Multimatte and Affect all channels

[Raven]

I would like to get the affect all channels info for reflection and refraction in the multimatte, but I don't want it to affect the alpha.
Is there any way to do this?
I have also noticed that it take about 5 times longer to render when Affect all channels is on, is this normal.

Any ideas would help. Thanks

[Zdravko.Keremidchiev]

I do not think you can do that in one pass. What do you want to achieve, maybe there is another way?
Also I can't reproduce the slow render time issue with all channels set. How many render elements do you have? Can you attach a simple scene?

[Raven]

Hey Zdravko

Unfortunately I can't post files, I'll see if I can recreate it in another setup when I get a chance.
Basically I would love it if we could have an option in reflection and refraction that is affect Multimatte Channel.
So the material behaves as Color only, but the Multimatte has mattes for the reflections and refractions.

[Zdravko.Keremidchiev]

It will be very helpful if you could provide a simple scene.
Also we'll take your suggestion under consideration, but generally we restrain from adding additional options for isolated cases. Therefore it will be best if you could explain your workflow a bit more so we could come up with an alternative solution if possible.

[vlado]

I would like to get the affect all channels info for reflection and refraction in the multimatte, but I don't want it to affect the alpha. Is there any way to do this?

Not for the moment, unfortunately. There is a feature request to be able to specify which channels should be propagated through reflections and refractions in this way, but we haven't gotten round to that yet.

I have also noticed that it take about 5 times longer to render when Affect all channels is on, is this normal.

Probably. Propagating the render channels does require additional work from the renderer.

Best regards,
Vlado

[Raven]

Thanks Vlado