Refraction rendering opaque

[fabrice_barbey]

Hi super_noob question I guess :
I have a 1 dome light, 1 teapot with a glass VrayMtl on it.

But the teapot alpha renders fully opaque.
I mean the render looks gooid but its alpha is pure white making it impossible to comp.

The alpha should appear partly transparent.
Why is that?

(Same thing on Vray and Vray GPU)
Cheers

(Vray 6 2.1 + Max 2025 + Fusion)

PS : there are hundred of post about refraction and alpha in this forum but couldnt find the answer

[dlparisi]

You need to have the refraction "Affect channels" set to "Color+Alpha".

[fabrice_barbey]

Thanks !
(I dont really understand this default setting choice but it works now )

[fabrice_barbey]

Now another problem arises.
I work on a furry tail made of hair cards (so a lot of transparencies).

Rendering it with CPU seems faster for a better quality (default settings).
My problem is :
For CPU the alpha and normal elements are wrong, way too contrasted...why should that be?

[hermit.crab]

Does the quality improve if you increase the Max transp. levels (Render Setup> V-Ray> Global Switches) to f.e. 100?