1// -*-C++-*-
2#version 120
3
4varying float fogFactor;
5varying vec3 hazeColor;
6varying float mie_frag;
7varying float mie_frag_mod;
8varying vec3 internal_pos;
9varying float bottom_shade;
10varying float z_pos;
11
12varying float flogz;
13
14uniform float range; // From /sim/rendering/clouds3d-vis-range
15uniform float detail_range; // From /sim/rendering/clouds3d_detail-range
16uniform float scattering;
17uniform float terminator;
18uniform float altitude;
19uniform float cloud_self_shading;
20uniform float visibility;
21uniform float moonlight;
22uniform float air_pollution;
23uniform float flash;
24uniform float lightning_pos_x;
25uniform float lightning_pos_y;
26uniform float lightning_range;
27
28attribute vec3 usrAttr1;
29attribute vec3 usrAttr2;
30
31float alpha_factor = usrAttr1.r;
32float shade_factor = usrAttr1.g;
33float cloud_height = usrAttr1.b;
34float bottom_factor = usrAttr2.r;
35float middle_factor = usrAttr2.g;
36float top_factor = usrAttr2.b;
37
38const float EarthRadius = 5800000.0;
39
40// light_func is a generalized logistic function fit to the light intensity as a function
41// of scaled terminator position obtained from Flightgear core
42
43float light_func (in float x, in float a, in float b, in float c, in float d, in float e)
44{
45x = x-0.5;
46
47
48// use the asymptotics to shorten computations
49if (x > 30.0) {return e;}
50if (x < -15.0) {return 0.03;}
51
52
53return e / pow((1.0 + a * exp(-b * (x-c)) ),(1.0/d));
54}
55
56
57float mie_func (in float x, in float Mie)
58{
59return x + 2.0 * x * Mie * (1.0 -0.8*x) * (1.0 -0.8*x);
60}
61
62void main(void)
63{
64
65
66  //shade_factor = shade_factor * cloud_self_shading;
67  //top_factor = top_factor * cloud_self_shading;
68  //shade_factor = min(shade_factor, top_factor);
69  //middle_factor = min(middle_factor, top_factor);
70  //bottom_factor = min(bottom_factor, top_factor);
71
72  float intensity;
73  float mix_factor;
74
75  bottom_shade = bottom_factor;
76
77  vec3 shadedFogColor = vec3(0.55, 0.67, 0.88);
78  vec3 moonLightColor = vec3 (0.095, 0.095, 0.15) * moonlight * scattering;
79  gl_TexCoord[0] = gl_MultiTexCoord0;
80  vec4 ep = gl_ModelViewMatrixInverse * vec4(0.0,0.0,0.0,1.0);
81  vec4 l  = gl_ModelViewMatrixInverse * vec4(0.0,0.0,1.0,1.0);
82  vec3 u = normalize(ep.xyz - l.xyz);
83
84  // Find a rotation matrix that rotates 1,0,0 into u. u, r and w are
85  // the columns of that matrix.
86  vec3 absu = abs(u);
87  vec3 r = normalize(vec3(-u.y, u.x, 0.0));
88  vec3 w = cross(u, r);
89
90  // Do the matrix multiplication by [ u r w pos]. Assume no
91  // scaling in the homogeneous component of pos.
92  gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
93  gl_Position.xyz = gl_Vertex.x * u;
94  gl_Position.xyz += gl_Vertex.y * r;
95  gl_Position.xyz += gl_Vertex.z * w;
96  // Apply Z scaling to allow sprites to be squashed in the z-axis
97  gl_Position.z = gl_Position.z * gl_Color.w;
98
99  // Now shift the sprite to the correct position in the cloud.
100  gl_Position.xyz += gl_Color.xyz;
101
102  internal_pos = gl_Position.xyz/ cloud_height;
103
104
105  // Determine a lighting normal based on the vertex position from the
106  // center of the cloud, so that sprite on the opposite side of the cloud to the sun are darker.
