351 lines
8.6 KiB
C++
351 lines
8.6 KiB
C++
// -*-C++-*-
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// written by Thorsten Renk, Oct 2011, based on default.frag
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varying vec3 relPos;
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uniform sampler2D texture;
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varying float yprime_alt;
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uniform float visibility;
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uniform float avisibility;
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uniform float scattering;
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uniform float cloud_self_shading;
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uniform float terminator;
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uniform float terrain_alt;
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uniform float hazeLayerAltitude;
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uniform float overcast;
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uniform float eye_alt;
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uniform float dust_cover_factor;
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uniform float landing_light1_offset;
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uniform float landing_light2_offset;
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uniform int use_searchlight;
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uniform int use_landing_light;
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uniform int use_alt_landing_light;
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uniform int quality_level;
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uniform int tquality_level;
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const float EarthRadius = 5800000.0;
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const float terminator_width = 200000.0;
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float alt;
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float mie_angle;
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float light_distance_fading(in float dist);
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float fog_backscatter(in float avisibility);
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vec3 searchlight();
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vec3 landing_light(in float offset);
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float luminance(vec3 color)
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{
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return dot(vec3(0.212671, 0.715160, 0.072169), color);
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}
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float light_func (in float x, in float a, in float b, in float c, in float d, in float e)
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{
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x = x - 0.5;
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// use the asymptotics to shorten computations
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if (x > 30.0) {return e;}
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if (x < -15.0) {return 0.0;}
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return e / pow((1.0 + a * exp(-b * (x-c)) ),(1.0/d));
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}
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// this determines how light is attenuated in the distance
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// physically this should be exp(-arg) but for technical reasons we use a sharper cutoff
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// for distance > visibility
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float fog_func (in float targ)
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{
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float fade_mix;
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// for large altitude > 30 km, we switch to some component of quadratic distance fading to
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// create the illusion of improved visibility range
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targ = 1.25 * targ * smoothstep(0.07,0.1,targ); // need to sync with the distance to which terrain is drawn
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if (alt < 30000.0)
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{return exp(-targ - targ * targ * targ * targ);}
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else if (alt < 50000.0)
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{
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fade_mix = (alt - 30000.0)/20000.0;
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return fade_mix * exp(-targ*targ - pow(targ,4.0)) + (1.0 - fade_mix) * exp(-targ - pow(targ,4.0));
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}
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else
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{
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return exp(- targ * targ - pow(targ,4.0));
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}
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}
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float rand2D(in vec2 co){
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return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
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}
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float simple_interpolate(in float a, in float b, in float x)
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{
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return a + smoothstep(0.0,1.0,x) * (b-a);
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}
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float interpolatedNoise2D(in float x, in float y)
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{
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float integer_x = x - fract(x);
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float fractional_x = x - integer_x;
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float integer_y = y - fract(y);
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float fractional_y = y - integer_y;
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float v1 = rand2D(vec2(integer_x, integer_y));
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float v2 = rand2D(vec2(integer_x+1.0, integer_y));
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float v3 = rand2D(vec2(integer_x, integer_y+1.0));
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float v4 = rand2D(vec2(integer_x+1.0, integer_y +1.0));
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float i1 = simple_interpolate(v1 , v2 , fractional_x);
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float i2 = simple_interpolate(v3 , v4 , fractional_x);
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return simple_interpolate(i1 , i2 , fractional_y);
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}
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float Noise2D(in vec2 coord, in float wavelength)
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{
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return interpolatedNoise2D(coord.x/wavelength, coord.y/wavelength);
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}
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void main()
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{
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vec3 shadedFogColor = vec3(0.65, 0.67, 0.78);
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vec3 lightDir = gl_LightSource[0].position.xyz;
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float intensity;
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mie_angle = gl_Color.a;
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vec4 texel = texture2D(texture, gl_TexCoord[0].st);
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float effective_scattering = min(scattering, cloud_self_shading);
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float dist = length(relPos);
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if (quality_level > 3)
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{
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// mix dust
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vec4 dust_color = vec4 (0.76, 0.71, 0.56, texel.a);
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texel = mix(texel, dust_color, clamp(0.6 * dust_cover_factor ,0.0, 1.0) );
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}
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// ALS secondary light sources
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vec3 secondary_light = vec3 (0.0,0.0,0.0);
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if ((quality_level>5) && (tquality_level>5))
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{
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if (use_searchlight == 1)
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{
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secondary_light += searchlight();
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}
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if (use_landing_light == 1)
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{
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secondary_light += landing_light(landing_light1_offset);
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}
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if (use_alt_landing_light == 1)
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{
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secondary_light += landing_light(landing_light2_offset);
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}
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}
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vec4 fragColor = vec4 (gl_Color.rgb +secondary_light * light_distance_fading(dist),1.0) * texel;
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// here comes the terrain haze model
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float delta_z = hazeLayerAltitude - eye_alt;
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if (dist > max(40.0, 0.07 * min(visibility,avisibility)))
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//if (dist > 40.0)
