64 Channels In Nuke, Per Loader Or Overall?

[thedott]

Hi, I'm trying to wrap my head around Nuke and am wondering about the 64 channel workflow. I might have exr loaders that have up to 12 channels in them. If I comp several of these loaders on top of each other, does that mean 12 + 12 + 12 and I eventually reach the 64 channel limit? I'm new to Nuke so sorry for the nubie question. My experience is with After Effects and Fusion.

Barry Berman
3Dmation Visual Effects

[user_deleted]

Hi Barry,

the 64 channel limit is per script not per node. Once you create a new channel (or use one of the default ones) it is merely an empty container for pixel information that is available script wide for each node to store output pixels in.
If ten different nodes have different pixel information (i.e. mattes, images...) in the same channel than your still only using one channel.

Some people are under the impression that you have to create a new channel every time you want to store a new effect mask along with your rgba image but you don't. It's be like smashing your glass after having a beer and getting a new one out of the cupboard every time you want another one

Channels can be reused by every node, in fact, I got into the habit of not even bothering with a new channel most of the time when I need a quick gmatte for a colour correction or such, I just hijack the uv channels for that (or the alpha if I don't need it downstream, i.e. on the bg layer).

hope this helps.

cheers,
frank

[thedott]

Ooh, this makes me think of how these channels would be treated after merging. For instance, when we have an exr with 5 channels (to keep it simple). RGBA and Z, once we do A over B merge, is the 5th channel, the Z pass also merged too. I can see this being an advantage for some channels, but on others being not so, ei, UV, or vector data. Does that make sense, they merge? They don't create extra channels?

Barry Berman
3Dmation Visual Effects

[maya-man]

QUOTE(3dmation @ 05/04/07, 07:20 AM) [snapback]265410[/snapback]
Ooh, this makes me think of how these channels would be treated after merging. For instance, when we have an exr with 5 channels (to keep it simple). RGBA and Z, once we do A over B merge, is the 5th channel, the Z pass also merged too. I can see this being an advantage for some channels, but on others being not so, ei, UV, or vector data. Does that make sense, they merge? They don't create extra channels?

Barry Berman
3Dmation Visual Effects

Hi Barry,

Good to have you round here. Maybe you could do an AE-Nuke mocon script?
If I understand your question correctly, in the Merge node, Nuke has explicit controls as to what channels you want to be affected, the default is rgba.
Out of curiosity, what renderer are you using to get the multiple EXR channels?

Cheers,

Michael

[lebedev2]

I would like to know this as well. currently I am using mental ray to render my exrs out of maya. What I have not been able yet to fully grasp is how to use either frameBufferWriter or ctrl_buffers to output a single exr with all my passes. There is a tool set called shaders_P which allows you to render out to a single exr but you are stuck only using the p_megaTk shaders.

I think as a general note here any workflow information on how people are prepping render's for NUKE would;d be interesting.

S

[thedott]

QUOTE(blur1 @ 05/04/07, 03:19 AM) [snapback]265442[/snapback]
Hi Barry,

Good to have you round here. Maybe you could do an AE-Nuke mocon script?
If I understand your question correctly, in the Merge node, Nuke has explicit controls as to what channels you want to be affected, the default is rgba.
Out of curiosity, what renderer are you using to get the multiple EXR channels?

Cheers,

Michael

Hi Micheal, as a matter of fact, I'm in the process of doing MoCon for nuke right now. I need the tool personally, so I was planning on releasing it for others. For people that have already bought through toolfarm, it'll be a free upgrade, and I plan on having the same toolset in both AE and Nuke, but the Nuke tools will probably take a bit to get to the same level. I'll release in stages.

As for what renderer, I'm at Blizzard Entertainment (Cinematics). We've been primarily 3DS Max/Brazil, but are soon moving to Maya/RenderMan, yay! I think I understand the 64 channel flow now. It's easy for the channels to add up, but you just gotta know where to trim the channels you don't need, pretty easy really.

Barry Berman
3Dmation Visual Effects

[user_deleted]

Nuke has explicit controls as to what channels you want to be affected,
in addition to that it good to keep in mind that any channels that are not involved in te merge operation are passed through from the B or 0 input. So always make sure you get the right A and B input hooked up. Most of the commonly used operations (i.e. over, in, out) have countrparts to make it possible to swap A nd B pipes (i.e. under, mask, stencil)

the multi channel approach certainly requires a little more management/organization.

Hi Micheal, as a matter of fact, I'm in the process of doing MoCon for nuke right now.
that's great news! You know where to find your beta testers

cheers,
frank

[tomc]

QUOTE(blur1 @ 05/04/07, 01:19 PM) [snapback]265442[/snapback]
Out of curiosity, what renderer are you using to get the multiple EXR channels?

Cheers,

Michael

we are using nuke.....?!
we have to use multiple renderers so..... we can set up every channel/mask/layer in maya with our tool....
on the renderfarm, every maschine render all layers/channels in sperate files to the local tmp folder and after the frame is done,
the renderscript call nuke and a nuke-script build a exr with all rendered layers and send the final exr to the server....
its much easier to write shaders/buffers for every renderer.....

[maya-man]

QUOTE(schwungsau @ 05/15/07, 06:25 AM) [snapback]266108[/snapback]
we are using nuke.....?!
we have to use multiple renderers so..... we can set up every channel/mask/layer in maya with our tool....
on the renderfarm, every maschine render all layers/channels in sperate files to the local tmp folder and after the frame is done,
the renderscript call nuke and a nuke-script build a exr with all rendered layers and send the final exr to the server....
its much easier to write shaders/buffers for every renderer.....

Yes, that's a good idea...I could render all the passes to rgba float tiff and not have to worry about wether the 3D renderer can support exr the way I want. Float tiffs are huge files but can then be trashed once you've rendered the layered exr sequence from Nuke.