107  float n = dot(normalize(-gl_LightSource[0].position.xyz),
108                normalize(vec3(gl_ModelViewMatrix * vec4(- gl_Position.x, - gl_Position.y, - gl_Position.z, 0.0))));
109
110  // prepare suppression of shadeward Mie terms
111  float n1 = dot(normalize(-gl_LightSource[0].position.xyz),
112                normalize(vec3(gl_ModelViewMatrix * vec4(- gl_Color.x, - gl_Color.y, - gl_Color.z, 0.0))));
113
114  //z_pos = dot(normalize(-gl_LightSource[0].position.xyz),
115   //             vec3(gl_ModelViewMatrix * vec4(- gl_Position.x, - gl_Position.y, - gl_Position.z, 0.0)))/cloud_height;
116
117
118  float mie_suppress = smoothstep(0.0, 0.3, n1);
119
120  // Determine the position - used for fog and shading calculations
121  float fogCoord = length(vec3(gl_ModelViewMatrix * vec4(gl_Color.x, gl_Color.y, gl_Color.z, 1.0)));
122  float center_dist = length(vec3(gl_ModelViewMatrix * vec4(0.0,0.0,0.0,1.0)));
123
124  z_pos = (fogCoord - center_dist)/cloud_height;
125
126  if ((fogCoord > detail_range) && (fogCoord > center_dist) && (shade_factor < 0.7)) {
127    // More than detail_range away, so discard all sprites on opposite side of
128    // cloud center by shifting them beyond the view fustrum
129    gl_Position = vec4(0.0,0.0,10.0,1.0);
130    gl_FrontColor.a = 0.0;
131  } else {
132
133    // Determine the shading of the vertex. We shade it based on it's position
134    // in the cloud relative to the sun, and it's vertical position in the cloud.
135    float shade = mix(shade_factor, top_factor,  smoothstep(-0.3, 0.3, n));
136    //if (n < 0) {
137    //  shade = mix(top_factor, shade_factor, abs(n));
138    //}
139
140    if (gl_Position.z < 0.5 * cloud_height) {
141      shade = min(shade, mix(bottom_factor, middle_factor, gl_Position.z * 2.0 / cloud_height));
142    } else {
143      shade = min(shade, mix(middle_factor, top_factor, gl_Position.z * 2.0 / cloud_height - 1.0));
144    }
145
146    //float h = gl_Position.z / cloud_height;
147    //if (h < 0.5) {
148    //  shade = min(shade, mix(bottom_factor, middle_factor, smoothstep(0.0, 0.5, h)));
149    //} else {
150    //  shade = min(shade, mix(middle_factor, top_factor, smoothstep(2.0 * (h - 0.5)));
151   // }
152
153    // Final position of the sprite
154    vec3 relVector = gl_Position.xyz - ep.xyz;
155    gl_Position = gl_ModelViewProjectionMatrix * gl_Position;
156    // logarithmic depth
157    flogz = 1.0 + gl_Position.w;
158
159   // Light at the final position
160
161   // first obtain normal to sun position
162
163    vec3 lightFull = (gl_ModelViewMatrixInverse * gl_LightSource[0].position).xyz;
164    vec3 lightHorizon = normalize(vec3(lightFull.x,lightFull.y, 0.0));
165
166
167
168   // yprime is the distance of the vertex into sun direction, corrected for altitude
169   // the altitude correction is clamped to reasonable values, sometimes altitude isn't parsed correctly, leading
170   // to overbright or overdark clouds
171   // float vertex_alt = clamp(altitude * 0.30480 + relVector.z,1000.0,10000.0);
172    float vertex_alt = clamp(altitude + relVector.z, 300.0, 10000.0);
173    float yprime = -dot(relVector, lightHorizon);
174    float yprime_alt = yprime -sqrt(2.0 * EarthRadius * vertex_alt);
175
176   // two times terminator width governs how quickly light fades into shadow
177    float terminator_width = 200000.0;
178    float earthShade = 1.0- 0.9*  smoothstep(-terminator_width+ terminator, terminator_width + terminator, yprime_alt);
179    float earthShadeFactor = 1.0 - smoothstep(0.4, 0.5, earthShade);
180
181    // compute the light at the position
182    vec4 light_diffuse;
183
184    float lightArg = (terminator-yprime_alt)/100000.0;
185
186    light_diffuse.b = light_func(lightArg -1.2 * air_pollution, 1.330e-05, 0.264, 2.227, 1.08e-05, 1.0);
187    light_diffuse.g = light_func(lightArg -0.6 * air_pollution, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
188    light_diffuse.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
189    light_diffuse.a = 1.0;
190
191    //light_diffuse *= cloud_self_shading;
192    intensity = (1.0 - (0.8 * (1.0 - earthShade))) *  length(light_diffuse.rgb);
193    light_diffuse.rgb = intensity * normalize(mix(light_diffuse.rgb, shadedFogColor, (1.0 - smoothstep(0.5,0.9, min(scattering, cloud_self_shading)  ))));
194
195    // correct ambient light intensity and hue before sunrise
196    if (earthShade < 0.6)
197    {
198    light_diffuse.rgb = intensity * normalize(mix(light_diffuse.rgb,  shadedFogColor, 1.0 -smoothstep(0.1, 0.6,earthShade ) ));
199
200    }
201
202
203
204    gl_FrontColor.rgb = intensity * shade * normalize(mix(light_diffuse.rgb, shadedFogColor, smoothstep(0.1,0.4, (1.0 - shade)  ))) ;
205
206    // lightning
207    vec2 lightningRelVector = relVector.xy - vec2(lightning_pos_x, lightning_pos_y);
208    float rCoord = length(lightningRelVector);
209
210    vec3 flash_color = vec3 (0.43, 0.57, 1.0);
211    float flash_factor = flash;
212
213    if (flash == 2)
214	{
215	flash_color = vec3 (0.8, 0.7, 0.4);
216	flash_factor = 1;
217	}
218
219    float rn = 0.5 + 0.5 * fract(gl_Color.x);
220    gl_FrontColor.rgb += flash_factor * flash_color  * (1.0 - smoothstep(lightning_range, 5.0 * lightning_range, rCoord)) * rn;
221
222
223    // fading of cloudlets
224
225    if ((fogCoord > (0.9 * detail_range)) && (fogCoord > center_dist) && (shade_factor < 0.7)) {
226      // cloudlet is almost at the detail range, so fade it out.
