[wimver]

I wonder if there is a solution for this situation:

I generally make product shots on white background (with very well kept secret of professional studio lighting setup )
but the client often asks for the alpha mask without the white background.
although rendering an extra image with alpha does not take that long, it creates overhead and it would be nice to render it in one go. I tried with the 'hidden from camera' option, but apparently it is not possible to hide an object from alpha mask.
or is there?

tnx
wim

[Mihai]

If you hide from camera though you won't get the background in the render. I'd just make a background in PS and reuse it. If you hide the background from camera it should hide it from the alpha as well. It works fine here.

[wimver]

Mihai,

the reason why I want to include the background is that I need the shadows cast from the model onto the white backdrop.
after that, I make an alpha mask without the backdrop, so the client can combine these in photoshop and modify or erase the shadow without affecting the model. also, the shadow can then be multiplied with a textured background if necessary.

wim

[wimver]

a button "hide from alpha" would be nice, and not too difficult to implement.

w

[zak]

The same could go for reflections. A reflection layer, so if you want to insert a boat on water, you can get the reflection in the water in a layer and then paste a background in PS.
In formZ we got a material called "Catcher" it works like a charm.

J