Thanks Michael!
I think I got reasonably close with my expression hackiness yesterday
and with a little help from somebody else we got even closer (basically
by doing the soft part of the mask in flat image space).
Hopefully we are good to go now.
On 18/06/14 3:25 am, Michael Garrett wrote:
If all the samples are at the "same depth" in both A and B, easy, the
output samples are a simple mix between each sample of A and B.
This is
the case for, say, keymixing in a DeepColorCorrect (where only the
existing sample values will be changed)
I managed to get a deep volumetric keymix working using the basic
scenario Ben is describing with deep holdouts - one with the mask and
the other with the inverse mask, then deep merging them together.
Typically I used this when creating a deep Pmatte then using that as a
deep keymix for a deep colorcorrect/grade.
And yes it was extremely useful. I'll have to revisit the specifics
though because like Ben says I think there was some additional work
required to get rid of fringing issues which since I have yet to write
a plug-in, was achieved with deep expressions (hello hackiness).
This was specific to Mantra. I have yet to extensively use the deep
output from other renderers but I believe Mantra's deep output has
it's quirks and what I did may not translate exactly to another
renderer. Also we were working a fair bit with full deep rgb output
which can make things a lot cleaner, although we did fall back to deep
opacity/recolor in some cases as deadlines approached and still got an
acceptable result.
Cheers,
Michael
On 17 June 2014 02:09, Ben Dickson <ben.dick...@rsp.com.au
<mailto:ben.dick...@rsp.com.au>> wrote:
It's more difficult than it initially seems..
The obvious thing is to use the DeepMerge set to holdout to punch
a hole
in your A input, invert the matte and punch the inverse hole in the B
input.. but when you merge these you get the dark fringing where your
matte is semi-transparent, which is the same problem solved by adding
the two images together, or using the disjoint-over
..but, you inherently cannot do that with deep samples - when the deep
image is flattened, all the samples for a pixel are over'd.
There is a DeepKeyMix gizmo on Nukepedia, but it is very destructive -
it flattens the image with DeepToImage, applies a regular KeyMix and
then uses the DeepRecolour.. which is probably okay if you are only
rendering deep-opacity, but bad if you are rendering deep-RGB.
I had a rough idea of how to write a plugin to mix between two deep
images, but haven't got around to implementing it.. so.. there
might be
some other fundamental flaw in the approach, but..
For two inputs "A" and "B":
If all the samples are at the "same depth" in both A and B, easy, the
output samples are a simple mix between each sample of A and B.
This is
the case for, say, keymixing in a DeepColorCorrect (where only the
existing sample values will be changed)
If the samples are not aligned, things are more complicated (e.g
mixing
two separate renders). For each sample you need to make a
corresponding
sample at the same depth in the other image, by interpolating between
the nearest two samples.
In other words, if you have two images like this:
A samples: empty empty red empty black
B samples: empty empty blue blue blue
1) For first two empty samples, nothing is done
2) For the A:red and B:blue sample pair, output sample is a simple mix
3) For the A:empty and B:blue sample pair,
insert a sample in A which is a mix between the "red" and "black"
samples. Then mix between that and B's blue sample
I think the case which would cause artefacts is when your samples have
large distance-gaps between them: like keymixing between a foreground
tree and the sky - the process of creating the new samples will create
"tree" coloured samples at the "sky" depth and vice-versa
- Ben
On 17/06/14 12:40, Frank Rueter|OHUfx wrote:
> Hi peeps,
>
> I'm just trying to figure out how to merge two deep images based
on a
> deep mask channel, without getting fringing.
> Been playing with DeepExpression but don't know if I can reference
> samples in there (the documentation is rather sparse to say the
least).
> Basically I need a true, volumetric DeepKeyMix.
>
> Any ideas?
>
> Cheers,
> frank
>
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