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'The Flag' for Atmospheric Light Scattering

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Thorsten Renk 2013-03-01 09:11:10 +02:00
parent 1c324de144
commit 9ffb8a3d52
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219
Effects/flutter.eff
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@ -48,6 +48,225 @@
<!-- END fog include -->
</parameters>
<technique n="3">
<predicate>
<and>
<property>/sim/rendering/shaders/skydome</property>
<or>
<less-equal>
<value type="float">2.0</value>
<glversion/>
</less-equal>
<and>
<extension-supported>GL_ARB_shader_objects</extension-supported>
<extension-supported>GL_ARB_shading_language_100</extension-supported>
<extension-supported>GL_ARB_vertex_shader</extension-supported>
<extension-supported>GL_ARB_fragment_shader</extension-supported>
</and>
</or>
</and>
</predicate>
<pass>
<lighting>true</lighting>
<material>
<active>
<use>material/active</use>
</active>
<ambient>
<use>material/ambient</use>
</ambient>
<diffuse>
<use>material/diffuse</use>
</diffuse>
<specular>
<use>material/specular</use>
</specular>
<emissive>
<use>material/emissive</use>
</emissive>
<shininess>
<use>material/shininess</use>
</shininess>
<color-mode>
<use>material/color-mode</use>
</color-mode>
</material>
<blend>
<active>
<use>blend/active</use>
</active>
<source>
<use>blend/source</use>
</source>
<destination>
<use>blend/destination</use>
</destination>
</blend>
<shade-model>
<use>shade-model</use>
</shade-model>
<cull-face>
<use>cull-face</use>
</cull-face>
<rendering-hint>
<use>rendering-hint</use>
</rendering-hint>
<texture-unit>
<!-- The texture unit is always active because the shaders expect
that. -->
<unit>0</unit>
<!-- If there is a texture, the type in the derived effect
will be "2d". -->
<type>
<use>texture[0]/type</use>
</type>
<image>
<use>texture[0]/image</use>
</image>
<filter>
<use>texture[0]/filter</use>
</filter>
<wrap-s>
<use>texture[0]/wrap-s</use>
</wrap-s>
<wrap-t>
<use>texture[0]/wrap-t</use>
</wrap-t>
<!--
<internal-format>
<use>texture[0]/internal-format</use>
</internal-format>
-->
</texture-unit>
<texture-unit>
<unit>1</unit>
<type>noise</type>
</texture-unit>
<vertex-program-two-side>
<use>vertex-program-two-side</use>
</vertex-program-two-side>
<program>
<vertex-shader>Shaders/flutter-lightfield.vert</vertex-shader>
<fragment-shader>Shaders/terrain-haze.frag</fragment-shader>
</program>
<!--<uniform>
<name>texture</name>
<type>sampler-2d</type>
<value type="int">0</value>
</uniform>-->
<uniform>
<name>colorMode</name>
<type>int</type>
<value>
<use>material/color-mode-uniform</use>
</value>
</uniform>
<!-- uniform> unused?
<name>WindSpeed</name>
<type>float</type>
<value>
<use>wind-speed</use>
</value>
</uniform-->
<uniform>
<name>Offset</name>
<type>float</type>
<value>
<use>offset</use>
</value>
</uniform>
<uniform>
<name>AmpFactor</name>
<type>float</type>
<value>
<use>amplitude-factor</use>
</value>
</uniform>
<uniform>
<name>Noise</name>
<type>sampler-3d</type>
<value type="int">1</value>
</uniform>
<uniform>
<name>WindE</name>
<type>float</type>
<value>
<use>windE</use>
</value>
</uniform>
<uniform>
<name>WindN</name>
<type>float</type>
<value>
<use>windN</use>
</value>
</uniform>
<uniform>
<name>spd</name>
<type>float</type>
<value>
<use>speed-kt</use>
</value>
</uniform>
<uniform>
<name>hdg</name>
<type>float</type>
<value>
<use>heading-deg</use>
</value>
</uniform>
<!-- BEGIN fog include -->
<uniform>
<name>visibility</name>
<type>float</type>
<value>
<use>visibility</use>
</value>
</uniform>
<uniform>
<name>avisibility</name>
<type>float</type>
<value>
<use>avisibility</use>
</value>
</uniform>
<uniform>
<name>hazeLayerAltitude</name>
<type>float</type>
<value>
<use>lthickness</use>
</value>
</uniform>
<uniform>
<name>scattering</name>
<type>float</type>
<value>
<use>scattering</use>
</value>
</uniform>
<uniform>
<name>terminator</name>
<type>float</type>
<value>
<use>terminator</use>
</value>
</uniform>
<uniform>
<name>fogType</name>
<type>int</type>
<value>
<use>fogtype</use>
</value>
</uniform>
<!-- END fog include -->
</pass>
</technique>
<technique n="9">
<predicate>
<and>

312
Shaders/flutter-lightfield.vert Normal file
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@ -0,0 +1,312 @@
// -*-C++-*-
// © Vivian Meazza - 2011
// adapted to Atmospheric Light Scattering by Thorsten Renk 2013
// Shader that uses OpenGL state values to do per-pixel lighting
//
// The only light used is gl_LightSource[0], which is assumed to be
// directional.
