// -*-C++-*- // written by Thorsten Renk, Oct 2011, based on default.frag // Ambient term comes in gl_Color.rgb. varying vec4 diffuse_term; varying vec3 normal; varying vec3 relPos; uniform sampler2D texture; varying float yprime_alt; varying float mie_angle; uniform float visibility; uniform float avisibility; uniform float scattering; uniform float terminator; uniform float terrain_alt; uniform float hazeLayerAltitude; uniform float overcast; uniform float eye_alt; uniform float cloud_self_shading; const float EarthRadius = 5800000.0; const float terminator_width = 200000.0; float alt; float eShade; float fog_func (in float targ, in float alt); vec3 get_hazeColor(in float light_arg); float luminance(vec3 color) { return dot(vec3(0.212671, 0.715160, 0.072169), color); } void main() { vec3 shadedFogColor = vec3(0.55, 0.67, 0.88); // this is taken from default.frag vec3 n; float NdotL, NdotHV, fogFactor; vec4 color = gl_Color; vec3 lightDir = gl_LightSource[0].position.xyz; vec3 halfVector = gl_LightSource[0].halfVector.xyz; vec4 texel; vec4 fragColor; vec4 specular = vec4(0.0); float intensity; float effective_scattering = min(scattering, cloud_self_shading); vec4 light_specular = gl_LightSource[0].specular; // If gl_Color.a == 0, this is a back-facing polygon and the // normal should be reversed. n = (2.0 * gl_Color.a - 1.0) * normal; n = normalize(n); NdotL = dot(n, lightDir); if (NdotL > 0.0) { color += diffuse_term * NdotL; NdotHV = max(dot(n, halfVector), 0.0); if (gl_FrontMaterial.shininess > 0.0) specular.rgb = (gl_FrontMaterial.specular.rgb * light_specular.rgb * pow(NdotHV, gl_FrontMaterial.shininess)); } color.a = diffuse_term.a; // This shouldn't be necessary, but our lighting becomes very // saturated. Clamping the color before modulating by the texture // is closer to what the OpenGL fixed function pipeline does. color = clamp(color, 0.0, 1.0); texel = texture2D(texture, gl_TexCoord[0].st); fragColor = color * texel + specular; // here comes the terrain haze model float delta_z = hazeLayerAltitude - eye_alt; float dist = length(relPos); float mvisibility = min(visibility,avisibility); if (dist > 0.04 * mvisibility) { alt = eye_alt; float transmission; float vAltitude; float delta_zv; float H; float distance_in_layer; float transmission_arg; // angle with horizon float ct = dot(vec3(0.0, 0.0, 1.0), relPos)/dist; // we solve the geometry what part of the light path is attenuated normally and what is through the haze layer if (delta_z > 0.0) // we're inside the layer { if (ct < 0.0) // we look down { distance_in_layer = dist; vAltitude = min(distance_in_layer,mvisibility) * ct; delta_zv = delta_z - vAltitude; } else // we may look through upper layer edge { H = dist * ct; if (H > delta_z) {distance_in_layer = dist/H * delta_z;} else {distance_in_layer = dist;} vAltitude = min(distance_in_layer,visibility) * ct; delta_zv = delta_z - vAltitude; } } else // we see the layer from above, delta_z < 0.0 { H = dist * -ct; if (H < (-delta_z)) // we don't see into the layer at all, aloft visibility is the only fading { distance_in_layer = 0.0; delta_zv = 0.0; } else { vAltitude = H + delta_z; distance_in_layer = vAltitude/H * dist; vAltitude = min(distance_in_layer,visibility) * (-ct); delta_zv = vAltitude; } } // ground haze cannot be thinner than aloft visibility in the model, // so we need to use aloft visibility otherwise transmission_arg = (dist-distance_in_layer)/avisibility; float eqColorFactor; if (visibility < avisibility) { transmission_arg = transmission_arg + (distance_in_layer/visibility); // this combines the Weber-Fechner intensity eqColorFactor = 1.0 - 0.1 * delta_zv/visibility - (1.0 -effective_scattering); } else { transmission_arg = transmission_arg + (distance_in_layer/avisibility); // this combines the Weber-Fechner intensity eqColorFactor = 1.0 - 0.1 * delta_zv/avisibility - (1.0 -effective_scattering); } transmission = fog_func(transmission_arg, alt); // there's always residual intensity, we should never be driven to zero if (eqColorFactor < 0.2) {eqColorFactor = 0.2;} float lightArg = (terminator-yprime_alt)/100000.0; vec3 hazeColor = get_hazeColor(lightArg); // now dim the light for haze eShade = 1.0 - 0.9 * smoothstep(-terminator_width+ terminator, terminator_width + terminator, yprime_alt); // Mie-like factor if (lightArg < 10.0) {intensity = length(hazeColor); float mie_magnitude = 0.5 * smoothstep(350000.0, 150000.0, terminator-sqrt(2.0 * EarthRadius * terrain_alt)); 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)) ); } // high altitude desaturation of the haze color intensity = length(hazeColor); hazeColor = intensity * normalize (mix(hazeColor, intensity * vec3 (1.0,1.0,1.0), 0.7* smoothstep(5000.0, 50000.0, alt))); // blue hue of haze hazeColor.x = hazeColor.x * 0.83; hazeColor.y = hazeColor.y * 0.9; // additional blue in indirect light float fade_out = max(0.65 - 0.3 *overcast, 0.45); intensity = length(hazeColor); hazeColor = intensity * normalize(mix(hazeColor, 1.5* shadedFogColor, 1.0 -smoothstep(0.25, fade_out,eShade) )); // change haze color to blue hue for strong fogging //intensity = length(hazeColor); hazeColor = intensity * normalize(mix(hazeColor, shadedFogColor, (1.0-smoothstep(0.5,0.9,eqColorFactor)))); // reduce haze intensity when looking at shaded surfaces, only in terminator region float shadow = mix( min(1.0 + dot(normal,lightDir),1.0), 1.0, 1.0-smoothstep(0.1, 0.4, transmission)); hazeColor = mix(shadow * hazeColor, hazeColor, 0.3 + 0.7* smoothstep(250000.0, 400000.0, terminator)); // don't let the light fade out too rapidly lightArg = (terminator + 200000.0)/100000.0; float minLightIntensity = min(0.2,0.16 * lightArg + 0.5); vec3 minLight = minLightIntensity * vec3 (0.2, 0.3, 0.4); hazeColor *= eqColorFactor * eShade; hazeColor.rgb = max(hazeColor.rgb, minLight.rgb); // determine the right mix of transmission and haze fragColor.rgb = mix(hazeColor, fragColor.rgb,transmission); } gl_FragColor = fragColor; }