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