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Rendering with Arnold in CINEMA 4D using the C4DtoA plug-in.
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Alpha Channel texture on glass object

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Message 1 of 5
Gautier_Dalivoust
1781 Views, 4 Replies

Alpha Channel texture on glass object

Hi, I’m having difficulties to put a transparent texture (a logo) on a glass object (a bottle). I’ve been looking at other people explanations and your tutorials (add a C4DtoA tag and unchecked the « opaque » button), but when I superpose the 2 textures on same object (outline logo over glass material), it shows only logo… I cannot see the glass below. Please see attached image. I’m a bit surprise how it seems complicated to do such a simple thing… Can you please let me know the trick ? That would be super helpful Thanks a lot !

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Message 2 of 5
zenop
in reply to: Gautier_Dalivoust

The way these things usually are done is by creating a layered shader (aiMixShader), you've got much more control that way.

Base material is your glass, then create another material for the logo and use your current opacity mask in the mix parameter.

Message 3 of 5

Thanks for the tip,

however the problem is when you mix 2 materials like that (let say "blend / 0.5" )

it displays both materials at 50% opacity...

Please see attached screenshots (Logo material on top of Glass material) :

1) Mode : Blend / Mix : 0 > See only the logo

2) Mode : Blend / Mix : 0.5 > See both but both are 50% transparent

3) Mode : Blend / Mix : 1 > See only glass

I'd like to keep logo opacity to 100% (not transparent) over the glass.

I'm amazed how such simple thing is such tricky...

screen-shot-2018-03-08-at-103542.png

screen-shot-2018-03-08-at-103557.png

screen-shot-2018-03-08-at-103605.png

Message 4 of 5

Use the alpha channel of the image for the mix, or another image shader if you have a separate alpha.

1086-mix-image-shader.png

If you use an uv_transform to scale and position the image, it's a bit more tricky, because the color widget does not have an alpha channel, and so the Wrap frame color is exported with alpha 1. So you have to use a float_to_rgba in the Wrap frame color.

1087-mix-uvtransform.png

Hope this helps.

Message 5 of 5

Thank you Peter !

Yes I just found about the Alpha channel into the Mix, I get it now !
And right, when I projected the texture as cylinder type on the cylinder object without "tile" (I want only 1 logo on front) and scale to the desire size, it render black outside the texture area...
I managed to do the trick by adding another glass material on behind to fill the space but I will try your way, thanks for super helpful tip !
(still amazed by how complex it is just to do that 😮 )

Thanks again for your help !!

screen-shot-2018-03-08-at-184351.png

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