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Ogunzinho

The most basic C4D Multipass Q'tn Ever!

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HI

 

I've burned a couple of days and have had enough with tweaking nonsense and reading MAXON's help files.

 

C4D R19.068

Multipass to 32 bit .EXR files with the correct compression etc. All separate files, not a multiple EXR.
No Straight Alpha.

 

THE MOST BASIC C4D MULTIPASS QUESTION EVER:

 

If I select a MultiPass with 'Add All Image Layers' and then A/B between the 'Image' Rendered by C4D and the 'MultiPass' Rendered by C4D - using every available channel - the results look NOTHING LIKE EACH OTHER. Surely with every channel offered, the composite should resemble the Beauty Pass to the naked eye?

 

The differences are so huge as to make them different scenes, in terms of lighting, shadows, and especially alpha information within the scene.

 

WHY IS THAT?

The MultiPass system is basically a fancy tool that ^%@!s your renders, unless ludicrously simplistic and intending to get out of 3D ASAP and into AE or Nuke etc.

Am I missing something? Without even going from C4D to a compositing program, without even thinking about Linearized Work Flow or colour profiles, C4D's own picture viewer reveals that your composites cannot possibly match your beauty shots, the shadows and lighting are WAY WAY WAY different, and cannot be 'tweaked' to even marginally resemble the main pass.

What The Actual Fudge?

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  • Seriously? Nobody can answer this question?

    How do you get multipass renders to look anything like their Beauty pass composites as rendered by the standard renderer?

    Nobody knows how, or why they are so different?

    MAXON, anybody, any compositors, anyone?

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    Chill out dude - people are busy, and it's only been up a few hours. I'd give it a couple of days...

    You could profitably use the intervening time to search the site and see if you can find the various posts where this has been asked and answered before...

     

    CBR

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  • I'm pretty much resigned to it being a mess at this stage - didn't mean to come across impatient, just I saw '15 views' and no replies and thought 'Blimey!'

    It's nothing at all to do with exterior compositing workflows or color profiles - C4D's own render engine can't recreate a beauty pass from it's own multipass system (in R19).

    Looks like R20 has added 4 extra MultiPass channels - Direct Diffuse, Indirect DIffuse, Direct Specular, Indirect Specular - which *IF* you use PBR materials and PBR Lights, can be additively composited to recreate the C4D beauty pass, as described here:

    https://help.MAXON.net/us/#DRENDERSETTINGS-RDATA_GROUP_MULTIPASS
     

    From the horse's mouth: "With the Multi-Passes that were added in Release 20 it’s possible to correctly additively assemble the finished rendered image from individual Multi-Passes. This was not possible with the previous Multi-Passes." [Emphasis mine]

    So it's only really been A Thing (being able to accurately recreate the Beauty Pass) since R20, which I still don't have (or rather, have this huge project in R19, and will damn well finish it in R19. I've already learned that particular lesson, LOL. Never upgrade in the middle of a project).

    So I doubt anybody has had any success with it prior to now, and I promise you I've been hoovering up threads and replies looking for some succor or comfort in my smh amazement ;)

    Possibly trying the Material Channels might yield different results (closer? further? I've lost the will to live over the last 2 days, so can't be bothered with more experiments), but will probably frame this little nugget I discovered in the MAXON literature and keep it handy for future reference - it's tucked away in the MultiPass text that deals with Reflectance and Specular Layers if you choose either/both of those for your Multi-Pass:

    " Also note that, for internal reasons, the sum of the layers will never represent the composited image exactly."

    Seems like that's just the way this particular cookie crumbles, though if anybody here knows any different I'd love to know workarounds / Material Channel options / Prayers and ritual sacrifices that have worked for you.


    Cheers

    Daniel

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  • Just gotta pipe in, I've blown another few hours scouring this site, and I haven't found a single thread anywhere where anybody just fronts it and admits the plain facts:
    You can't get an accurate beauty pass render from C4D multipasses, the tech just doesn't work that way, without HUGE caveats and restrictions, special passes, and major limits, IF you are up to date with latest release, R20.

    I feel this should be printed in BOLD TYPE in the introduction to any course / article / tutorial on multipass compositing from C4D, because nobody really has the time to experiment like I just have, or, indeed, "...search the site and see if you can find the various posts where this has been asked and answered before...", because I can't find this info anywhere else on this site, and all the tuts and online resources just hit you like it's a groovy way to have a lot of control over your render (as if you have any idea what that really is until you separate the passes - YOU DON'T!)

     

    My two cents.

    Again, if any compositor or experienced render specialist knows any tricks or workarounds, or indeed if anyone can find a thread I've missed where this has all been revealed, I'm all ears.

    Cheers

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    The questions is, why not just work with all necessary Multi-Pass layers enabled already from the start?

     

    If I understood you correctly the problem is that Single-Pass and Multi-Pass renderings inside C4D already look different. So why not just use Mulit-Pass from the beginning and adjust your lighting and materials according to that?

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  • Yeah, but then you always get to eyeball the Image Render, and *it looks how I want it to look*. The Multipass renders are clearly inferior / need a lot of tinkering to get them to approximate the look required and that aoppears every time I render to viewport or picture viewer.

     

    Plus: Filesizes! A well rendered beauty shot that just needs tweak on shadows, or lighting, shouldn't really require a dozen 10mb extra files per frame just to get close in your composite.

