loosing reflection in alpha

[lukx]

original render

this is generated alpha :

as you can see there's no reflection detail in it so when I compose render with alpha and add black background I'm receiving different result that original render.
comp: missing reflection detail:

[joconnell]

The final render you're showing there - is that the main beauty or one of the elements?

Do those extra pixels appear in the vrayReflection element or the vrayRawReflection element?

[lukx]

the first render is beauty.

I have to test if those show on rawreflection ...

[joconnell]

It kind of looks like the type of random pixel you'd get in a reflection render element where the reflection is incredibly weak - in other words for those pixels, the reflections are contributing a tiny amount to the final rgb values of the pixels, and so vray's early termination has decided to cut off it's sampling early. I've seen very similar with various extratex renders such as when I render a vray dirt map for a contact shadow. For areas of the image that are visible within the alpha channel, there's proper sampling and everything is fine. For areas outside the region of the alpha channel though, the sampling gets very very noisy and random, mainly as the alpha is going to remove them anyway, so vray is seeing them as unnecessary and cutting of sampling early. might be something else but it seems like a lot of those pixels are made invisible by the alpha anyway so it's little to worry about?

[lukx]

I think it also might have to do with using gamma 2.2

[vlado]

Did you enable reflections to actually generate an alpha channel (i.e. set the "All channels" option for reflections to "Color+alpha")?

Best regards,
Vlado

[lukx]

Yes I did but then everything got even weaker when I'm saving to png and drop black background.

[lukx]

really can't get the concept of this. even when I render vrayRawReflection to png and add it on top of basic render it still doesn't' look like straight render from vray.

here's how things look like in vray frame buffer:





here are files ice.zip

I'm attaching files maybe someone could show me how to compose it to get the result as vray frame buffer render

[Zdravko]

Would it be possible to send us the scene to: support@chaosgroup.com?