Hello,
I currently have a scene with 4 different objects inside (see attached image).
I want a seperate pass for each of the cans, so that everything that belongs to one can (shadows, reflections and the can itself) is in one pass.

The goal is, to make a nice fade-in in after effects later, so every can appears at a different time.

I am already using AOVs and such (using arnolds cryptomattes), but up to now I'm just able to get the seperate cans, not the corresponding reflections and shadows on the others cans. Which however I need for a proper fade-in.

Are there any tips and tricks you could share to achieve this?

Thanks

It's simplest to render each element separately, with the objects to appear in reflections/casting shadows set as phantom.

If that's not an option, a fairly simple way would be to have a unique shader on each can that exports its beauty pass ‘Cf’ with a unique name. Then add an image plane for each new beauty export.

To get more granular control than that, such as which can's reflection and what not, look into LPE's. LPE are powerful expressions for describing paths light takes in a render.

Thanks for your quick response.
In the meantime I tried the first and second of your suggestions, but I seem to miss something here.

I primarily set the right can to phantom, and it does as expected. But how does that help me, to get the reflection only? Thought I could use the indirect pass only, for the reflection, but that doesn't seem to work either.
I attached some images for illustration purpose.

I secondly tried to make every shader of every can unique. I did so by creating an unique attribute on every can and then made an AOV out of it in the shader network. But only thing I get, when adding it as an Extra Image Plane, is a black & white mask.

Would you be so kind and elaborate a bit more of your workflow or could you recommend a tutorial that covers that topic?

I don't think it's possible to split render passes that way at least not without generating a lot of AOVs in multiple renders

think of it this way you need at least 5 base renders (4 cans 1 set)
for each of them you have following problem:
e.g. can 1 reflects all other cans, so even if they are phantom, you need to have LPEs that split the contributions per each other can and also LPE that contains the rest (so far so good)
but even if you do that, what is gonna contribute to the same part if either of the cans is not visible? since secondary rays didn't see past the phantom can, that part will just be darker
then you may need to be rendering non-occluded render layers and contribution masks, just to blend in correct portion of the non-occluded environment reflection, but that will not work as well if there are 2 cans in a way, so you can see it's just getting more and more complex …

but if you know the order in which they are appearing, just render 5 renders
1. just set
2. set+1st can
3. set+1st+2nd can
4. set+1st+2nd+3rd can
5. set+all 4 cans

then reveal as you please as long as the order is the same

Thanks for your explanation; this is really appreciated.
Thought this could be done easier, but it absolutely makes sense this way.

I know the order of appearence indeed, but actually I wanted a bit more than a simple fade-in. Rather the idea of a glitchy/holographic fade-in came on my mind. Seems that this means a bit of masking in After Effects, right?
Or give up my plans and stick to a simple fade-in (or do the glitch in Houdini itself).

Either way thanks for clarification.