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Iray - Cutout Opacity - White is not the same as None?

andya_b341b7c5f5andya_b341b7c5f5 Posts: 694
in Technical Help (nuts n bolts)

When I add a cutout opacity map to a G8F figure and use 'full' white (255,255,255) in the image map, I expect this to be rendered as completely opaque, white treated effectively a value of 1, and black a value of zero.  I also expect this to be equivalent of having the cutout opacity map set to None (no image) and the slider set to 1, meaning fullly opaque.  A black image certainly is the equivalent of None and the slider set to zero.

It does not seem to work like this.  The completely white parts of the image - or indeed an image that is entirely white - are both rendered as having some level of transparency, i.e. not 100% opaque.  In the attached, the upper part of the shoulder (torso surface) has no cutout opacity map; the lower part of the shoulder (arms surface) has a cutout opacity map which is an entirely white JPEG file.  I would expect the two surfaces to render without any obvious border between them.

I have tried RGB mode and grayscale JPEGs; I have also tried PNGs.  I have tried characters that use the PBR Metallicity/Roughness model and ones that use the PBR Specular/Glossiness model.  All give the same result.

I can't figure this out.  Is this a 'feature', a bug (in which case I will report it), a mistake or a misunderstanding on my part?  It's a bit of an obstacle to making a 'window' in the skin to show another surface underneath!

CutoutWeirdness.jpg
640 x 721 - 309K

Comments

  • barbultbarbult Posts: 24,844
    edited February 2019

    I think adding an cutout opacity map essenially sets thin walled on and you lose SSS.

    https://www.daz3d.com/forums/discussion/250306/iray-uber-shader-subsurface-scattering-with-cutout-opacity-map

    Post edited by barbult on
  • andya_b341b7c5f5andya_b341b7c5f5 Posts: 694

    Thanks for the information, though it is bad news.  Seems very limiting - you can't expect good results from cutout opacity except on things with no real thickness.  I don't see a way to workaround this 'feature' to achieve what I want.  I could delete some faces to reveal the surface underneath, but I would like the edges to look more 'organic' i.e. less straight line-y.  I can 'do' a geograft, but have yet to figure out a way to get them to follow a full body morph correctly.

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