Affect alpha channels in Reflection!

[RenderGuru]

Is it possible that the ammount of reflection thats in the RGB channel is also in the Alpha channel ?

At the moment, as much as you bring in the reflection as much the alpha of the object gets more intense. so at full reflectivness you will get a full opaque alpha. (see attachments A-C.jpg) BUT what you probably want is that only the reflections are shown in the alpha with its correcsponding Luminace value....
Is there a workaround or can you just add the "Affect Channels dropdown" in the Reflection Section as well..... please! (see attachment wanted.jpg)

[RenderGuru]

nobody any suggestions? please?

[judderman]

I posted a question about this in an old thread but nobody responded so I had to do some digging. I've had some success using SP5 and the reflection occlusion option in vray dirt. Well, I'm assuming it's new because Vlado specified SP5.

Then using the vray extra tex in the render elements having the vray dirt texture linked in there, I was able to get a black and white matte to render of a reflection pass. Took a good bit of fiddling to get it right, but it looked good in the end.

It'd be soooo much easier to just have a separate render element to do this automatically though

[judderman]

I should say what I was trying to achieve first of all and why I needed a reflection pass.

I was compositing a vehicle on a photo of a wet road, so I needed the reflection to have an alpha channel. Vray dirt on the ground with reflection occlusion option, render extra tex then in render elements.

Regards,

Judderman.

[RenderGuru]

Thanks for the reply, can you post a testscene for me please.... I am still wondering why there isnt the same dropdown box like in the refraction slot. Or a checkbox like:
"get alpha from RGB" that would solve this....

I need this becaue I have to render a transparent shell of a pill which has some micro material in it. so the Outer hull of the pill is like glass, showing reflections but noch much more. See Attachment.
I know I can render a separate pass but It is always great to have as few passes as possible....