important skin bug

[Alessandro Padovani]

daz studio 4.15.0.2, blender 2.93.4, diffeomorphic a6a1357

This is related to #656 but reported here for better handling. It appears that the scatter color in the volumetric skin is no more inverted. The scatter color needs to be inverted compared to iray as reported in #24. I suspect this bug was introduced in #573.

Below an example with Victoria 8.1 where I fixed the torso material, first iray then cycles.

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[Thomas Larsson]

Hm. The scatter color was only inverted if the green channel was zero. I know that there was something with the green channel, but perhaps it was only relevant in some other context. Anyway, the scatter color is always inverted now.

[Alessandro Padovani]

Commit 47b6e4b works fine. Thank you Thomas for the fast fix.

What you’re talking about for the green channel is #27 that’s a fix for a iray bug in chromatic mode. But for the normal case the scatter color is inverted to start with. Anyway the fix doesn’t always work and it’s also ugly, so we may omit it in my opinion.

Below it's the up to date version of the fix, extracted form #27 and with the better factors in #117. Again we may omit it in my opinion. That is, we may ignore the green channel case.

# if there's transmission then use volume absorption
if transmitted color <> black/white
    use volume absorption
    absorption color = transmitted color
    if green(transmitted color) == 0
        absorption color = invert(transmitted color)
    density = 100 / transmitted distance

# if there's sss then use volume scatter
if chromatic sss color <> black/white
    use volume scatter
    scatter color = invert(sss color)
    if green(sss color) == 0
        scatter color = sss color
    density = 50 / scattering distance
    anisotropy = sss direction

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