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//if (0==1)
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{
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alt = eye_alt;
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float transmission;
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float vAltitude;
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float delta_zv;
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float H;
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float distance_in_layer;
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float transmission_arg;
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// angle with horizon
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float ct = dot(vec3(0.0, 0.0, 1.0), relPos)/dist;
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// we solve the geometry what part of the light path is attenuated normally and what is through the haze layer
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if (delta_z > 0.0) // we're inside the layer
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{
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if (ct < 0.0) // we look down
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{
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distance_in_layer = dist;
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vAltitude = min(distance_in_layer,min(visibility, avisibility)) * ct;
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delta_zv = delta_z - vAltitude;
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}
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else // we may look through upper layer edge
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{
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H = dist * ct;
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if (H > delta_z) {distance_in_layer = dist/H * delta_z;}
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else {distance_in_layer = dist;}
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vAltitude = min(distance_in_layer,visibility) * ct;
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delta_zv = delta_z - vAltitude;
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}
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}
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else // we see the layer from above, delta_z < 0.0
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{
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H = dist * -ct;
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if (H < (-delta_z)) // we don't see into the layer at all, aloft visibility is the only fading
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{
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distance_in_layer = 0.0;
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delta_zv = 0.0;
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}
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else
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{
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vAltitude = H + delta_z;
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distance_in_layer = vAltitude/H * dist;
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vAltitude = min(distance_in_layer,visibility) * (-ct);
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delta_zv = vAltitude;
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}
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}
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// blur of the haze layer edge
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float blur_thickness = 50.0;
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float cphi = dot(vec3(0.0, 1.0, 0.0), relPos)/dist;
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float ctlayer;
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float ctblur = 0.035 ;
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float blur_dist;
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if ((abs(delta_z) < 400.0)&&(quality_level>5)&&(tquality_level>5))
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{
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ctlayer = delta_z/dist-0.01 + 0.02 * Noise2D(vec2(cphi,1.0),0.1) -0.01;
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blur_dist = dist * (1.0-smoothstep(0.0,300.0,-delta_z)) * smoothstep(-400.0,-200.0, -delta_z);
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blur_dist = blur_dist * smoothstep(ctlayer-4.0*ctblur, ctlayer-ctblur, ct) * (1.0-smoothstep(ctlayer+0.5*ctblur, ctlayer+ctblur, ct));
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distance_in_layer = max(distance_in_layer, blur_dist);
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}
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// ground haze cannot be thinner than aloft visibility in the model,
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// so we need to use aloft visibility otherwise
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transmission_arg = (dist-distance_in_layer)/avisibility;
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float eqColorFactor;
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//float scattering = ground_scattering + (1.0 - ground_scattering) * smoothstep(hazeLayerAltitude -100.0, hazeLayerAltitude + 100.0, relPos.z + eye_alt);
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if (visibility < avisibility)
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{
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transmission_arg = transmission_arg + (distance_in_layer/visibility);
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// this combines the Weber-Fechner intensity
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eqColorFactor = 1.0 - 0.1 * delta_zv/visibility - (1.0 -effective_scattering);
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}
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else
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{
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transmission_arg = transmission_arg + (distance_in_layer/avisibility);
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// this combines the Weber-Fechner intensity
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eqColorFactor = 1.0 - 0.1 * delta_zv/avisibility - (1.0 -effective_scattering);
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}
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transmission = fog_func(transmission_arg);
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// there's always residual intensity, we should never be driven to zero
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if (eqColorFactor < 0.2) eqColorFactor = 0.2;
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float lightArg = (terminator-yprime_alt)/100000.0;
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vec3 hazeColor;
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hazeColor.b = light_func(lightArg, 1.330e-05, 0.264, 2.527, 1.08e-05, 1.0);
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hazeColor.g = light_func(lightArg, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
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hazeColor.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
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// now dim the light for haze
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//float eShade = earthShade;
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float eShade = 0.9 * smoothstep(terminator_width+ terminator, -terminator_width + terminator, yprime_alt) + 0.1;
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// Mie-like factor
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if (lightArg < 10.0)
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{intensity = length(hazeColor);
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float mie_magnitude = 0.5 * smoothstep(350000.0, 150000.0, terminator-sqrt(2.0 * EarthRadius * terrain_alt));
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hazeColor = intensity * ((1.0 - mie_magnitude) + mie_magnitude * mie_angle) * normalize(mix(hazeColor, vec3 (0.5, 0.58, 0.65), mie_magnitude * (0.5 - 0.5 * mie_angle)) );
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}
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// high altitude desaturation of the haze color
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intensity = length(hazeColor);
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hazeColor = intensity * normalize (mix(hazeColor, intensity * vec3 (1.0,1.0,1.0), 0.7* smoothstep(5000.0, 50000.0, alt)));
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// blue hue of haze
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hazeColor.x = hazeColor.x * 0.83;
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hazeColor.y = hazeColor.y * 0.9;
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// additional blue in indirect light
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float fade_out = max(0.65 - 0.3 *overcast, 0.45);
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intensity = length(hazeColor);
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hazeColor = intensity * normalize(mix(hazeColor, 1.5* shadedFogColor, 1.0 -smoothstep(0.25, fade_out,eShade) ));
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// change haze color to blue hue for strong fogging
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hazeColor = intensity * normalize(mix(hazeColor, shadedFogColor, (1.0-smoothstep(0.5,0.9,eqColorFactor))));
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// determine the right mix of transmission and haze
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hazeColor = clamp(hazeColor,0.0,1.0);
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fragColor.rgb = mix(eqColorFactor * hazeColor * eShade + secondary_light * fog_backscatter(avisibility), fragColor.rgb,transmission);
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gl_FragColor = fragColor;
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}
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else // if dist < 40.0 no fogging at all
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{
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gl_FragColor = fragColor;
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}
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}
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