229 lines
6.9 KiB
GLSL
229 lines
6.9 KiB
GLSL
// This shader is mostly an adaptation of the shader found at
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// http://www.bonzaisoftware.com/water_tut.html and its glsl conversion
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// available at http://forum.bonzaisoftware.com/viewthread.php?tid=10
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// © Michael Horsch - 2005
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// Major update and revisions - 2011-10-07
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// © Emilian Huminiuc and Vivian Meazza
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// Optimisation - 2012-5-05
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// © Emilian Huminiuc and Vivian Meazza
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// Ported to the Atmospheric Light Scattering Framework
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// by Thorsten Renk, Aug. 2013
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#version 120
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#define fps2kts 0.5925
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varying vec4 waterTex1;
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varying vec4 waterTex2;
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varying vec3 relPos;
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varying vec3 rawPos;
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varying vec3 viewerdir;
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varying vec3 lightdir;
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varying vec3 normal;
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varying float steepness;
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varying float earthShade;
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varying float yprime_alt;
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varying float mie_angle;
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uniform float osg_SimulationTime;
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uniform float WindE, WindN, spd, hdg;
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uniform float hazeLayerAltitude;
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uniform float terminator;
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uniform float terrain_alt;
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uniform float avisibility;
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uniform float visibility;
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uniform float overcast;
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uniform float ground_scattering;
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uniform mat4 osg_ViewMatrixInverse;
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vec3 specular_light;
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// This is the value used in the skydome scattering shader - use the same here for consistency?
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const float EarthRadius = 5800000.0;
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const float terminator_width = 200000.0;
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/////////////////////////
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/////// functions /////////
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void relWind(out float rel_wind_speed_kts, float rel_wind_from_deg)
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{
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//calculate the carrier speed north and east in kts
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float speed_north_kts = cos(radians(hdg)) * spd ;
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float speed_east_kts = sin(radians(hdg)) * spd ;
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//calculate the relative wind speed north and east in kts
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float rel_wind_speed_from_east_kts = WindE*fps2kts + speed_east_kts;
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float rel_wind_speed_from_north_kts = WindN*fps2kts + speed_north_kts;
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//combine relative speeds north and east to get relative windspeed in kts
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rel_wind_speed_kts = sqrt((rel_wind_speed_from_east_kts * rel_wind_speed_from_east_kts) + (rel_wind_speed_from_north_kts * rel_wind_speed_from_north_kts));
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//calculate the relative wind direction
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rel_wind_from_deg = degrees(atan(rel_wind_speed_from_east_kts, rel_wind_speed_from_north_kts));
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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 < -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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void main(void)
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{
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float relWindspd=0;
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float relWinddir=0;
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//compute relative wind speed and direction
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relWind (relWindspd, relWinddir);
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vec3 N = normalize(gl_Normal);
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normal = N;
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viewerdir = vec3(gl_ModelViewMatrixInverse[3]) - vec3(gl_Vertex);
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lightdir = normalize(vec3(gl_ModelViewMatrixInverse * gl_LightSource[0].position));
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vec3 shadedFogColor = vec3(0.55, 0.67, 0.88);
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rawPos = (osg_ViewMatrixInverse *gl_ModelViewMatrix * gl_Vertex).xyz;
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vec4 t1 = vec4(osg_SimulationTime*0.005217, 0.0, 0.0, 0.0);
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vec4 t2 = vec4(osg_SimulationTime*-0.0012, 0.0, 0.0, 0.0);
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float windFactor = -relWindspd * 0.1;
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// float windFactor = sqrt(pow(abs(WindE),2)+pow(abs(WindN),2)) * 0.6;
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waterTex1 = gl_MultiTexCoord0 + t1 * windFactor;
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waterTex2 = gl_MultiTexCoord0 + t2 * windFactor;
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gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
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gl_Position = ftransform();
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// here start computations for the haze layer
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float yprime;
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float lightArg;
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float intensity;
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float vertex_alt;
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float scattering;
