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66 行
1.6 KiB
66 行
1.6 KiB
#ifndef UNITY_VOLUME_RENDERING_INCLUDED
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#define UNITY_VOLUME_RENDERING_INCLUDED
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real OpticalDepthHomogeneous(real extinction, real intervalLength)
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{
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return extinction * intervalLength;
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}
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real Transmittance(real opticalDepth)
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{
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return exp(-opticalDepth);
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}
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real TransmittanceIntegralOverHomogeneousInterval(real extinction, real start, real end)
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{
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return (exp(-extinction * start) - exp(-extinction * end)) / extinction;
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}
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real3 OpticalDepthHomogeneous(real3 extinction, real intervalLength)
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{
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return extinction * intervalLength;
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}
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real3 Transmittance(real3 opticalDepth)
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{
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return exp(-opticalDepth);
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}
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real3 TransmittanceIntegralOverHomogeneousInterval(real3 extinction, real start, real end)
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{
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return (exp(-extinction * start) - exp(-extinction * end)) / extinction;
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}
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real IsotropicPhaseFunction()
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{
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return INV_FOUR_PI;
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}
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real HenyeyGreensteinPhasePartConstant(real asymmetry)
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{
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real g = asymmetry;
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return INV_FOUR_PI * (1 - g * g);
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}
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real HenyeyGreensteinPhasePartVarying(real asymmetry, real LdotD)
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{
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real g = asymmetry;
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return pow(abs(1 + g * g - 2 * g * LdotD), -1.5);
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}
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real HenyeyGreensteinPhaseFunction(real asymmetry, real LdotD)
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{
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return HenyeyGreensteinPhasePartConstant(asymmetry) *
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HenyeyGreensteinPhasePartVarying(asymmetry, LdotD);
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}
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// Absorption coefficient from Disney: http://blog.selfshadow.com/publications/s2015-shading-course/burley/s2015_pbs_disney_bsdf_notes.pdf
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real3 TransmittanceColorAtDistanceToAbsorption(real3 transmittanceColor, real atDistance)
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{
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return -log(transmittanceColor + FLT_EPS) / max(atDistance, FLT_EPS);
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}
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#endif // UNITY_VOLUME_RENDERING_INCLUDED
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