ltd. 5** Contact: https://www.qt.io/licensing/ 6** 7** This file is part of Qt 3D Studio. 8** 9** $QT_BEGIN_LICENSE:GPL$ 10** Commercial License Usage 11** Licensees holding valid commercial Qt licenses may use this file in 12** accordance with the commercial license agreement provided with the 13** Software or, alternatively, in accordance with the terms contained in 14** a written agreement between you and The Qt Company. For licensing terms 15** and conditions see https://www.qt.io/terms-conditions. For further 16** information use the contact form at https://www.qt.io/contact-us. 17** 18** GNU General Public License Usage 19** Alternatively, this file may be used under the terms of the GNU 20** General Public License version 3 or (at your option) any later version 21** approved by the KDE Free Qt Foundation. The licenses are as published by 22** the Free Software Foundation and appearing in the file LICENSE.GPL3 23** included in the packaging of this file. Please review the following 24** information to ensure the GNU General Public License requirements will 25** be met: https://www.gnu.org/licenses/gpl-3.0.html. 26** 27** $QT_END_LICENSE$ 28** 29****************************************************************************/ 30 31 32float simpleFresnel( in vec3 N, in float ior, float fresnelPower ) 33{ 34 float F = ((1.0-ior) * (1.0-ior)) / ((1.0+ior) * (1.0+ior)); 35 float fresnelGlancingAngle = clamp( 1.0 - dot(viewDir, N), 0.0, 1.0 ); 36 float ratio = F + (1.0 - F) * pow(fresnelGlancingAngle, fresnelPower); 37 38 return ratio; 39} 40 41// PKC : A variation on the simple Schlick approach that also handles the characteristic 42// "dip" that metals exhibit. The dip is very mild or virtually nonexisting in dielectrics, 43// but shows up in metals because of their strong incident reflectivity, and also allows for 44// colored metals like gold or copper to show their Fresnel hue shift as well because certain 45// components will have different baseline responses. 46vec3 pseudoFresnel( in vec3 N, in vec3 ior, float fresnelPower ) 47{ 48 vec3 F0 = ((vec3(1.0)-ior) * (vec3(1.0)-ior)) / ((vec3(1.0)+ior) * (vec3(1.0)+ior)); 49 50 float fresnelGlancingAngle = clamp( 1.0 - dot(viewDir, N), 0.0, 1.0 ); 51 52 float fresCurve = pow(fresnelGlancingAngle, fresnelPower); 53 vec3 dipCurve = F0 * sin( 3.1415926535 * fresCurve ) * 0.31830988618; 54 55 vec3 retCol = (vec3(1.0) - F0) * fresCurve; 56 retCol += F0 - dipCurve; 57 return clamp(retCol, 0.0, 1.0); 58} 59 60// look here: http://en.wikipedia.org/wiki/Fresnel_equations 61float fresnel( in float eta1, in float eta2, in float cosTheta1 ) 62{ 63 float etaInv = eta1 / eta2; 64 float cosTheta2 = 1.0 - ( 1.0 - cosTheta1 * cosTheta1 ) * ( etaInv * etaInv ); 65 if ( 0.0 <= cosTheta2 ) 66 { 67 cosTheta2 = sqrt( cosTheta2 ); 68 float n1t1 = eta1 * cosTheta1; 69 float n1t2 = eta1 * cosTheta2; 70 float n2t1 = eta2 * cosTheta1; 71 float n2t2 = eta2 * cosTheta2; 72 float rs = ( n1t1 - n2t2 ) / ( n1t1 + n2t2 ); 73 float rp = ( n1t2 - n2t1 ) / ( n1t2 + n2t1 ); 74 float f = 0.5 * ( rs * rs + rp * rp ); 75 return( clamp( f, 0.0, 1.0 ) ); 76 } 77 else 78 { 79 return( 1.0 ); 80 } 81} 82 83// we assume, light rays run through air with ior == 1.0 84// with eta = eta2 / eta1, we have 85// - when hitting a front face: eta2 == ior, eta1 == 1.0 => eta = ior 86// - when hitting a back face : eta2 == 1.0, eta1 == ior => eta = 1.0 / ior 87vec3 fresnel( in vec3 N, in vec3 ior ) 88{ 89 float cosTheta1 = dot( N, viewDir ); 90 if ( gl_FrontFacing ) 91 { 92 return( vec3( fresnel( 1.0, ior[0], cosTheta1 ), fresnel( 1.0, ior[1], cosTheta1 ), fresnel( 1.0, ior[2], cosTheta1 ) ) ); 93 } 94 else 95 { 96 return( vec3( fresnel( ior[0], 1.0, cosTheta1 ), fresnel( ior[1], 1.0, cosTheta1 ), fresnel( ior[2], 1.0, cosTheta1 ) ) ); 97 } 98} 99 100vec4 fresnelLayer( in vec3 N, in vec3 ior, in float weight, in vec3 layercolor, in vec4 layer, in vec4 base, in float alpha ) 101{ 102 vec3 refl = reflect( -viewDir, N ); 103 float reflWt = clamp( dot( surfNormal, refl ) + 1.0, 0.0, 1.0 ); 104 105 vec3 fresColor = reflWt * weight * layercolor * pseudoFresnel( N, ior, 5.0 ); 106 107 return( vec4( mix( base.rgb, layer.rgb, fresColor ), mix(alpha, 1.0, luminance(fresColor)) ) ); 108} 109 110