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// we need several geometrical quantities
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// first current altitude of eye position in model space
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vec4 ep = gl_ModelViewMatrixInverse * vec4(0.0,0.0,0.0,1.0);
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// and relative position to vector
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relPos = gl_Vertex.xyz - ep.xyz;
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// unfortunately, we need the distance in the vertex shader, although the more accurate version
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// is later computed in the fragment shader again
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float dist = length(relPos);
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// altitude of the vertex in question, somehow zero leads to artefacts, so ensure it is at least 100m
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vertex_alt = max(gl_Vertex.z,100.0);
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scattering = 0.5 + 0.5 * ground_scattering + 0.5* (1.0 - ground_scattering) * smoothstep(hazeLayerAltitude -100.0, hazeLayerAltitude + 100.0, vertex_alt);
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// branch dependent on daytime
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if (terminator < 1000000.0) // the full, sunrise and sunset computation
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{
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// establish coordinates relative to sun position
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vec3 lightHorizon = normalize(vec3(lightdir.x,lightdir.y, 0.0));
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// yprime is the distance of the vertex into sun direction
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yprime = -dot(relPos, lightHorizon);
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// this gets an altitude correction, higher terrain gets to see the sun earlier
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yprime_alt = yprime - sqrt(2.0 * EarthRadius * vertex_alt);
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// two times terminator width governs how quickly light fades into shadow
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// now the light-dimming factor
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earthShade = 0.6 * (1.0 - smoothstep(-terminator_width+ terminator, terminator_width + terminator, yprime_alt)) + 0.4;
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// parametrized version of the Flightgear ground lighting function
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lightArg = (terminator-yprime_alt)/100000.0;
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specular_light.b = light_func(lightArg, 1.330e-05, 0.264, 3.827, 1.08e-05, 1.0);
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specular_light.g = light_func(lightArg, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
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specular_light.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
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specular_light = max(specular_light * scattering, vec3 (0.05, 0.05, 0.05));
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intensity = length(specular_light.rgb);
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specular_light.rgb = intensity * normalize(mix(specular_light.rgb, shadedFogColor, 1.0 -smoothstep(0.1, 0.6,ground_scattering) ));
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specular_light.rgb = intensity * normalize(mix(specular_light.rgb, shadedFogColor, 1.0 -smoothstep(0.5, 0.7,earthShade)));
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// directional scattering for low sun
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if (lightArg < 10.0)
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{mie_angle = (0.5 * dot(normalize(relPos), lightdir) ) + 0.5;}
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else
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{mie_angle = 1.0;}
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// the haze gets the light at the altitude of the haze top if the vertex in view is below
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// but the light at the vertex if the vertex is above
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vertex_alt = max(vertex_alt,hazeLayerAltitude);
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if (vertex_alt > hazeLayerAltitude)
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{
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if (dist > 0.8 * avisibility)
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{
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vertex_alt = mix(vertex_alt, hazeLayerAltitude, smoothstep(0.8*avisibility, avisibility, dist));
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yprime_alt = yprime -sqrt(2.0 * EarthRadius * vertex_alt);
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}
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}
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else
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{
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vertex_alt = hazeLayerAltitude;
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yprime_alt = yprime -sqrt(2.0 * EarthRadius * vertex_alt);
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}
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}
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else // the faster, full-day version without lightfields
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{
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//vertex_alt = max(gl_Vertex.z,100.0);
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earthShade = 1.0;
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mie_angle = 1.0;
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if (terminator > 3000000.0)
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{specular_light = vec3 (1.0, 1.0, 1.0);}
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else
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{
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lightArg = (terminator/100000.0 - 10.0)/20.0;
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specular_light.b = 0.78 + lightArg * 0.21;
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specular_light.g = 0.907 + lightArg * 0.091;
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specular_light.r = 0.904 + lightArg * 0.092;
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}
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specular_light = specular_light * scattering;
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yprime_alt = -sqrt(2.0 * EarthRadius * hazeLayerAltitude);
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}
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gl_FrontColor.rgb = specular_light;
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gl_BackColor.rgb = gl_FrontColor.rgb;
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}
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