227      gl_FrontColor.a = 1.0 - smoothstep(0.9 * detail_range, detail_range, fogCoord);
228    } else {
229      // As we get within 100m of the sprite, it is faded out. Equally at large distances it also fades out.
230      gl_FrontColor.a = min(smoothstep(10.0, 100.0, fogCoord), 1.0 - smoothstep(0.9 * range, range, fogCoord));
231    }
232    gl_FrontColor.a = gl_FrontColor.a * (1.0 - smoothstep(visibility, 3.0* visibility, fogCoord));
233
234    fogFactor = exp(-fogCoord/visibility);
235
236    // haze of ground haze shader is slightly bluish
237    hazeColor = light_diffuse.rgb;
238    hazeColor.r = hazeColor.r * 0.83;
239    hazeColor.g = hazeColor.g * 0.9;
240    hazeColor = hazeColor * scattering;
241
242
243    // Mie correction
244    float Mie = 0.0;
245    float MieFactor =   dot(normalize(lightFull), normalize(relVector));
246
247
248    mie_frag = MieFactor;
249    mie_frag_mod =  mie_suppress * (1.0 - smoothstep(0.4, 0.6, bottom_factor)) * (1.0 - smoothstep(detail_range, 1.5 * detail_range, fogCoord)) * smoothstep(0.65, 0.8, scattering)
250	   * smoothstep(0.7, 1.0, top_factor);
251
252
253    if (bottom_factor < 0.4) {mie_frag_mod = 0.0;}
254
255     if (bottom_factor > 0.4)
256    {
257    MieFactor =   dot(normalize(lightFull), normalize(relVector));
258    Mie = 1.5 * smoothstep(0.9,1.0, MieFactor) * smoothstep(0.6, 0.8, bottom_factor) * (1.0-earthShadeFactor) ;
259   //if (MieFactor < 0.0) {Mie = - Mie;}
260    }
261     //else {Mie = 0.0;}
262
263     if (Mie > 0.0)
264      {
265    hazeColor.r = mie_func(hazeColor.r, Mie);
266    hazeColor.g = mie_func(hazeColor.g, 0.8* Mie);
267    hazeColor.b = mie_func(hazeColor.b, 0.5* Mie);
268
269    gl_FrontColor.r = mie_func(gl_FrontColor.r, Mie);
270    gl_FrontColor.g = mie_func(gl_FrontColor.g, 0.8* Mie);
271    gl_FrontColor.b = mie_func(gl_FrontColor.b, 0.5*Mie);
272    }
273     else if (MieFactor < 0.0)
274     {
275    float thickness_reduction = smoothstep(0.4, 0.8, bottom_factor) ;
276    float light_reduction = dot (lightFull, lightHorizon);
277    light_reduction *= light_reduction;
278
279    float factor_b = 0.8 + 0.2 * (1.0 - smoothstep(0.0, 0.7, -MieFactor) * thickness_reduction * light_reduction) ;
280    float factor_r = 0.6 + 0.4 * (1.0 - smoothstep(0.0, 0.7, -MieFactor) * thickness_reduction * light_reduction) ;
281    float factor_g = 0.65 + 0.35 * (1.0 - smoothstep(0.0, 0.7, -MieFactor) * thickness_reduction * light_reduction) ;
282    hazeColor.r *= factor_r;
283    hazeColor.g *= factor_g;
284    hazeColor.b *= factor_b;
285
286    gl_FrontColor.r *= factor_r;
287    gl_FrontColor.g *= factor_g;
288    gl_FrontColor.b *= factor_b;
289     }
290
291    gl_FrontColor.rgb = gl_FrontColor.rgb +  moonLightColor * earthShadeFactor;
292    hazeColor.rgb = hazeColor.rgb + moonLightColor * earthShadeFactor;
293    gl_FrontColor.a = gl_FrontColor.a * alpha_factor;
294    gl_BackColor = gl_FrontColor;
295  }
296}
297