how to render multiple layers/buffers within openexr images?

[Blur1]

It seems to me that for end users not working in big studios, EXR output still seems to just be RGBA. How about Maya 7? Sure would be nice if it output multichannel EXR regardless of what renderer you chose. Or even mixing multiple renderers into one EXR file, with channels based on your render layers output.
What about the Renderman for Maya plug-in?

[1armedScissor]

Mental ray supports custom framebuffers that will allow the user to output multiple images to one file. Do a search here on cgtalk on framebuffers in the maya render section and you'll find a bunch of stuff. There's even stuff available here for download to help you out.

[rendermaniac]

In RenderMan you just call all your secondary displays the same name and they should get put into the same EXR file. I haven't tried it myself but another guy at work has. You will end up with two images - your rgba pass and a second image with everything else. I don't think it's possible to put everything in one.

Also Nuke is the only program available that I know of that can access all the channels in an OpenEXR file. Shake is limited to 5 - rgbaz unless you write your own filein node - and even them you can't pass them through to other nodes. Any Discreet software is even worse (don't think they support EXR - at least not on Inferno). I guess Photoshop CS2 can handle it, but that wouldn't be too useful for animations.

Simon

[1armedScissor]

I can't do it myself but if your compositor of choice doesn't support openexr out of the box and you have someone at your disposal who has some knowledge of the compositors api/sdk then they would be able to get your compositing package to read any channels you write to the openexr file.

[Blur1]

Does anyone know if there is an efficient way of updating (re-rendering) a channel within a multichannel exr image? Or do you just have to render it as a separate standalone pass and replace it in comp?

[playmesumch00ns]

In RenderMan you just call all your secondary displays the same name and they should get put into the same EXR file. I haven't tried it myself but another guy at work has. You will end up with two images - your rgba pass and a second image with everything else. I don't think it's possible to put everything in one.

Also Nuke is the only program available that I know of that can access all the channels in an OpenEXR file. Shake is limited to 5 - rgbaz unless you write your own filein node - and even them you can't pass them through to other nodes. Any Discreet software is even worse (don't think they support EXR - at least not on Inferno). I guess Photoshop CS2 can handle it, but that wouldn't be too useful for animations.

Simon

Shake 4 lets you choose the channels you want from a multichannel exr doesn't it?

Personally I like the idea of packing everything into one exr, but I'm unsure still: if something screws up writing the file, then everything is screwed. If you're rendering to seperate files you can still get something useable.

Having everything in seperate files also allows you to be more selective about what you release to 2D, and that's especially helpful when you're moving stuff around between disks: you can be economical about how much data you transfer.

[Blur1]

Personally I like the idea of packing everything into one exr, but I'm unsure still: if something screws up writing the file, then everything is screwed. If you're rendering to seperate files you can still get something useable.

Having everything in seperate files also allows you to be more selective about what you release to 2D...

Yes my thoughts exactly (see my previous post). But surely that was accounted for? You're bound to want to update individual passes more than a few times. But I like the coolness factor of having the multichannel EXR, with proxies (although Shake 4 doesn't currently support 'em).

[gga]

Anyone tried or know how to render out open exr images in MR or Prman with these multiple passes/buffers within a single exr image? Thanks for your help in advance!

For mray, you can use my gg_exr output shader (available as a demo shader part of mrClasses). You can then output each layer as a separate image or all of them together.
mrClasses is disted as source code only, but there are windows .dlls available on the net (just google for them).
You will probably want to disable mental images' own EXR (mi_openexr) shader in your maya.rayrc file if you are using a maya6.5 or later. Otherwise, you could run into conflicts, particularly if the two exr shaders use different versions of the exr library.

[WireFX]

You can try to take a look at air from sitexgraphics.

There is a multilayer example for PSD files included in the example scenes section. The OpenEXR displaydriver is supposed to work equally.

WireFX

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