1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
|
/**
* Precomputed Atmospheric Scattering
* Copyright (c) 2008 INRIA
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* Author: Eric Bruneton
*/
// computes deltaJ (line 7 in algorithm 4.1)
uniform float r;
uniform vec4 dhdH;
uniform int layer;
uniform sampler2D deltaESampler;
uniform sampler3D deltaSRSampler;
uniform sampler3D deltaSMSampler;
uniform float first;
#ifdef _VERTEX_
void main() {
gl_Position = gl_Vertex;
}
#endif
#ifdef _GEOMETRY_
#extension GL_EXT_geometry_shader4 : enable
void main() {
gl_Position = gl_PositionIn[0];
gl_Layer = layer;
EmitVertex();
gl_Position = gl_PositionIn[1];
gl_Layer = layer;
EmitVertex();
gl_Position = gl_PositionIn[2];
gl_Layer = layer;
EmitVertex();
EndPrimitive();
}
#endif
#ifdef _FRAGMENT_
const float dphi = M_PI / float(INSCATTER_SPHERICAL_INTEGRAL_SAMPLES);
const float dtheta = M_PI / float(INSCATTER_SPHERICAL_INTEGRAL_SAMPLES);
void inscatter(float r, float mu, float muS, float nu, out vec3 raymie) {
r = clamp(r, Rg, Rt);
mu = clamp(mu, -1.0, 1.0);
muS = clamp(muS, -1.0, 1.0);
float var = ieeesqrt(1.0 - mu * mu) * ieeesqrt(1.0 - muS * muS);
nu = clamp(nu, muS * mu - var, muS * mu + var);
float cthetamin = -ieeesqrt(1.0 - (Rg / r) * (Rg / r));
vec3 v = vec3(ieeesqrt(1.0 - mu * mu), 0.0, mu);
float sx = v.x == 0.0 ? 0.0 : (nu - muS * mu) / v.x;
vec3 s = vec3(sx, ieeesqrt(max(0.0, 1.0 - sx * sx - muS * muS)), muS);
raymie = vec3(0.0);
// integral over 4.PI around x with two nested loops over w directions (theta,phi) -- Eq (7)
for (int itheta = 0; itheta < INSCATTER_SPHERICAL_INTEGRAL_SAMPLES; ++itheta) {
float theta = (float(itheta) + 0.5) * dtheta;
float ctheta = cos(theta);
float greflectance = 0.0;
float dground = 0.0;
vec3 gtransp = vec3(0.0);
if (ctheta < cthetamin) { // if ground visible in direction w
// compute transparency gtransp between x and ground
greflectance = AVERAGE_GROUND_REFLECTANCE / M_PI;
dground = -r * ctheta - ieeesqrt(r * r * (ctheta * ctheta - 1.0) + Rg * Rg);
gtransp = transmittance(Rg, -(r * ctheta + dground) / Rg, dground);
}
for (int iphi = 0; iphi < 2 * INSCATTER_SPHERICAL_INTEGRAL_SAMPLES; ++iphi) {
float phi = (float(iphi) + 0.5) * dphi;
float dw = dtheta * dphi * sin(theta);
vec3 w = vec3(cos(phi) * sin(theta), sin(phi) * sin(theta), ctheta);
float nu1 = dot(s, w);
float nu2 = dot(v, w);
float pr2 = phaseFunctionR(nu2);
float pm2 = phaseFunctionM(nu2);
// compute irradiance received at ground in direction w (if ground visible) =deltaE
vec3 gnormal = (vec3(0.0, 0.0, r) + dground * w) / Rg;
vec3 girradiance = irradiance(deltaESampler, Rg, dot(gnormal, s));
vec3 raymie1; // light arriving at x from direction w
// first term = light reflected from the ground and attenuated before reaching x, =T.alpha/PI.deltaE
raymie1 = greflectance * girradiance * gtransp;
// second term = inscattered light, =deltaS
if (first == 1.0) {
// first iteration is special because Rayleigh and Mie were stored separately,
// without the phase functions factors; they must be reintroduced here
float pr1 = phaseFunctionR(nu1);
float pm1 = phaseFunctionM(nu1);
vec3 ray1 = texture4D(deltaSRSampler, r, w.z, muS, nu1).rgb;
vec3 mie1 = texture4D(deltaSMSampler, r, w.z, muS, nu1).rgb;
raymie1 += ray1 * pr1 + mie1 * pm1;
} else {
raymie1 += texture4D(deltaSRSampler, r, w.z, muS, nu1).rgb;
}
// light coming from direction w and scattered in direction v
// = light arriving at x from direction w (raymie1) * SUM(scattering coefficient * phaseFunction)
// see Eq (7)
raymie += raymie1 * (betaR * exp(-(r - Rg) / HR) * pr2 + betaMSca * exp(-(r - Rg) / HM) * pm2) * dw;
}
}
// output raymie = J[T.alpha/PI.deltaE + deltaS] (line 7 in algorithm 4.1)
}
void main() {
vec3 raymie;
float mu, muS, nu;
getMuMuSNu(r, dhdH, mu, muS, nu);
inscatter(r, mu, muS, nu, raymie);
gl_FragColor.rgb = raymie;
}
#endif
|
