assembling raster passes

#1

Hi! i am trying to reassemble my nuke layers in Shake or Nuke, but can not seem to get the order correct. Is there something special i need to do to make it work? Any help would be appreciated!

#2

If you render a ‘multipass’ file, and save it as a .psd, vue will give you a photoshop file with all the layers you need.

I know matching a photoshop layer comp in Shake / Nuke is not completely trivial, but it will give you the correct order and blend modes of the various passes.

Hope that’s what you were looking for.

AJ

#3

it turns out there is a bug with the raster pass system in Vue 7.x. It does not render out alphas for the passes. And the specific layer that is giving me issues, the Atmosphere Gain layer even has a note in the docs about how a vue render will never look correct if multi pass is used because of Photoshops lack of additive layering. I know nuke and shake can do math so if i knew the math fucnction of additive i may be able to solve this issue.

#4

Many apologies - it sounded like you were asking a question that’s a LOT simpler to the one you actually meant. :blush:

Not sure what info you’re looking for, though. The ‘math function of additive’ is just an ‘add’ node, which both shake and Nuke have (and unlike photoshop, they get the maths right)… :shrug:

Or have I misunderstood you again?

AJ

#5

no worries, i should have elaborated better =D

i tried add but, it still gave me an incorrect result.
here is what i am talking about…
http://homepage.mac.com/oddgit/clouderror.jpg
and here is what it should look like
http://homepage.mac.com/oddgit/noerror.jpg
i may have to figure out how to generate a mask or something. Because that really wont work well for my thesis project. That errored image is what the .psd looks like, when you view all of the passes together, when you look at a full beauty pass, it looks like the second image.

#6

Upload the photoshop file, and I’ll have a look - I’ve never got a .psd comp to EXACTLY match the colour pass, but it’s always been pretty close (bar some anti-aliasing on the edges of leaves).

So error or not, it shouldn’t be that bad…

AJ

#7

here it is.
7mb
http://homepage.mac.com/oddgit/vuepsd.zip
I have been playing with the nuke layer settings on my comp, i have come close to getting a look similar to the one i get when i render, other then a really nasty matte line between the ground and sky.
Ultimately i want to build a gizmo that will make it easy to layer each scene in nuke, but i need to get past all of the strange quarks.

#8

Okay - I see what you mean.

If you set all of the ‘screen’ blend modes to ‘add’ (linear doge), in the photoshop file you get a result that’s CLOSE, but not identical. It looks like vue has done some auto-exposure adjustment on the colour image, which might account for some of the difference, but I can see why you aren’t happy.

I never realised that the ‘atmosphere gain’ pass would also include the information for any clouds that are in front of the landscape. That’s just lazy coding on eon’s part, though I can see why they might want to take this ‘short cut’. PITA for comping, though…

Maybe 7.4/7.5 will fix this, with the promised ‘alpha channels for clouds’, but that’s not very helpful for your current work.

So I would suggest a bit of a fudge workaround:

  1. Hide everything but the clouds/atmosphere, and render a colour image (image#1)
  2. Turn off ‘god rays’ and render again - this is image#2
  3. Subtract #2 from #1 (using a subtract node) to get the god-rays by themselves (image#3)
  4. Make a rotoshape / bezier mask for the ENTIRE cloud layer, incorporating the alpha channel for your mountains where necessary.
  5. Use this as the mask for image#2
  6. ‘Add’ image #3

Might need some tweaking - kind of posting off the top of my head here. But I hope you get the idea - trying to separate the ‘god rays’ from the low-lying clouds so you can comp/grade them individually.

AJ

#9

Yeha i saw the patch notes for 7.4/7.5 luckily they are letting students have it for free.
I did find workaround in nuke, but i have to deal with crazy mask lines now. With anyluck my nuke teacher will be able to figure out the correct combo of unpremult and premult, i am the worst at remembering the premult order.

#10

one thing i noticed is that the shadow pass is super noisy, is that normal? I thought my AA settings were rather high.

#11

It does tend to be pretty noisy / nasty - particularly if you’ve got motion blur of any kind. Vue seems to do some kind of B/W dithering in the shadow pass, rather than the smooth gradients you might expect. Don’t know why :cry:

Vue’s render passes are often rather odd (as you’ve noticed) - once all the passes are comped together all the information seems to be there (-ish), but not cleanly separated out in useful ways. Another bit of Vue weirdness, which eon may sort out when they get round to it.

I therefore don’t really use many of the render passes - and always find I need to paint over Vue renders in any case to get them looking right. Great for matte painting, a little bit useless as a production renderer…

Best of luck with your project.

AJ

#12

After a few exchanges with e-on they said that raster passes should be fixed in 7.4 including the lame shadows issue. Still sucks for me because i wont have nice stuff to show for my finals. But both my instructors that i am using vue on my projects for were understanding of the bugs. I am even turning in the nuke gizmo i built to layer the raster passes together and to comp in the other render pass, it even adds stuff like specular bloom and faked 2d/3d vector blur based on zdepth and the camera. =D It just looks rather silly because of the pass issues.

#13

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