137 lines
4.9 KiB
GLSL
137 lines
4.9 KiB
GLSL
// -*-C++-*-
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#version 120
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varying float fogFactor;
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varying vec3 hazeColor;
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uniform float terminator;
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uniform float altitude;
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uniform float cloud_self_shading;
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uniform float moonlight;
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const float shade = 1.0;
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const float cloud_height = 1000.0;
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const float EarthRadius = 5800000.0;
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vec3 moonlight_perception (in vec3 light);
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// light_func is a generalized logistic function fit to the light intensity as a function
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// of scaled terminator position obtained from Flightgear core
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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 > 30.0) {return e;}
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if (x < -15.0) {return 0.03;}
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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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vec3 shadedFogColor = vec3 (0.55, 0.67, 0.88);
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vec3 moonLightColor = vec3 (0.095, 0.095, 0.15) * moonlight;
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moonLightColor = moonlight_perception (moonLightColor);
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gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
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//gl_TexCoord[0] = gl_MultiTexCoord0 + vec4(textureIndexX, textureIndexY, 0.0, 0.0);
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vec4 ep = gl_ModelViewMatrixInverse * vec4(0.0,0.0,0.0,1.0);
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vec4 l = gl_ModelViewMatrixInverse * vec4(0.0,0.0,1.0,1.0);
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vec3 u = normalize(ep.xyz - l.xyz);
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gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
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gl_Position.x = gl_Vertex.x;
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gl_Position.y += gl_Vertex.y;
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gl_Position.z += gl_Vertex.z;
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gl_Position.xyz += gl_Color.xyz;
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// Determine a lighting normal based on the vertex position from the
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// center of the cloud, so that sprite on the opposite side of the cloud to the sun are darker.
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float n = dot(normalize(-gl_LightSource[0].position.xyz),
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normalize(mat3x3(gl_ModelViewMatrix) * (- gl_Position.xyz)));;
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// Determine the position - used for fog and shading calculations
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vec3 ecPosition = vec3(gl_ModelViewMatrix * gl_Position);
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float fogCoord = abs(ecPosition.z);
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float fract = smoothstep(0.0, cloud_height, gl_Position.z + cloud_height);
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vec3 relVector = gl_Position.xyz - ep.xyz;
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gl_Position = gl_ModelViewProjectionMatrix * gl_Position;
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// Light at the final position
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// first obtain normal to sun position
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vec3 lightFull = (gl_ModelViewMatrixInverse * gl_LightSource[0].position).xyz;
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vec3 lightHorizon = normalize(vec3(lightFull.x,lightFull.y, 0.0));
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// yprime is the distance of the vertex into sun direction, corrected for altitude
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//float vertex_alt = max(altitude * 0.30480 + relVector.z,100.0);
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float vertex_alt = altitude + relVector.z;
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float yprime = -dot(relVector, lightHorizon);
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float yprime_alt = yprime -sqrt(2.0 * EarthRadius * vertex_alt);
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// compute the light at the position
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vec4 light_diffuse;
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float lightArg = (terminator-yprime_alt)/100000.0;
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light_diffuse.b = light_func(lightArg, 1.330e-05, 0.264, 2.227, 1.08e-05, 1.0);
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light_diffuse.g = light_func(lightArg, 3.931e-06, 0.264, 3.827, 7.93e-06, 1.0);
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light_diffuse.r = light_func(lightArg, 8.305e-06, 0.161, 3.827, 3.04e-05, 1.0);
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light_diffuse.a = 1.0;
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float intensity = length(light_diffuse.rgb);
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light_diffuse.rgb = intensity * normalize(mix(light_diffuse.rgb, shadedFogColor, (1.0 - smoothstep(0.5,0.9, cloud_self_shading ))));
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// Determine the shading of the sprite based on its vertical position and position relative to the sun.
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n = min(smoothstep(-0.5, 0.0, n), fract);
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// Determine the shading based on a mixture from the backlight to the front
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vec4 backlight = light_diffuse * shade;
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gl_FrontColor = mix(backlight, light_diffuse, n);
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gl_FrontColor += gl_FrontLightModelProduct.sceneColor;
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// As we get within 100m of the sprite, it is faded out. Equally at large distances it also fades out.
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gl_FrontColor.a = min(smoothstep(100.0, 250.0, fogCoord), 1.0 - smoothstep(70000.0, 75000.0, fogCoord));
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// Fog doesn't affect rain as much as other objects.
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//fogFactor = exp( -gl_Fog.density * fogCoord * 0.4);
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//fogFactor = clamp(fogFactor, 0.0, 1.0);
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float fadeScale = 0.05 + 0.2 * log(fogCoord/1000.0);
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if (fadeScale < 0.05) fadeScale = 0.05;
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fogFactor = exp( -gl_Fog.density * fogCoord * fadeScale);
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hazeColor = light_diffuse.rgb;
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hazeColor.r = hazeColor.r * 0.83;
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hazeColor.g = hazeColor.g * 0.9;
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// in sunset or sunrise conditions, do extra shading of clouds
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// two times terminator width governs how quickly light fades into shadow
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float terminator_width = 200000.0;
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// now dim the light
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float earthShade = 0.9 * smoothstep(terminator_width+ terminator, -terminator_width + terminator, yprime_alt) + 0.1;
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if (earthShade < 0.8)
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{
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intensity = length(light_diffuse.rgb);
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gl_FrontColor.rgb = intensity * normalize(mix(gl_FrontColor.rgb, shadedFogColor, 1.0 -smoothstep(0.1, 0.8,earthShade ) ));
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}
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hazeColor = hazeColor * earthShade;
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gl_FrontColor.rgb = gl_FrontColor.rgb * earthShade;
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gl_FrontColor.rgb = gl_FrontColor.rgb + moonLightColor * (1.0 - smoothstep(0.4, 0.5, earthShade));
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hazeColor.rgb = hazeColor.rgb + moonLightColor * (1.0 - smoothstep(0.4, 0.5, earthShade));
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gl_BackColor = gl_FrontColor;
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}
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