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Add support for atmospheric scattering to the random vegetation shader.

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Stuart Buchanan 2012-06-30 00:38:14 +01:00
parent b466346a53
commit 145a759fb8
3 changed files with 689 additions and 18 deletions
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174
Effects/tree.eff
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@ -17,26 +17,164 @@
<texture n ="0"> <texture n ="0">
</texture> </texture>
<!-- fog include --> <!-- fog include -->
<visibility> <visibility><use>/environment/ground-visibility-m</use></visibility>
<use>/environment/ground-visibility-m</use> <avisibility><use>/environment/visibility-m</use></avisibility>
</visibility> <lthickness><use>/environment/ground-haze-thickness-m</use></lthickness>
<avisibility> <scattering><use>/rendering/scene/scattering</use></scattering>
<use>/environment/visibility-m</use> <ground_scattering><use>/environment/surface/scattering</use></ground_scattering>
</avisibility> <terminator><use>/environment/terminator-relative-position-m</use></terminator>
<lthickness> <fogtype><use>/sim/rendering/shaders/skydome</use></fogtype>
<use>/environment/ground-haze-thickness-m</use> <terrain_alt><use>/environment/mean-terrain-elevation-m</use></terrain_alt>
</lthickness> <overcast><use>/rendering/scene/overcast</use></overcast>
<scattering> <eye_alt><use>/sim/rendering/eye-altitude-m</use></eye_alt>
<use>/rendering/scene/scattering</use> <mysnow_level><use>/environment/mysnow-level-m</use></mysnow_level>
</scattering> <dust_cover_factor><use>/environment/surface/dust-cover-factor</use></dust_cover_factor>
<terminator> <fogtype><use>/sim/rendering/shaders/skydome</use></fogtype>
<use>/environment/terminator-relative-position-m</use> <fogstructure><use>/environment/fog-structure</use></fogstructure>
</terminator> <render-bin-number><use>/sim/rendering/tree-bin</use></render-bin-number>
<fogtype> <render-bin-name><use>/sim/rendering/tree-bin-name</use></render-bin-name>
<use>/sim/rendering/shaders/skydome</use>
</fogtype>
<!-- END fog include --> <!-- END fog include -->
</parameters> </parameters>
<technique n="5">
<predicate>
<and>
<property>/sim/rendering/shaders/skydome</property>
<property>/sim/rendering/random-vegetation</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>
<ambient type="vec4d">1.0 1.0 1.0 1.0</ambient>
<diffuse type="vec4d">1.0 1.0 1.0 1.0</diffuse>
<color-mode>off</color-mode>
</material>
<render-bin>
<bin-number>-1</bin-number>
<bin-name>RenderBin</bin-name>
</render-bin>
<blend>
<source>src-alpha</source>
<destination>one-minus-src-alpha</destination>
</blend>
<texture-unit>
<unit>0</unit>
<type>2d</type>
<image>
<use>texture[0]/image</use>
</image>
<wrap-s>clamp</wrap-s>
<wrap-t>clamp</wrap-t>
</texture-unit>
<program>
<!-- <vertex-shader n="0">Shaders/include_fog.vert</vertex-shader> -->
<vertex-shader n="1">Shaders/tree.vert</vertex-shader>
<fragment-shader n="0">Shaders/include_fog.frag</fragment-shader>
<fragment-shader n="1">Shaders/tree.frag</fragment-shader>
</program>
<uniform>
<name>texture</name>
<type>sampler-2d</type>
<value type="int">0</value>
</uniform>
<color-mask type="vec4d">0 0 0 0</color-mask>
</pass>
<pass>
<lighting>true</lighting>
<material>
<ambient type="vec4d">1.0 1.0 1.0 1.0</ambient>
<diffuse type="vec4d">1.0 1.0 1.0 1.0</diffuse>
<color-mode>off</color-mode>
</material>
<texture-unit>
<unit>0</unit>
<type>2d</type>
<image>
<use>texture[0]/image</use>
</image>
