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How To Use Exr Buffers Effectively?


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#1 fusionWannabe

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Posted 30 July 2010 - 10:36 AM

From Lightwave, I get these buffers in an EXR:

final Render
Alpha
Raw Color
Reflection Color
Diffuse Color
Specular Color
Refraction Color
Refraction Alpha
Backdrop color
Pre-Effect Color
Special
Luninosity (greyscale)
Diffuse (greyscale)
Specularity (greyscale)
Reflectivity (greyscale)
Transparency (greyscale)
Shading (greyscale)
Shadow
Geometry
Depth
DiffShade
SpecShade
Motion (R,B)

I'm a bit confused about using all the buffers effectively. What really works and is useful in 'normal' day to day work.

I'm trying to figure out a 'general' workflow (if that's possible) to decide which buffers an EXR should contain. I figure it can't speed things up to have more passes than necessary in an EXR, but maybe it's like having an umbrella. Better to have one and not need it, than to need it and not have it.

And - should I create a pass for each light and also for Radiosity?

Do these light passes need to contain different buffers in their EXR files?

When combining the passes, I've seen videos where a boolean is used (as the video said there was no 'add' in fusion). Is that still correct?

And is an add always the correct way to combine each buffer? I'm a bit unclear as some of the video tutorials seem to be using non-linear inputs, and I intend to work in linear. Some used a 'screen' add, which at least according to one fxGuide podcast on linear workflow, is not a good idea to use.

I'd love to see a comp where a pro used different buffers in an intelligent manner.

#2 bfloch

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Posted 30 July 2010 - 11:09 AM

Don't use screen.

There is an add, even two in fusion.
You can set the Alpha Gain to 0.0 with "Normal" apply mode in the merge or use a Boolean Add if you want more control.
There is tons of material about linear workflow in the forums or on the web. Chad is taking breathe to curse you if you ask here :)

#3 fusionWannabe

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Posted 30 July 2010 - 11:27 AM

Don't use screen.

There is an add, even two in fusion.
You can set the Alpha Gain to 0.0 with "Normal" apply mode in the merge or use a Boolean Add if you want more control.
There is tons of material about linear workflow in the forums or on the web. Chad is taking breathe to curse you if you ask here :)


Yes, I figured the tutorials using screen were very out of date. Makes it hard to know which 'experts' I can rely on when I see them using screen to composite non-linear footage. Ahhhh!

I think I've graduated just slightly beyond 'clueless' for a linear workflow. That part is working well.

I'm just after advise on using the linear buffers correctly. I figured the experts would have been down this path and come up with a simplified number of buffers needed to get the job done (unless you're a major studio with unlimited bandwidth and power).

But, maybe that just takes a lot of experimentation - and I certainly don't want to get 'cursed' (hey, I saw what happened in 'Drag Me to Hell')

#4 bfloch

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Posted 30 July 2010 - 02:32 PM

Steve Wright does a good explaination. Look for the Nuke linear Workflow Video or pdf or His great Book.

#5 fusionWannabe

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Posted 30 July 2010 - 03:14 PM

Steve Wright does a good explaination. Look for the Nuke linear Workflow Video or pdf or His great Book.


The 3rd edition has only been out two months.

I just ordered the book for Tue delivery.

You've saved me from getting cursed.

Thanks!

#6 pingking

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Posted 30 July 2010 - 03:59 PM

what passes you need and if you want to break up the seperate ligths depends highly on your needs how much you want to adjust

i think with: RawColor*DiffuseShad + ReflectionColor + Specular Color + RefractionColor you should be able to reproduce the FINAL (at least if i got the exrTrader tutorial right) and in most situation this would give you enough power to adjust the renderings. nice to have is a normal map and a lot of mattes for different materials

what seems strange is the lightwave renders Ligthing, GI, AO and Shadow in to the Diffuse pass (according to the exrTrader tutorial), so i dont know how to split this up

with motion and z depth you can add stuff like motion blur and DOF


seperate lights are only needed if you want to adjust them in post seperatly, e.g. if you want to make one flicker or change color or something

#7 fusionWannabe

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Posted 30 July 2010 - 05:09 PM

what seems strange is the lightwave renders Ligthing, GI, AO and Shadow in to the Diffuse pass (according to the exrTrader tutorial), so i dont know how to split this up

Do you have issue #30 of hdri3d
http://www.hdri3d.co...=163&Itemid=100

The Gerardo Estrada article "Nah! You canít do that with LightWave!" gets into how to get almost any buffer out of Lightwave using the DPont Extra Buffers nodes (and a few others).

