198 lines
5.3 KiB
GLSL
198 lines
5.3 KiB
GLSL
#version 120
|
|
|
|
// Atmospheric scattering shader for flightgear
|
|
// Written by Lauri Peltonen (Zan)
|
|
// Implementation of O'Neil's algorithm
|
|
|
|
varying vec3 rayleigh;
|
|
varying vec3 mie;
|
|
varying vec3 eye;
|
|
varying vec3 hazeColor;
|
|
varying float ct;
|
|
//varying float cosphi;
|
|
varying float delta_z;
|
|
varying float alt;
|
|
varying float earthShade;
|
|
|
|
uniform float overcast;
|
|
uniform float saturation;
|
|
uniform float visibility;
|
|
uniform float avisibility;
|
|
uniform float scattering;
|
|
|
|
const float EarthRadius = 5800000.0;
|
|
|
|
float miePhase(in float cosTheta, in float g)
|
|
{
|
|
float g2 = g*g;
|
|
float a = 1.5 * (1.0 - g2);
|
|
float b = (2.0 + g2);
|
|
float c = 1.0 + cosTheta*cosTheta;
|
|
float d = pow(1.0 + g2 - 2.0 * g * cosTheta, 0.6667);
|
|
|
|
return (a*c) / (b*d);
|
|
}
|
|
|
|
float rayleighPhase(in float cosTheta)
|
|
{
|
|
//return 1.5 * (1.0 + cosTheta*cosTheta);
|
|
return 1.5 * (2.0 + 0.5*cosTheta*cosTheta);
|
|
}
|
|
|
|
|
|
|
|
void main()
|
|
{
|
|
float cosTheta = dot(normalize(eye), gl_LightSource[0].position.xyz);
|
|
|
|
// position of the horizon line
|
|
|
|
float lAltitude = alt + delta_z;
|
|
float radiusEye = EarthRadius + alt;
|
|
float radiusLayer = EarthRadius + lAltitude;
|
|
float cthorizon;
|
|
float ctterrain;
|
|
|
|
if (radiusEye > radiusLayer) cthorizon = -sqrt(radiusEye * radiusEye - radiusLayer * radiusLayer)/radiusEye;
|
|
else cthorizon = sqrt(radiusLayer * radiusLayer - radiusEye * radiusEye)/radiusLayer;
|
|
|
|
ctterrain = -sqrt(radiusEye * radiusEye - EarthRadius * EarthRadius)/radiusEye;
|
|
|
|
vec3 color = rayleigh * rayleighPhase(cosTheta);
|
|
color += mie * miePhase(cosTheta, -0.8);
|
|
|
|
vec3 black = vec3(0.0,0.0,0.0);
|
|
|
|
|
|
float ovc = overcast;
|
|
|
|
|
|
|
|
float sat = 1.0 - ((1.0 - saturation) * 2.0);
|
|
if (sat < 0.3) sat = 0.3;
|
|
|
|
|
|
// float wscale = 1.732;
|
|
|
|
// an overexposure filter, the log() seems to be pretty expensive though
|
|
|
|
// if (color.x > 0.8) color.x = 0.8 + 0.8* log(color.x/0.8);
|
|
// if (color.y > 0.8) color.y = 0.8 + 0.8* log(color.y/0.8);
|
|
// if (color.z > 0.8) color.z = 0.8 + 0.8* log(color.z/0.8);
|
|
|
|
//vec3 fogColor = vec3 (gl_Fog.color.x, gl_Fog.color.y, gl_Fog.color.z);
|
|
|
|
|
|
// reduce the whiteout near the horizon generated by the single scattering approximation
|
|
|
|
if (ct > cthorizon) color = mix(color, black ,smoothstep(0.2+cthorizon, -0.2+cthorizon, ct));
|
|
else color = mix (color, black, smoothstep(0.2+cthorizon,-0.2+cthorizon, cthorizon));
|
|
|
|
|
|
|
|
|
|
// fog computations for a ground haze layer, extending from zero to lAltitude
|
|
|
|
|
|
|
|
float transmission;
|
|
float vAltitude;
|
|
float delta_zv;
|
|
|
|
float costheta = ct;
|
|
|
|
float vis= visibility;
|
|
|
|
// hack - in an effect volume the visibility only may be reduced, so we take care here
|
|
if (avisibility < visibility){vis = avisibility;}