<wrap-s>clamp</wrap-s>
<wrap-t>clamp</wrap-t>
</texture-unit>
<program>
<vertex-shader>Shaders/tree-haze.vert</vertex-shader>
<fragment-shader>Shaders/tree-haze.frag</fragment-shader>
</program>
<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>ground_scattering</name>
<type>float</type>
<value><use>ground_scattering</use></value>
</uniform>
<uniform>
<name>terminator</name>
<type>float</type>
<value><use>terminator</use></value>
</uniform>
<uniform>
<name>terrain_alt</name>
<type>float</type>
<value><use>terrain_alt</use></value>
</uniform>
<uniform>
<name>overcast</name>
<type>float</type>
<value><use>overcast</use></value>
</uniform>
<uniform>
<name>eye_alt</name>
<type>float</type>
<value><use>eye_alt</use></value>
</uniform>
<uniform>
<name>texture</name>
<type>sampler-2d</type>
<value type="int">0</value>
</uniform>
<uniform>
<name>colorMode</name>
<type>int</type>
<value>2</value> <!-- AMBIENT_AND_DIFFUSE -->
</uniform>
<depth>
<function>lequal</function>
<write-mask type="bool">false</write-mask>
</depth>
</pass>
</technique>
<technique n="9"> <technique n="9">
<predicate> <predicate>
<and> <and>

288
Shaders/tree-haze.frag Normal file
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// -*-C++-*-
// written by Thorsten Renk, Oct 2011, based on default.frag
// Ambient term comes in gl_Color.rgb.
varying vec4 diffuse_term;
varying vec3 normal;
varying vec3 relPos;
//varying vec3 hazeColor;
//varying float fogCoord;
uniform sampler2D texture;
//varying float ct;
//varying float delta_z;
//varying float alt;
varying float earthShade;
//varying float yprime;
//varying float vertex_alt;
varying float yprime_alt;
varying float mie_angle;
uniform float visibility;
uniform float avisibility;
uniform float scattering;
//uniform float ground_scattering;
uniform float terminator;
uniform float terrain_alt;
uniform float hazeLayerAltitude;
uniform float overcast;
//uniform float altitude;
uniform float eye_alt;
const float EarthRadius = 5800000.0;
const float terminator_width = 200000.0;
float alt;
float luminance(vec3 color)
{
return dot(vec3(0.212671, 0.715160, 0.072169), color);
}
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 > 30.0) {return e;}
if (x < -15.0) {return 0.0;}
return e / pow((1.0 + a * exp(-b * (x-c)) ),(1.0/d));
}
// this determines how light is attenuated in the distance
// physically this should be exp(-arg) but for technical reasons we use a sharper cutoff
// for distance > visibility
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; // 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()
{
// this is taken from default.frag
vec3 n;
float NdotL, NdotHV, fogFactor;
vec4 color = gl_Color;
vec3 lightDir = gl_LightSource[0].position.xyz;
vec3 halfVector = gl_LightSource[0].halfVector.xyz;
vec4 texel;
vec4 fragColor;
vec4 specular = vec4(0.0);
float intensity;
vec4 light_specular = gl_LightSource[0].specular;
// If gl_Color.a == 0, this is a back-facing polygon and the
// normal should be reversed.
n = (2.0 * gl_Color.a - 1.0) * normal;
n = normalize(n);
NdotL = dot(n, lightDir);
if (NdotL > 0.0) {
color += diffuse_term * NdotL;
NdotHV = max(dot(n, halfVector), 0.0);
if (gl_FrontMaterial.shininess > 0.0)
specular.rgb = (gl_FrontMaterial.specular.rgb
* light_specular.rgb
* pow(NdotHV, gl_FrontMaterial.shininess));
}
color.a = diffuse_term.a;
// This shouldn't be necessary, but our lighting becomes very
// saturated. Clamping the color before modulating by the texture
// is closer to what the OpenGL fixed function pipeline does.
