Comments on: Label/Tag & Coverage passes – LabelExtractor

By: pryaneek

pryaneek — Wed, 30 Jun 2010 13:31:28 +0000

Когда же уже будет продолжение статьи? (о том как собирать + сетап для Fusion)

By: Sagroth

Sagroth — Thu, 01 Apr 2010 18:23:14 +0000

Если под “гребенкой” подразумевается отсутствие анти-алиасинга, то да. Как это вытягивать в композе написано тут же в комменте #2, правда на английском. В кратце – нужен каверадж в пределах лэйбла и еще остатки вокруг этого лейбла – за его пределами. Я постараюсь в эти выходные сделать статью о том как это собирать – давно уже собираюсь.

С Fusion не работаю, но человек воссоздал в нем мой нюковский сетап по этому делу – думаю добавлю его к статье.

By: Ramon

Ramon — Wed, 31 Mar 2010 12:02:11 +0000

Скажи а если маски по цвету вышли с гребенкой то coverage пасс используется для anti-aliasingа? Как это потом сложить в композе?
со Fusion ты работаешь?

By: Sagroth

Sagroth — Thu, 07 Jan 2010 13:45:20 +0000

Yeap, I’ve found no way to output label as integers to be able to use it in comp (old shaders_p did that as well as I remember – with it’s own openexr writer). Shake supports custom channels from version 4.0, I think, but not tt. Maybe .map file would do – it’s supported by shake and, I suppose, it can store tag data. imf_copy to convert tt into map. You need shake 4.x anyway though to try it.

By: avak

avak — Thu, 07 Jan 2010 00:09:21 +0000

thanks for the response, Actually I am not very good (and I am lazy)in technical issues and I want to find an easy way such as the one that RPF format is doing for max users , as you now this format can save all data such as UV ,depth , object and Render id , coverage and etc. and then combustion can read them in a very easy way .just you need to load the RPF image and apply a 3d filter and mask the specified object based on its id (not rgb) …any chance for Maya and XSI users to have a format like this?
I don’t think exr can save object label information as integer id (am I wrong?)
any plugin for shake that can load tt file not only to load its RGBA data but also to load its integer data that it saves?

thanks for your response

By: Sagroth

Sagroth — Tue, 05 Jan 2010 12:48:50 +0000

I don’t know XSI, sorry. In mi file miLabel attribute adds a line ‘tag #’ in object’s instance block:

instance “pSphere1″ “pSphereShape1″
light “exclusive” []
material ["initialShadingGroup"]
tag 1
caustic on
…

And you need just to output both buffers in camera block:

framebuffer “buff1″
datatype “coverage”
filtering on
filetype “tif”
filename “coverage.tif”

framebuffer “buff2″
datatype “tag”
filtering on
filetype “tif”
filename “label.tif”

Don’t know whether this is useful for XSI though.

By: avak

avak — Tue, 05 Jan 2010 08:30:23 +0000

How it works in combination of XSI and Shake?

By: wiss

wiss — Mon, 21 Dec 2009 09:46:28 +0000

You’re still the man, but … I’m still having problems. Can I send you an example label/coverage set-up to show you?

The issue is that when using this method, some of the edges of the hard mask (after going throug the process) are treated properly and anti-aliased succesfully, whereas other edges remain outside of the reach of the label pass (even after reasonable dilation), thereby being left untreated and “hard” by the process!

Its driving me up the wall! Feel free to send me an email on my address if you’re willing to have a look.

By: wiss

wiss — Sun, 20 Dec 2009 08:24:31 +0000

You are the man!

I actually am doing the same thing as you describe above, but honestly I thought it was a “hack” and not the correct way to handle the passes.

I was only using photoshop to simulate what I ultimately need to do in a Adobe Air application in realtime. I wanted to understand it first, so I could code it properly. Now to figure out how to dilate the coverage by one pixel !

Again, thank you soo much for your original article and for your reply!

wiss

By: Sagroth

Sagroth — Thu, 17 Dec 2009 16:20:15 +0000

Yeah, I want to make a post on how to use these passes for masking in compositing for a pretty long time already… I’ll do it eventually

Anyway, the trick is – label pass shows the object that contributes THE MOST to the particular pixel and coverage pass shows exactly how much. So, in the anti-aliased edges when object’s contribution becomes fainter than 0.5 – label and coverage switches to the object behind. That way it’s obvious that label shows as the object with just a half (>0.5) of it’s anti-aliased fringe and coverage is ranging 1.0-0.5 for this object and then raises up to 1.0 again for the one behind it.

So, what you need to do is:
1) get your hard mask from label pass;
2) get an outline around it (dilate/expand with one pixel should be enough) and multiply this outline by inverted coverage – that way you get those faint anti-aliased pixels you lack;
3) multiply hard mask from label by coverage and add/plus pixels from the step 2 – and you’ve got a pretty similar result compared to standard RGBA masks.

It’s pretty easy to do in any node-based compositing package, though it could be tricky to use in Photoshop.

P.S. If you make this in Nuke, you’d want to gamma up your coverage from the start.