56 lines
1.4 KiB
GLSL
56 lines
1.4 KiB
GLSL
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uniform sampler2DRect osgOcean_GodRayTexture;
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uniform vec3 osgOcean_SunDir;
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uniform vec3 osgOcean_HGg; // Eccentricity constants controls power of forward scattering
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uniform float osgOcean_Intensity; // Intensity tweak for god rays
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uniform vec3 osgOcean_Eye;
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varying vec3 vRay;
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const float bias = 0.15; // used to hide aliasing
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// Mie phase function
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float computeMie(vec3 viewDir, vec3 sunDir)
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{
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float num = osgOcean_HGg.x;
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float den = (osgOcean_HGg.y - osgOcean_HGg.z*dot(sunDir, viewDir));
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den = inversesqrt(den);
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float phase = num * (den*den*den);
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return phase;
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}
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// ----------------------------------------------
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// Main Program
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// ----------------------------------------------
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void main( void )
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{
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vec4 shafts;
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// average the pixels out a little to hide aliasing
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// TODO: Maybe try a weak blur filter
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shafts += texture2DRect(osgOcean_GodRayTexture, gl_TexCoord[1].xy);
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shafts += texture2DRect(osgOcean_GodRayTexture, gl_TexCoord[1].zw);
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shafts += texture2DRect(osgOcean_GodRayTexture, gl_TexCoord[2].xy);
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shafts += texture2DRect(osgOcean_GodRayTexture, gl_TexCoord[2].zw);
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shafts /= 4.0;
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vec3 rayNormalised = normalize(vRay-osgOcean_Eye);
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float phase = computeMie(rayNormalised, -osgOcean_SunDir);
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// Calculate final color, adding a little bias (0.15 here)
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// to hide aliasing
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vec3 colour = (bias+osgOcean_Intensity*shafts.rgb)*phase;
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vec3 ray = ( rayNormalised + vec3(1.0) ) / 2.0;
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gl_FragColor = vec4(colour, 1.0);
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}
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