120 lines
2.7 KiB
C++
120 lines
2.7 KiB
C++
// -*-C++-*-
|
|
|
|
uniform sampler2D texture;
|
|
|
|
uniform float visibility;
|
|
uniform float avisibility;
|
|
uniform float hazeLayerAltitude;
|
|
uniform float eye_alt;
|
|
|
|
varying vec3 relPos;
|
|
varying float pixelSize;
|
|
|
|
float alt;
|
|
|
|
|
|
float fog_func (in float targ)
|
|
{
|
|
|
|
|
|
float fade_mix;
|
|
|
|
// for large altitude > 30 km, we switch to some component of quadratic distance fading to
|
|
// create the illusion of improved visibility range
|
|
|
|
targ = 1.25 * targ * smoothstep(0.04,0.06,targ); // need to sync with the distance to which terrain is drawn
|
|
|
|
|
|
if (alt < 30000.0)
|
|
{return exp(-targ - targ * targ * targ * targ);}
|
|
else if (alt < 50000.0)
|
|
{
|
|
fade_mix = (alt - 30000.0)/20000.0;
|
|
return fade_mix * exp(-targ*targ - pow(targ,4.0)) + (1.0 - fade_mix) * exp(-targ - pow(targ,4.0));
|
|
}
|
|
else
|
|
{
|
|
return exp(- targ * targ - pow(targ,4.0));
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
void main()
|
|
{
|
|
|
|
float dist = length(relPos);
|
|
float delta_z = hazeLayerAltitude - 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,min(visibility, avisibility)) * 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;
|
|
if (visibility < avisibility)
|
|
{
|
|
transmission_arg = transmission_arg + (distance_in_layer/visibility);
|
|
}
|
|
else
|
|
{
|
|
transmission_arg = transmission_arg + (distance_in_layer/avisibility);
|
|
}
|
|
|
|
|
|
|
|
transmission = fog_func(transmission_arg);
|
|
float dist_att = exp(-0.3/pixelSize);
|
|
|
|
vec4 texel = texture2D(texture,gl_TexCoord[0].st);
|
|
gl_FragColor = vec4 (gl_Color.rgb, texel.a * transmission * dist_att);
|
|
|
|
|
|
}
|