|
|
|
|
if (delta_z > 0.0) // we're inside the layer
|
|
{
|
|
if (costheta>0.0 + ctterrain) // looking up, view ray intersecting upper layer edge
|
|
{
|
|
transmission = exp(-min((delta_z/max(costheta,0.1)),25000.0)/vis);
|
|
//transmission = 1.0;
|
|
vAltitude = min(vis * costheta, delta_z);
|
|
delta_zv = delta_z - vAltitude;
|
|
}
|
|
|
|
else // looking down, view range intersecting terrain (which may not be drawn)
|
|
{
|
|
transmission = exp(alt/vis/costheta);
|
|
vAltitude = min(-vis * costheta, alt);
|
|
delta_zv = delta_z + vAltitude;
|
|
}
|
|
}
|
|
else // we see the layer from above
|
|
{
|
|
if (costheta < 0.0 + cthorizon)
|
|
{
|
|
transmission = exp(-min(lAltitude/abs(costheta),25000.0)/vis);
|
|
transmission = transmission * exp(-alt/avisibility/abs(costheta));
|
|
transmission = 1.0 - (1.0 - transmission) * smoothstep(0+cthorizon, -0.02+cthorizon, costheta);
|
|
vAltitude = min(lAltitude, -vis * costheta);
|
|
delta_zv = vAltitude;
|
|
}
|
|
else
|
|
{
|
|
transmission = 1.0;
|
|
delta_zv = 0.0;
|
|
}
|
|
}
|
|
|
|
// combined intensity reduction by cloud shading and fog self-shading, corrected for Weber-Fechner perception law
|
|
|
|
float eqColorFactor;
|
|
eqColorFactor = 1.0 - 0.1 * delta_zv/vis - (1.0 -scattering);
|
|
|
|
|
|
|
|
|
|
|
|
// there's always residual intensity, we should never be driven to zero
|
|
if (eqColorFactor < 0.2) eqColorFactor = 0.2;
|
|
|
|
|
|
// postprocessing of haze color
|
|
vec3 hColor = hazeColor;
|
|
|
|
// high altitude desaturation
|
|
float intensity = length(hColor);
|
|
hColor = intensity * normalize (mix(hColor, intensity * vec3 (1.0,1.0,1.0), 0.7* smoothstep(5000.0, 50000.0, alt)));
|
|
|
|
// blue hue
|
|
hColor.x = 0.83 * hColor.x;
|
|
hColor.y = 0.9 * hColor.y;
|
|
|
|
|
|
|
|
// further blueshift when in shadow, either cloud shadow, or self-shadow or Earth shadow, dependent on indirect
|
|
// light
|
|
|
|
float fade_out = max(0.65 - 0.3 *overcast, 0.45);
|
|
intensity = length(hColor);
|
|
hColor = intensity * normalize(mix(hColor, 1.5* vec3 (0.45, 0.6, 0.8), 1.0 -smoothstep(0.25, fade_out,earthShade) ));
|
|
hColor = intensity * normalize(mix(hColor, 2.0 * vec3 (0.55, 0.6, 0.8), (1.0 - smoothstep(0.3,0.8,eqColorFactor))));
|
|
hColor = hColor * earthShade;
|
|
|
|
// accounting for overcast and saturation
|
|
|
|
|
|
color = ovc * mix(color, hazeColor * earthShade ,smoothstep(-0.1+ctterrain, 0.0+ctterrain, ct)) + (1-ovc) * color;
|
|
color = sat * color + (1.0 - sat) * mix(color, black, smoothstep(0.4+cthorizon,0.2+cthorizon,ct));
|
|
|
|
|
|
// the terrain below the horizon gets drawn in one optical thickness
|
|
vec3 terrainHazeColor = eqColorFactor * hColor;
|
|
color = mix(color, terrainHazeColor ,smoothstep(0.01 + ctterrain, 0.0+ctterrain, ct));
|
|
|
|
// mix fog the skydome with the right amount of haze
|
|
|
|
color = transmission * color + (1.0-transmission) * eqColorFactor * hColor;
|
|
|
|
|
|
gl_FragColor = vec4(color, 1.0);
|
|
gl_FragDepth = 0.1;
|
|
|
|
}
|
|
|