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Multimatte Madness - Halos are abound
show user profile  9krausec
Hey everyone! I have a quick question for all of ya'll.

I'm starting to rely more and more on the Multimatte vray pass to create masking for comp work in AE. However, When I apply a shift Channels effect to pull out one of the 3 channels (RGB), I end up getting a weird halo around the edges.

Working in 32 bit space n' all that. How would I go about fixing this? Image below-

 photo 1_zpsk6d4onqe.jpg

 photo 2_zpseqhpmvoo.jpg

I know I'm getting into the nitty gritty here.. But there is not a tight "seal" with my multimattes. The resolution is only 1280x720 and antialiasing is on for the render element.

Any ideas on how not to get this effect?

Thank you.

- Portfolio-

read 583 times
4/2/2016 12:10:59 AM (last edit: 4/2/2016 12:11:17 AM)
show user profile  Garp
I remember getting edge artifacts with multimatte but that was in prehistorical times (vray 1.5 I think).

If there's an option to antialias on a per channel basis, it should help.
Otherwise, just kill the red channel to black in post. I can't think of anything else.

Ideally, I believe you shouldn't antialias the mask(s) nor the elements you're masking, since antialiasing 'blends' things. You should only antialias the comp.
(Someone with fresher neurons might step in.)

read 569 times
4/2/2016 4:15:34 AM (last edit: 4/2/2016 4:23:13 AM)
show user profile  9krausec
^Garp, thank you. I didn't know you should AA the actual element passes. I guess I'm still not sure how that makes much sense (unless it's applying a double amount of AA).

If you AA the beauty, should you be doing the same thing to the elements? Multimatte for instance, used as a masking pass. If the Beauty object has nice anti-aliased edges, then wouldn't you want the Multimatte of that object to also have AA'd edges?

I'm not doubting you know what you are talking about, but I still think I might not be understanding the why/why not factor in anti-aliasing the render elements.

- Portfolio-

read 520 times
4/5/2016 10:10:59 PM (last edit: 4/5/2016 10:10:59 PM)
show user profile  Bolteon
After Effects.

-Marko Mandaric

read 517 times
4/5/2016 10:19:24 PM (last edit: 4/5/2016 10:19:24 PM)
show user profile  9krausec
Thanks for the input guys. I'm still experiencing the issue so I made a short video to demonstrate what exactly I'm on about.

So the deal for this project is that I didn't want the floor to affect the alpha. I wanted the hero object to be the only thing affecting the alpha for obvious color correction reasons. I put the floor on a multimatte so I still had access to it.

Now I find myself wanting to generate a mask for just the black background so I can add a post background to the animation. Still getting a nasty halo and I have no clue why. Any help would be appreciated.

and my project settings-

 photo sett_zpshu6rnz86.png
Thank you for any input.

edit: As of now I'm just going to re-render all of my sequences with the desired alpha. It's a fix, but this issue should be avoidable with the output I have (or at least I would suspect that to be the case.)

- Portfolio-

read 469 times
4/11/2016 1:06:23 AM (last edit: 4/11/2016 1:21:38 AM)
show user profile  FX
Can't help, only to say I have exactly the same issue, my fix was to make all other objects invisible to camera, 32bit exr comes into PS with squeaky clean outlines.

I use PSD manager for my mattes so this must be a Vray issue, no AA either btw.

read 440 times
4/11/2016 12:08:30 PM (last edit: 4/11/2016 12:08:30 PM)
show user profile  Bolteon

-Marko Mandaric

read 427 times
4/11/2016 3:30:44 PM (last edit: 4/11/2016 3:30:44 PM)
show user profile  FX
read 422 times
4/11/2016 3:44:16 PM (last edit: 4/11/2016 3:44:16 PM)
show user profile  9krausec
Bolts, I think I agree with you. Going to install that learning edition of Nuke on my new build right away. Plus a little birdy told me you can import alembic into Nuke which makes me super f*cking excited.

- Portfolio-

read 420 times
4/11/2016 4:03:03 PM (last edit: 4/11/2016 4:03:03 PM)
show user profile  FX
I just fixed my halo issue by rendering the matte pass with a self illuminated material in the scene override slot with GI turned off... no AA.

Zero halos and precise selections. :)

Don't know why but Bolts 'Adobe' comment triggered a distant memory of something similar a few years ago re matid passes, the solution was to use self illuminated materials, also works for mattes.

I use PSD manager but Vray has a similar 'Render Mask' feature in the Image Sampler rollout..useful too.

read 384 times
4/13/2016 6:44:32 AM (last edit: 4/13/2016 6:48:18 AM)
show user profile  9krausec
Thanks the the advice FX. I think I've found my true calling-

Edit: Now I just need to wait for it to come to Vray. :) I've never heard of this Guerilla Render so I need to research up on it a bit.

- Portfolio-

read 365 times
4/13/2016 4:36:16 PM (last edit: 4/13/2016 4:39:18 PM)
show user profile  FX
I also think it's time to drop PS as a comping tool, and move onto something bigger and better , just too many damn issues with it.

Apparently the 'defringe' tool fixes the halos as well, because the edges are premultiplied ?, anyway I'll stick with the self illum fix until I move to Nuke.

read 363 times
4/13/2016 4:58:49 PM (last edit: 4/13/2016 4:58:49 PM)
show user profile  Bolteon
V-Ray supports EXR 2.0...

-Marko Mandaric

read 356 times
4/13/2016 6:41:13 PM (last edit: 4/13/2016 6:41:13 PM)
show user profile  9krausec
Thanks Marko. Good to hear. <3 Vray

- Portfolio-

read 351 times
4/13/2016 6:54:06 PM (last edit: 4/13/2016 6:54:06 PM)
show user profile  FX
So working in 16 from Vray is exactly the same as working in 32 and converting to 16 in PS. ? in no difference in resultant colour info ?

read 338 times
4/13/2016 8:01:11 PM (last edit: 4/13/2016 8:01:11 PM)
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