I ?think? that the next version of exrTrader is going to support the Extra Buffer nodes.

But - in the article, Gerardo said that everything he's doing with the extra Buffer nodes could be duplicated in a compositing application (or, I may be misreading what he's intending to say).

Anyway, it's an interesting and very long read (must be 20 pages).

BTW - to setup exrTrader presets for Fusion, what did you have to do?

I believe it is:

'un-multiply by alpha' un-checked
'fit data window' checked
set to 16 bit float HALF (unless you require 32 bit float)

But, there's maybe one other change? Mike Wolf was busy at Siggraph, but said:

"I think the only thing that needs to be changed is the name of the motion buffers to VelX and VelY (no layer name)"

Is that about it?

Thanks!

BTW - just got this post were Janus http://janus.faulknermano.com/ (which works well with exrTrader and really automates a Lightwave multi-pass workflow ) does support these extra buffers I just mentioned in the newest (un-released) version.

http://www.newtek.co...109#post1043109

#8 robocop

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Posted 30 July 2010 - 06:57 PM

i highly! recommend this tutor :
http://www.thegnomon...re/product/431/

the best what i saw about multipass compositing.
really.

#9 fusionWannabe

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Posted 30 July 2010 - 10:08 PM

what seems strange is the lightwave renders Ligthing, GI, AO and Shadow in to the Diffuse pass (according to the exrTrader tutorial), so i dont know how to split this up


Doing a bit of research on Newtek forum, and found this:
---
http://www.newtek.co...98&postcount=36
If you have a Shaded Diffuse pass (lw's buffer saver which has light color and diffuse texture color) and a raw RGB pass, divide them by each other and you've got a diffuse lightng pass!
---
I'll see if I can come up with some rules to generate different passes that seem to be missing from the existing ones.

Between Gerardo's article, the new versions of Janus and exrTrader (that will hopefully be out soon), I think this is all very doable!

BTW - here's a very interesting thread on render management covering three years, started by Gerardo:
http://www.spinquad....nder-Management

He really seems to know how to make Lightwave do just about anything.

#10 fusionWannabe

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Posted 02 August 2010 - 10:10 AM

i highly! recommend this tutor :
http://www.thegnomon...re/product/431/

the best what i saw about multipass compositing.
really.

Thanks, I'm watching this now.

I suppose the same techniques apply for the passes no matter what the format, as he's using tga files so far.

#11 ChadCapeland

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Posted 02 August 2010 - 10:19 AM

Only render out the extra buffers you intend to you immediately. There's no point in having all that extra I/O load for something you won't use. Better to just learn better techniques for render pass generation, rather than consumption.

#12 fusionWannabe

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Posted 02 August 2010 - 10:54 AM

Only render out the extra buffers you intend to you immediately. There's no point in having all that extra I/O load for something you won't use. Better to just learn better techniques for render pass generation, rather than consumption.

Good advise indeed.

Hopefully with this video tutorial and the book that comes in tomorrow, I'll get a handle on how which render passes I need and how to set them up properly.

At the moment, I'm rendering all the passes, so that I can experiment a bit.

Thanks!

#13 fusionWannabe

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Posted 03 August 2010 - 05:00 PM

i highly! recommend this tutor :
http://www.thegnomon...re/product/431/

the best what i saw about multipass compositing.
really.

He's saying that a color corrector should NOT be used for floats, that the colors get inverted for anything over 1.0, and suggests using a color gain tool instead.

I'm going to have to go over his examples, convert his tests with gradients and such to linear, and see what happens?

I certainly don't know what I'm doing, but I think he's making some very basic errors while working on his 2.2 gamma images using Fusion (which I believe does its magic internally as linear)?

#14 Eagle1

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Posted 03 August 2010 - 05:12 PM

Fusion Multi-pass compositing
http://vfxhaiku.com/...ass-compositing

Lightwave Render Buffers
http://janus.faulkne...derBuffers.html

:rolleyes:

#15 robocop

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Posted 04 August 2010 - 12:25 AM

He's saying that a color corrector should NOT be used for floats, that the colors get inverted for anything over 1.0, and suggests using a color gain tool instead.


Yes, hi is speaking about TintWheel of CC tool. and its right.
is not gamma issues. is tool behaviour.

i prefer gain and colorCurves tools rather then CC.
look the comp- "why".
Attached File  CCvsCgain.comp   8.91KB   11 downloads

and offcourse - i use CC too! but with understanding of what i`m doing.




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