//
// Diffuse colors come from the gl_Color, ambient from the material. This is
// equivalent to osg::Material::DIFFUSE.
#version 120
#define fps2kts 0.5925
#define MODE_OFF 0
#define MODE_DIFFUSE 1
#define MODE_AMBIENT_AND_DIFFUSE 2
// The ambient term of the lighting equation that doesn't depend on
// the surface normal is passed in gl_{Front,Back}Color. The alpha
// component is set to 1 for front, 0 for back in order to work around
// bugs with gl_FrontFacing in the fragment shader.
varying vec4 diffuse_term;
varying vec3 normal;
varying vec3 relPos;
varying float yprime_alt;
varying float mie_angle;
uniform int colorMode;
uniform float osg_SimulationTime;
uniform float Offset, AmpFactor, WindE, WindN, spd, hdg;
uniform sampler3D Noise;
uniform float hazeLayerAltitude;
uniform float terminator;
uniform float terrain_alt;
uniform float avisibility;
uniform float visibility;
uniform float overcast;
uniform float ground_scattering;
uniform float moonlight;
// 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 earthShade;
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));
}
float normalize_range(float _val)
{
if (_val > 180.0)
return _val - 360.0;
else
return _val;
}
void relWind(out float rel_wind_speed_kts, out float rel_wind_from_rad)
{
//calculate speed north and east in kts
float speed_north_kts = cos(radians(hdg)) * spd ;
float speed_east_kts = sin(radians(hdg)) * spd ;
//calculate the relative wind speed north and east in kts
float rel_wind_speed_from_east_kts = WindE*fps2kts + speed_east_kts;
float rel_wind_speed_from_north_kts = WindN*fps2kts + speed_north_kts;
//combine relative speeds north and east to get relative windspeed in kts
rel_wind_speed_kts = sqrt(pow(abs(rel_wind_speed_from_east_kts), 2.0)
+ pow(abs(rel_wind_speed_from_north_kts), 2.0));
//calculate the relative wind direction
float rel_wind_from_deg = degrees(atan(rel_wind_speed_from_east_kts, rel_wind_speed_from_north_kts));
//rel_wind_from_rad = atan(rel_wind_speed_from_east_kts, rel_wind_speed_from_north_kts);
float rel_wind = rel_wind_from_deg - hdg;
rel_wind = normalize_range(rel_wind);
rel_wind_from_rad = radians(rel_wind);
}
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()
{
vec4 light_diffuse;
vec4 light_ambient;
vec3 shadedFogColor = vec3(0.65, 0.67, 0.78);
vec3 moonLightColor = vec3 (0.095, 0.095, 0.15) * moonlight;
float yprime;
float lightArg;
float intensity;
float vertex_alt;
float scattering;
mat4 RotationMatrix;
float relWindspd=0.0;
float relWinddir=0.0;
// compute relative wind speed and direction
relWind (relWindspd, relWinddir);
// map noise vector
vec4 noisevec = texture3D(Noise, gl_Vertex.xyz);
//waving effect
float tsec = osg_SimulationTime;
vec4 pos = gl_Vertex;
vec4 oldpos = gl_Vertex;
float freq = (10.0 * relWindspd) + 10.0;
pos.y = sin((pos.x * 5.0 + tsec * freq )/5.0) * 0.5 ;
pos.y += sin((pos.z * 5.0 + tsec * freq/2.0)/5.0) * 0.125 ;
pos.y *= pow(pos.x - Offset, 2.0) * AmpFactor;
//rotate the flag to align with relative wind
rotationmatrix(-relWinddir, RotationMatrix);
pos *= RotationMatrix;
gl_Position = gl_ModelViewProjectionMatrix * pos;
//do the colour and fog
