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View Full Version : Re-assembling exr channels for beauty render



ernpchan
03-30-2015, 12:57 PM
I'm finally getting into Nuke and dealing with exrs.

Does anybody have a link documenting what blend modes each pass needs to be set to to make the original beauty pass?

mummyman
03-30-2015, 02:08 PM
Here's an excellent link: https://www.youtube.com/watch?v=m4sVez6aC5E

And there's also this older link: http://www.lightwiki.com/wiki/Multipass_Rendering_with_Filter_Node_Editors

ernpchan
03-30-2015, 02:15 PM
Thanks!

mummyman
03-30-2015, 02:21 PM
Good luck! Hope it helps

Axis3d
03-30-2015, 02:39 PM
I dont have a link to anything but here are a few tips I've experienced using Nuke and Lightwave:

I have found that EXRTrader works better for saving out passes than Lightwave's Compositing Buffer Export. Lightwave's Diffuse pass seems to combine the shadow pass in it, and EXRTrader keeps the Diffuse clean, without the shadows (this is preferred for compositing). I've also noticed a graininess to the passes, in general, with the Compositing Buffer Export that I didn't notice in EXRTrader.

Depending on what you are rendering out, I usually render these basic passes, then add more if I need them:

RAW
Diffuse
Shadow
Spec
Reflection


The Diffuse and Shadow get Multiplied over the RAW. The Spec and Reflection use the Plus transfer mode.

Also, you will want to change the Color Space Tab settings in Lightwave to use the sRGB quick preset. And be sure to change the Output Color Space to Linear. This will ensure a clean Linear workflow in Nuke.


I also have been using Lightwave's Compositing Buffer Export (rendering out multi-layered EXR's) with an After Effects Linear workflow.

ernpchan
03-30-2015, 03:12 PM
Thanks, very helpful information.

gerardstrada
03-30-2015, 08:07 PM
You might find this formula useful too:

http://forums.newtek.com/showthread.php?132920-Compositing-and-passes-workflow-from-LW!!!-WTF!&p=1293826&viewfull=1#post1293826

Btw, when saving LW exr files (LW 11 and above), there's no need to switch the output colorspace to linear anymore. LW will save them as linear automatically no matter what the output colorspace is. Setting up the output colorspace according to the actual output medium is advisable when using Adaptive Sampling, seeing that LW will use the output space in the CS panel for calculating the contrast threshold.



Gerardo

ernpchan
03-30-2015, 09:00 PM
Thanks!

Axis3d
03-31-2015, 07:30 AM
You might find this formula useful too:

http://forums.newtek.com/showthread.php?132920-Compositing-and-passes-workflow-from-LW!!!-WTF!&p=1293826&viewfull=1#post1293826

Btw, when saving LW exr files (LW 11 and above), there's no need to switch the output colorspace to linear anymore. LW will save them as linear automatically no matter what the output colorspace is. Setting up the output colorspace according to the actual output medium is advisable when using Adaptive Sampling, seeing that LW will use the output space in the CS panel for calculating the contrast threshold.



Gerardo

Yes, you are correct about the colorspace. Good to know. I did a test render with saving exr files (one with output colorspace set to Linear, one set to sRGB). The one set to Linear looks much granier than the render set to sRGB. The Adaptive Sampling was the same on both of them.

Is this what you meant by "Setting up the output colorspace according to the actual output medium is advisable when using Adaptive Sampling, seeing that LW will use the output space in the CS panel for calculating the contrast threshold."

gerardstrada
04-02-2015, 06:25 PM
Yes, that's it!

Having the contrast threshold applied according to the output medium maximizes AA sampling efficiency in the correct tones of the image.

My original images are missed here, but there's more info about this topic in this thread:

http://forums.newtek.com/showthread.php?119485-Why-is-the-quot-Adaptive-Sampling-quot-pass-so-slow&p=1144504&viewfull=1#post1144504



Gerardo