76 lines
2.4 KiB
GLSL
76 lines
2.4 KiB
GLSL
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// -*-C++-*-
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#version 120
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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 float eye_alt;
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uniform float moonlight;
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uniform float alt_agl;
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uniform float gear_clearance;
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const float EarthRadius = 5800000.0;
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const float terminator_width = 200000.0;
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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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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()
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{
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gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
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vec4 ep = gl_ModelViewMatrixInverse * vec4(0.0,0.0,0.0,1.0);
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vec3 relPos = gl_Vertex.xyz - ep.xyz;
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// compute the strength of light
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float vertex_alt = max(gl_Vertex.z,100.0);
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float scattering = ground_scattering + (1.0 - ground_scattering) * smoothstep(hazeLayerAltitude -100.0, hazeLayerAltitude + 100.0, vertex_alt);
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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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float yprime = -dot(relPos, lightHorizon);
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float yprime_alt = yprime - sqrt(2.0 * EarthRadius * vertex_alt);
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float earthShade = 0.6 * (1.0 - smoothstep(-terminator_width+ terminator, terminator_width + terminator, yprime_alt)) + 0.4;
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float lightArg = (terminator-yprime_alt)/100000.0;
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vec4 light_diffuse;
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light_diffuse.b = light_func(lightArg, 1.330e-05, 0.264, 3.827, 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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light_diffuse = light_diffuse * scattering;
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float shade_depth = 1.0 * smoothstep (0.6,0.95,ground_scattering) * (1.0-smoothstep(0.1,0.5,overcast)) * smoothstep(0.4,1.5,earthShade);
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light_diffuse.rgb = light_diffuse.rgb * (1.0 + 1.2 * shade_depth);
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// project the shadow onto the ground
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vec4 pos = gl_Vertex;
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pos.z-=0.95 * alt_agl-0.1;
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pos.xy -= lightFull.xy * 0.95* alt_agl/lightFull.z;
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// enlargen the shadow for low light
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if (dot(pos.xy, lightHorizon.xy)<0.0)
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{
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pos.xy -= lightFull.xy * gear_clearance/lightFull.z;
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}
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gl_Position = gl_ModelViewProjectionMatrix * pos;
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gl_FrontColor = light_diffuse;
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gl_BackColor = gl_FrontColor;
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}
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