color = clamp(color, 0.0, 1.0);
texel = texture2D(texture, gl_TexCoord[0].st);
fragColor = color * texel + specular;
// here comes the terrain haze model
float delta_z = hazeLayerAltitude - eye_alt;
float dist = length(relPos);
if (dist > 40.0)
{
alt = 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;
float eqColorFactor;
//float scattering = ground_scattering + (1.0 - ground_scattering) * smoothstep(hazeLayerAltitude -100.0, hazeLayerAltitude + 100.0, relPos.z + eye_alt);
if (visibility < avisibility)
{
transmission_arg = transmission_arg + (distance_in_layer/visibility);
// this combines the Weber-Fechner intensity
eqColorFactor = 1.0 - 0.1 * delta_zv/visibility - (1.0 -scattering);
}
else
{
transmission_arg = transmission_arg + (distance_in_layer/avisibility);
// this combines the Weber-Fechner intensity
eqColorFactor = 1.0 - 0.1 * delta_zv/avisibility - (1.0 -scattering);
}
transmission = fog_func(transmission_arg);
// there's always residual intensity, we should never be driven to zero
if (eqColorFactor < 0.2) eqColorFactor = 0.2;
float lightArg = (terminator-yprime_alt)/100000.0;
vec3 hazeColor;
hazeColor.b = light_func(lightArg, 1.330e-05, 0.264, 2.527, 1.08e-05, 1.0);
hazeColor.g = light_func(lightArg, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
hazeColor.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
// now dim the light for haze
float eShade = earthShade;
eShade = 0.9 * smoothstep(terminator_width+ terminator, -terminator_width + terminator, yprime_alt) + 0.1;
// Mie-like factor
if (lightArg < 10.0)
{intensity = length(hazeColor);
float mie_magnitude = 0.5 * smoothstep(350000.0, 150000.0, terminator-sqrt(2.0 * EarthRadius * terrain_alt));
hazeColor = intensity * ((1.0 - mie_magnitude) + mie_magnitude * mie_angle) * normalize(mix(hazeColor, vec3 (0.5, 0.58, 0.65), mie_magnitude * (0.5 - 0.5 * mie_angle)) );
}
// high altitude desaturation of the haze color
intensity = length(hazeColor);
hazeColor = intensity * normalize (mix(hazeColor, intensity * vec3 (1.0,1.0,1.0), 0.7* smoothstep(5000.0, 50000.0, alt)));
// blue hue of haze
hazeColor.x = hazeColor.x * 0.83;
hazeColor.y = hazeColor.y * 0.9;
// additional blue in indirect light
float fade_out = max(0.65 - 0.3 *overcast, 0.45);
intensity = length(hazeColor);
hazeColor = intensity * normalize(mix(hazeColor, 1.5* vec3 (0.45, 0.6, 0.8), 1.0 -smoothstep(0.25, fade_out,eShade) ));
// change haze color to blue hue for strong fogging
//intensity = length(hazeColor);
hazeColor = intensity * normalize(mix(hazeColor, 2.0 * vec3 (0.55, 0.6, 0.8), (1.0-smoothstep(0.3,0.8,eqColorFactor))));
// reduce haze intensity when looking at shaded surfaces, only in terminator region
float shadow = mix( min(1.0 + dot(normal,lightDir),1.0), 1.0, 1.0-smoothstep(0.1, 0.4, transmission));
hazeColor = mix(shadow * hazeColor, hazeColor, 0.3 + 0.7* smoothstep(250000.0, 400000.0, terminator));
// determine the right mix of transmission and haze
//fragColor.xyz = transmission * fragColor.xyz + (1.0-transmission) * eqColorFactor * hazeColor * earthShade;
fragColor.xyz = mix(eqColorFactor * hazeColor * eShade, fragColor.xyz,transmission);
gl_FragColor = fragColor;
}
else // if dist < 40.0 no fogging at all
{
gl_FragColor = fragColor;
}
}

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Shaders/tree-haze.vert Normal file
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// -*-C++-*-
// 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.