    The idea of AOV's is to give you control over the rendered image so later decisions can be made / adjustments to components in context of other scenes without re-rendering. If the rendered image looks one way and the AOV's cannot be combined to recreate that exact look, then they are a different set of tools altogether - still useful, but definitely different, giving you control over a *different* image than the one you have been working on - close, but no bananas :)

    I guess I had a certain expectation that the rendered image is hiding behind settings I'm unaware of, or boxes that need checking / unchecking. It was a fairly draining experience trying everything under the sun, researching endless past threads, only to discover that "for internal reasons" (made me LOL) "the rendered image and sum of the composite will never be exactly the same", and I could have saved a lot of headache if I'd known that from the get go.

     

    Many, many historical threads of this type that always dwindle into "Me too!" and shrugs, with no answers or definitive outcomes.

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  • Quick update, as I'm a tenacious fool and WILL NOT LET IT LIE!

     

    I've discovered that a bug was introduced in R18 which (as far as I can tell) has still not been ironed out in R19 and will DRAMATICALLY change your renders if you don't fix it up when doing Multipass rendering:

    Lights in cloners cannot properly interpolate intensity. To fix this, you either have to add some keyframes (apparently, I haven't tried it yet) OR  (and this one I tried, and it works and makes a big difference) make your cloner instance editable, so you end up with real lights, not cloned versions.

    This has vastly improved the A/B similarities between Image View and Multipass in my case, though there is still some weirdness with the Ambience channel not correctly reading a VIsibility tag and thus leaving textures with luminance channels active rendered completely opaque when they should be at just 15%. Since they are contributing to GI, I suspect this might be the last hurdle to hammer into submission.

    Anyway, I was miles away from suspecting a buggy cloner as the main source of enormous difference between renders, and have clawed 1 step closer to a satisfactory result!

    Infernal machines...

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  • From the Sublime to the Ridiculous.

     

    A peak of pure joy to a new pit of bleak confusion.

     

    Glow, my dudes, is a massive b'stard. Having gruelled through some more threads, it turns out that Glow (Advanced Render, not material channel) is notorious for not rendering properly as part of a multi-pass collection. I have a hefty Glow in my scene. So, I rendered all but Glow, then just Glow as a totally separate pass.

    Voilá. The Image Pass can now be recreated by Compositing the multipasses, rendered separately, with the Glow set to 'Add'.

    But wait. THE PLOT THICKENS.

     

    To check that the two could be A/B'd in the Picture Viewer to eyeball any differences, I quickly ran an new beauty pass, with MultiPass completely disabled. Simple, nice and quick and neat, let's compare.

    Hahahahahahahahahaha.

    The renders are completely different. As in: An Image render with Multipass active looks vastly different to an Image view of a render without Multipass enabled. Same view. Not that the Image view and the multipass view are different - there's now now Multipass view, it's de-activated. And now the main render is completely different.

    Try it. Take any scene you have with Post Effects and render it.

    Now activate Multipass - you don't have to select a single thing, just tick the Multipass box and leave everything else blank.

    Your render is different.

    I have to confess, I'm now utterly, completely lost.

    This must be a colorspace thing, but why do the two beauty passes of an identical scene, one with multipass enabled and the other not, look so completely different?

     

     

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    Well, we certainly can't say you haven't put the effort in :) Even though it's not a problem that particularly affects or bothers me I am grateful that you are investigating thoroughly and reporting your experiences - this can only help the situation improve in the future. I too have contacted MAXON about this issue - last time I tried to render Hair with Multipass I hit brick walls all the way, and even MAXON, though they did enter a dialogue and try to be helpful, were also vague and fuzzy about why that might be, and neither them or I ever found the reason these things looked utterly different in beauty and multipasses. I have been quiet in contributing to this thread because a) I don't consider myself expert enough in that area to absolutely KNOW what I should be getting out of a multipass, and b) because the amount of evidence available makes me suspect there isn't a solution to this in your version, although I certainly don't know that for sure either.

     

    But anyway, thank you for your continued efforts to get to the bottom of this, and very best of luck with your ongoing investigations !

     

    CBR

     

     

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  • LOL, cheers dude.

    At this point, though the project isn't commercial, I've crossed every deadline / commerce / mental patience barrier I have, so in a similar vein I'm gonna call it here, and just accept that compositing out of C4D is a messy, spit-n-bluetack affair, and not some elegant magic show as described on the tin. With a bit of brute force and some feathered masks, I can get a reasonable outcome here. It cracks me up that for my particular scene, in order to end up with a well post-produced .PNG frame of about 4Mb I need something in the order of 24 32-bit openEXR files totalling something like 90Mb per frame....My mind wanders to productions like 'The Hobbit', done at 60fps at 4k resolution, and I imagine warehouses filling the Outback with Hard Drives full of compositing layers. The size of a small town.

    Immediate Plans: Ditch Standard / Physical renderer for Redshift, and never look back!!! :lol:

    Bring it on!

    If at some magic point in the future I ever discover what's up I'll be sure to check back in to the thread. Incidentally I tweeted Chris Schmidt from GSG the other day, but no reply as yet!

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  • LOL

     

    Don't ever feel bad about struggling with this stuff.

    One of the shining brains responsible for much that makes C4D great also can't quite pin it down!!

    Chris Schmidt, from GreyScaleGorilla adds...

     

    Screenshot_20190708-191515.png

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