Material ID or another method for post selection in AE ?

[stevesideas]

Hi guys,

I have an animation that is going to have to go to post (aftereffects cs4) for adjustment and added effects. I was wondering. If I want to just have some particles and an object that I need to apply a glow to and maybe a lens flare, would the best method of selection for those objects be material id, or would you just do a seperate pass using alpha for the particles and object ?

If you would use mat id, how do I use that in AE ?

[sv]

multimatte man
In AFX use Channel > set matte to isolate your selection

[stevesideas]

ok cheers for the reply, but would I have to render the mat id's to seperate sequences, or the matt selection would include all of the id's for the mesh and the particles whereas I need them seperate....I dont think I stated that..

[rivoli]

if it's only for particles and another object, you won't need more than one pass. from the multimatte element you can extract up to three mattes, one for each rgb channel that is.

[plastic_]

VrayWireColor is maybe another (simpler) option...

[rivoli]

but it won't give clean mattes to work with. it may not be as straight forward as the wire colour to set up, but it's going to be so much better later on when doing the compositing.

[lllab]

normally i would say the object ID buffer is perfect for AE. but in vray it is not anialiased.

what i always wondered is how users use the object ID buffers, asit is not anti aliased.
i understand from vlado that this is wanted for apps like nuke

but doe users here use this also with after effects or photoshop?
to my thinking this should be with anti aliasing then. or are there ways to use this without AA?

cheers
stefan

[plastic_]

for animations it has do be properly AAed of course.
with photoshop, the wire color is good enough for me. you can always refine the selection edge in photoshop if there are some jagged edges. but still better than using the lasso tool

[instinct]

well Multimatte does just that. 3 mattes per layer (RGB) that are properly antialiased and bound to object IDs or (if you prefer that) material IDs.

By seperating the mattes to RGB only you can get pixelperfect mattes wich you can't with wirecolor and alike.

You can add as many MultiMattes as needed and render it all in one pass.

Kind Regards,
Thorsten

[dejaVu]

Yep, Multimattes in a multi-layered exr is the way to go.
Add as many of you need and use EXtractoR in AfterFX CS$ to extract the element you need.

[stevesideas]

Ok, ive not used multimatte element before...will see how I get on with it.

Thanks for the tips.

[muoto]

multimate works perfectly. I use it all the time with some presets for materials i always need to work on in post-prod (some reflections on glass, or chrome for instance) where i use the multimate as masks on the reflection pass.
All this in Nuke, it works great!