// Haze part added by Thorsten Renk, Oct. 2011
#define MODE_OFF 0
#define MODE_DIFFUSE 1
#define MODE_AMBIENT_AND_DIFFUSE 2
// The constant 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 earthShade;
//varying float yprime;
//varying float vertex_alt;
varying float yprime_alt;
varying float mie_angle;
uniform int colorMode;
uniform float hazeLayerAltitude;
uniform float terminator;
uniform float terrain_alt;
uniform float avisibility;
uniform float visibility;
uniform float overcast;
//uniform float scattering;
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));
}
void main()
{
vec4 light_diffuse;
vec4 light_ambient;
//float yprime_alt;
float yprime;
float lightArg;
float intensity;
float vertex_alt;
float scattering;
// this code is copied from tree.vert
float numVarieties = gl_Normal.z;
float texFract = floor(fract(gl_MultiTexCoord0.x) * numVarieties) / numVarieties;
texFract += floor(gl_MultiTexCoord0.x) / numVarieties;
float sr = sin(gl_FogCoord);
float cr = cos(gl_FogCoord);
gl_TexCoord[0] = vec4(texFract, gl_MultiTexCoord0.y, 0.0, 0.0);
// scaling
vec3 position = gl_Vertex.xyz * gl_Normal.xxy;
// Rotation of the generic quad to specific one for the tree.
position.xy = vec2(dot(position.xy, vec2(cr, sr)), dot(position.xy, vec2(-sr, cr)));
position = position + gl_Color.xyz;
gl_Position = gl_ModelViewProjectionMatrix * vec4(position,1.0);
vec3 ecPosition = vec3(gl_ModelViewMatrix * vec4(position, 1.0));
normal = normalize(-ecPosition);
float n = dot(normalize(gl_LightSource[0].position.xyz), normalize(-ecPosition));
vec4 diffuse_color = gl_FrontMaterial.diffuse * max(0.1, n);
//diffuse_color.a = 1.0;
vec4 ambient_color = gl_FrontLightModelProduct.sceneColor + gl_LightSource[0].ambient * gl_FrontMaterial.ambient;
// here start computations for the haze layer
// 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 = position - 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(position.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 = 0.0;
light_diffuse = light_diffuse * scattering;
light_ambient.b = light_func(lightArg, 0.000506, 0.131, -3.315, 0.000457, 0.5);
light_ambient.g = light_func(lightArg, 2.264e-05, 0.134, 0.967, 3.66e-05, 0.4);
light_ambient.r = light_func(lightArg, 0.236, 0.253, 1.073, 0.572, 0.33);
light_ambient.a = 0.0;
// correct ambient light intensity and hue before sunrise
if (earthShade < 0.5)
{
light_ambient = light_ambient * (0.4 + 0.6 * smoothstep(0.2, 0.5, earthShade));
intensity = length(light_ambient.xyz);
light_ambient.xyz = intensity * normalize(mix(light_ambient.xyz, vec3 (0.45, 0.6, 0.8), 1.0 -smoothstep(0.1, 0.5,earthShade) ));
intensity = length(light_diffuse.xyz);
light_diffuse.xyz = intensity * normalize(mix(light_diffuse.xyz, vec3 (0.45, 0.6, 0.8), 1.0 -smoothstep(0.1, 0.5,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 = 0.0;
light_ambient.b = 0.41 + lightArg * 0.08;
light_ambient.g = 0.333 + lightArg * 0.06;
light_ambient.r = 0.316 + lightArg * 0.016;
light_ambient.a = 0.0;
}
light_diffuse = light_diffuse * scattering;
yprime_alt = -sqrt(2.0 * EarthRadius * hazeLayerAltitude);
}
// default lighting based on texture and material using the light we have just computed
diffuse_term = diffuse_color* light_diffuse;
vec4 constant_term = gl_FrontMaterial.emission + ambient_color *
(gl_LightModel.ambient + 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 = constant_term.rgb; gl_FrontColor.a = 1.0;
gl_BackColor.rgb = constant_term.rgb; gl_BackColor.a = 0.0;
}