Use Object ID to merge multiple Renderer 3D outputs

Hey guys, I'm trying to combine the outputs of various Renderer 3D nodes, with each of them focussing on a different object in my 3D scene, so I can give every object the render settings it needs.

I've set up individual Object IDs for all the objects and activated auxiliary channels in the Renderer3D node, ticking Object ID.

For one, I can select "ObjID" from the colour channel drowdown in the viewer, but the viewer remains black. Is there no colour representation for the individual object IDs?

Either way, I realised that - although you can't see the Object ID channel - it kind of arrives downstream, in the Brightness/Contrast node I set up to test the Object ID functionality. In the B/C node it does indeed allow me to isolate the changes in brightness or contrast to only the Object ID.

However, I would like to use the Object ID pass in a downstream Merge node, to combine different Renderer 3D outputs on an object by object basis. Activating the "Use Object" setting in the "Settings" tab of the Merge node has no effect.

Am I missing something? Something tells me that I would have to convert the Object ID pass into some kind of matte (either luma or alpha), but I can't seem to be able to achieve that.

Any suggestions would be highly appreciated

OK, a couple of really helpful people (above all "Goup") on Discord helped me find the solution.

First things first, you can use the CopyAux node to visualise the auxiliary channels as colour channels, like so:

CopyAux.png (64.8 KiB) Viewed 3010 times

But that didn't quite give me what I wanted.

Another option was then to use the Bitmap node and activate the "Object ID" option, like so:

Bitmap.png (63.97 KiB) Viewed 3010 times

This was super close, but unfortunately I ended up with an unsightly aliased line where the ground meets the transparent BG.

I then noticed that deselecting "HiQ" in the Renderer 3D node's Anti-Aliasing/Per Channel Settings/Enable Anti-Aliasing settings did manage to get rid of the jaggedy line.

Bitmap_NoAliasing.png (116.22 KiB) Viewed 3010 times

So this seems to do the job for now

However, in the end it's probably best to "divide and conquer" everything in 3D space feeding things into their respective renderers and omitting whichever objects aren't needed for specific passes. This way you get clean passes with just the right alpha channels you might need.

Something like that:

DivideAndConquer.png (80.67 KiB) Viewed 3007 times

With object ID passes that have hard edges I often use a matte node to blur and erode so the edges to match better.

Hi
In an ideal world , Fusion would build in the Cryptomatte plugin (currently only available as an input option as part of the Reactor suite) , which would give greatly improved object/material/asset masking with softer edges and easier options to mask all objects. If it was available out of the 3D renderer (and/or , even better, the new USD renderer..) it would improve quality of life for all involved in 3D/2D integration.
Goto https://github.com/Psyop/Cryptomatte/bl ... /fusion.md for more info.

I believe the Coverage channel contains the anti-aliasing information you need. I don't have Fusion in front of me at the moment, and I don't remember for sure about its use, but I think it's to be multiplied with a matte pulled out of the Object or Material ID. It's still not as good as a puzzle matte or Cryptomatte, but it's better than the aliasing you get from the integer ID channels.

With object ID passes that have hard edges I often use a matte node to blur and erode so the edges to match better.

Thanks a lot. Yes, the matte node does indeed sound like a good idea!

Hi
In an ideal world , Fusion would build in the Cryptomatte plugin (currently only available as an input option as part of the Reactor suite) , which would give greatly improved object/material/asset masking with softer edges and easier options to mask all objects. If it was available out of the 3D renderer (and/or , even better, the new USD renderer..) it would improve quality of life for all involved in 3D/2D integration.
Goto https://github.com/Psyop/Cryptomatte/bl ... /fusion.md for more info.

+1 on that one. Fusion still has a long way to go in order to compete with the 'establishment', i.e. Nuke and After Effects. But I can't escape its rough charms If I could, I'd do almost all of my mograph and comping inside Fusion, but there's always a moment when things either don't work or don't work as expected, when I'm forced back into the world of Adobe

I believe the Coverage channel contains the anti-aliasing information you need. I don't have Fusion in front of me at the moment, and I don't remember for sure about its use, but I think it's to be multiplied with a matte pulled out of the Object or Material ID. It's still not as good as a puzzle matte or Cryptomatte, but it's better than the aliasing you get from the integer ID channels.

Thanks Bryan! Fusion-wizard at work as always I'll check out the coverage channel as soon as my schedule clears up. Sounds promising!

[daniel.koch]

For one, I can select "ObjID" from the colour channel drowdown in the viewer, but the viewer remains black. Is there no colour representation for the individual object IDs?

There is, but the colour values of the IDs are likely too dark to see. Try turning on Normalized Color Range in the viewer dropdown, that should brighten things up.