vec4 ecPosition = gl_ModelViewMatrix * gl_Vertex;
gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
normal = gl_NormalMatrix * gl_Normal;
vec4 ambient_color, diffuse_color;
if (colorMode == MODE_DIFFUSE) {
diffuse_color = gl_Color;
ambient_color = gl_FrontMaterial.ambient;
} else if (colorMode == MODE_AMBIENT_AND_DIFFUSE) {
diffuse_color = gl_Color;
ambient_color = gl_Color;
} else {
diffuse_color = gl_FrontMaterial.diffuse;
ambient_color = gl_FrontMaterial.ambient;
}
// 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 = ground_scattering + (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));
// 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;
// directional scattering for low sun
if (lightArg < 10.0)
{mie_angle = (0.5 * dot(normalize(relPos), normalize(lightFull)) ) + 0.5;}
else
{mie_angle = 1.0;}
light_diffuse.b = light_func(lightArg, 1.330e-05, 0.264, 3.827, 1.08e-05, 1.0);
light_diffuse.g = light_func(lightArg, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
light_diffuse.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
light_diffuse.a = 1.0;
light_diffuse = light_diffuse * scattering;
light_ambient.r = light_func(lightArg, 0.236, 0.253, 1.073, 0.572, 0.33);
light_ambient.g = light_ambient.r * 0.4/0.33;
light_ambient.b = light_ambient.r * 0.5/0.33;
light_ambient.a = 1.0;
// correct ambient light intensity and hue before sunrise
if (earthShade < 0.5)
{
//light_ambient = light_ambient * (0.7 + 0.3 * smoothstep(0.2, 0.5, earthShade));
intensity = length(light_ambient.xyz);
light_ambient.rgb = intensity * normalize(mix(light_ambient.rgb, shadedFogColor, 1.0 -smoothstep(0.1, 0.8,earthShade) ));
light_ambient.rgb = light_ambient.rgb + moonLightColor * (1.0 - smoothstep(0.4, 0.5, earthShade));
intensity = length(light_diffuse.xyz);
light_diffuse.rgb = intensity * normalize(mix(light_diffuse.rgb, shadedFogColor, 1.0 -smoothstep(0.1, 0.7,earthShade) ));
}
// 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)
{light_diffuse = vec4 (1.0, 1.0, 1.0, 0.0);
light_ambient = vec4 (0.33, 0.4, 0.5, 0.0); }
else
{
lightArg = (terminator/100000.0 - 10.0)/20.0;
light_diffuse.b = 0.78 + lightArg * 0.21;
light_diffuse.g = 0.907 + lightArg * 0.091;
light_diffuse.r = 0.904 + lightArg * 0.092;
light_diffuse.a = 1.0;
light_ambient.r = 0.316 + lightArg * 0.016;
light_ambient.g = light_ambient.r * 0.4/0.33;
light_ambient.b = light_ambient.r * 0.5/0.33;
light_ambient.a = 1.0;
}
light_diffuse = light_diffuse * scattering;
yprime_alt = -sqrt(2.0 * EarthRadius * hazeLayerAltitude);
}
diffuse_term = diffuse_color * light_diffuse;
vec4 ambient_term = ambient_color * light_ambient;
// Super hack: if diffuse material alpha is less than 1, assume a
// transparency animation is at work
if (gl_FrontMaterial.diffuse.a < 1.0)
diffuse_term.a = gl_FrontMaterial.diffuse.a;
else
diffuse_term.a = gl_Color.a;
// Another hack for supporting two-sided lighting without using
// gl_FrontFacing in the fragment shader.
gl_FrontColor.rgb = ambient_term.rgb; gl_FrontColor.a = 0.0;
gl_BackColor.rgb = ambient_term.rgb; gl_FrontColor.a = 1.0;
// fogCoord = abs(ecPosition.z / ecPosition.w);
//fog_Func(fogType);
}