// This shader is mostly an adaptation of the shader found at
// http://www.bonzaisoftware.com/water_tut.html and its glsl conversion
// available at http://forum.bonzaisoftware.com/viewthread.php?tid=10
// © Michael Horsch - 2005
// Major update and revisions - 2011-10-07
// © Emilian Huminiuc and Vivian Meazza
#version 120
varying vec4 waterTex1;
varying vec4 waterTex2;
varying vec4 waterTex4;
//varying vec4 ecPosition;
varying vec3 relPos;
varying vec3 specular_light;
varying vec3 viewerdir;
varying vec3 lightdir;
//varying vec3 normal;
varying float earthShade;
varying float yprime_alt;
varying float mie_angle;
uniform float osg_SimulationTime;
uniform float WindE, WindN;
uniform float hazeLayerAltitude;
uniform float terminator;
uniform float terrain_alt;
uniform float avisibility;
uniform float visibility;
uniform float overcast;
uniform float ground_scattering;
// This is the value used in the skydome scattering shader - use the same here for consistency?
const float EarthRadius = 5800000.0;
const float terminator_width = 200000.0;
float light_func (in float x, in float a, in float b, in float c, in float d, in float e)
{
//x = x - 0.5;
// use the asymptotics to shorten computations
if (x < -15.0) {return 0.0;}
return e / pow((1.0 + a * exp(-b * (x-c)) ),(1.0/d));
}
////fog "include"////////
// uniform int fogType;
//
// void fog_Func(int type);
/////////////////////////
/////// functions /////////
void rotationmatrix(in float angle, out mat4 rotmat)
{
rotmat = mat4( cos( angle ), -sin( angle ), 0.0, 0.0,
sin( angle ), cos( angle ), 0.0, 0.0,
0.0 , 0.0 , 1.0, 0.0,
0.0 , 0.0 , 0.0, 1.0 );
}
void main(void)
{
mat4 RotationMatrix;
// vec3 N = normalize(gl_Normal);
// normal = N;
vec4 ecPosition = gl_ModelViewMatrix * gl_Vertex;
viewerdir = vec3(gl_ModelViewMatrixInverse[3]) - vec3(gl_Vertex);
lightdir = normalize(vec3(gl_ModelViewMatrixInverse * gl_LightSource[0].position));
waterTex4 = vec4( ecPosition.xzy, 0.0 );
vec4 t1 = vec4(0.0, osg_SimulationTime * 0.005217, 0.0, 0.0);
vec4 t2 = vec4(0.0, osg_SimulationTime * -0.0012, 0.0, 0.0);
float Angle;
float windFactor = sqrt(WindE * WindE + WindN * WindN) * 0.05;
if (WindN == 0.0 && WindE == 0.0) {
Angle = 0.0;
}else{
Angle = atan(-WindN, WindE) - atan(1.0);
}
rotationmatrix(Angle, RotationMatrix);
waterTex1 = gl_MultiTexCoord0 * RotationMatrix - t1 * windFactor;
rotationmatrix(Angle, RotationMatrix);
waterTex2 = gl_MultiTexCoord0 * RotationMatrix - t2 * windFactor;
// fog_Func(fogType);
gl_Position = ftransform();
// here start computations for the haze layer
float yprime;
float lightArg;
float intensity;
float vertex_alt;
float scattering;
// we need several geometrical quantities
// first current altitude of eye position in model space
vec4 ep = gl_ModelViewMatrixInverse * vec4(0.0,0.0,0.0,1.0);
// and relative position to vector
relPos = gl_Vertex.xyz - ep.xyz;
// unfortunately, we need the distance in the vertex shader, although the more accurate version
// is later computed in the fragment shader again
float dist = length(relPos);
// altitude of the vertex in question, somehow zero leads to artefacts, so ensure it is at least 100m
vertex_alt = max(gl_Vertex.z,100.0);
scattering = 0.5 + 0.5 * ground_scattering + 0.5* (1.0 - ground_scattering) * smoothstep(hazeLayerAltitude -100.0, hazeLayerAltitude + 100.0, vertex_alt);
// branch dependent on daytime
if (terminator < 1000000.0) // the full, sunrise and sunset computation
{
// establish coordinates relative to sun position
//vec3 lightFull = (gl_ModelViewMatrixInverse * gl_LightSource[0].position).xyz;
//vec3 lightHorizon = normalize(vec3(lightFull.x,lightFull.y, 0.0));
vec3 lightHorizon = normalize(vec3(lightdir.x,lightdir.y, 0.0));
// yprime is the distance of the vertex into sun direction
yprime = -dot(relPos, lightHorizon);
// this gets an altitude correction, higher terrain gets to see the sun earlier
yprime_alt = yprime - sqrt(2.0 * EarthRadius * vertex_alt);
// two times terminator width governs how quickly light fades into shadow
// now the light-dimming factor
earthShade = 0.6 * (1.0 - smoothstep(-terminator_width+ terminator, terminator_width + terminator, yprime_alt)) + 0.4;
// parametrized version of the Flightgear ground lighting function
lightArg = (terminator-yprime_alt)/100000.0;
specular_light.b = light_func(lightArg, 1.330e-05, 0.264, 3.827, 1.08e-05, 1.0);
specular_light.g = light_func(lightArg, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
specular_light.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
specular_light = specular_light * scattering;
// correct ambient light intensity and hue before sunrise
if (earthShade < 0.5)
{
intensity = length(specular_light.rgb);
specular_light.xyz = intensity * normalize(mix(specular_light.xyz, vec3 (0.45, 0.6, 0.8), 1.0 -smoothstep(0.1, 0.7,earthShade) ));
}
// directional scattering for low sun
if (lightArg < 10.0)
//{mie_angle = (0.5 * dot(normalize(relPos), normalize(lightFull)) ) + 0.5;}
{mie_angle = (0.5 * dot(normalize(relPos), lightdir) ) + 0.5;}
else
{mie_angle = 1.0;}
// the haze gets the light at the altitude of the haze top if the vertex in view is below
// but the light at the vertex if the vertex is above
vertex_alt = max(vertex_alt,hazeLayerAltitude);
if (vertex_alt > hazeLayerAltitude)
{
if (dist > 0.8 * avisibility)
{
vertex_alt = mix(vertex_alt, hazeLayerAltitude, smoothstep(0.8*avisibility, avisibility, dist));
yprime_alt = yprime -sqrt(2.0 * EarthRadius * vertex_alt);
}
}
else
{
vertex_alt = hazeLayerAltitude;
yprime_alt = yprime -sqrt(2.0 * EarthRadius * vertex_alt);
}
}
else // the faster, full-day version without lightfields
{
//vertex_alt = max(gl_Vertex.z,100.0);
earthShade = 1.0;
mie_angle = 1.0;
if (terminator > 3000000.0)
{specular_light = vec3 (1.0, 1.0, 1.0);}
else
{
lightArg = (terminator/100000.0 - 10.0)/20.0;
specular_light.b = 0.78 + lightArg * 0.21;
specular_light.g = 0.907 + lightArg * 0.091;
specular_light.r = 0.904 + lightArg * 0.092;
}
specular_light = specular_light * scattering;
yprime_alt = -sqrt(2.0 * EarthRadius * hazeLayerAltitude);
}
}