Chaos Corona Forum
Chaos Corona for 3ds Max => [Max] I need help! => Topic started by: hrvojezg00 on 2018-03-30, 09:50:40
-
What is the best way to work with photography as backplates directly in 3dsmax/Corona? Problem I have is that we usage LUT`s for all production, but that also applies LUT to the background photograph that is in the scene which has been previously color graded/adjusted by the photographer. Is there a way to de-LUT photographs or something like that to have both modeled scene and the photo at the same contrast/color? I would like to avoid adding it in PS in postproduction to maintain native Corona glare/bloom.
Thanks!
-
+1
-
I’m also interested in this.
-
Many interested, anyone know the solution?
-
At the latest daily there is the CoronaToneMap map that enables to override LUT,exposure, tone-mapping in CFB.
-
That sounds like the solution. We try to stay away from daily builds, any info when new version with it will be released?
-
In older versions (anything before Corona Renderer 2 daily builds), the CoronaOutput map can do that - the daily builds just split CoronaOutput into 2 maps since there are 2 different uses that are never used at the same time. So, passing your background photo through a CoronaOutput and using the "Affected by Corona VFB tone mapping" checkboxes should get you the result you need.
-
Just keep in mind that in most cases neither CoronaTonemapControl, nor CoronaOutput cannot faithfully undo LUT applied to images. I guess that best approach would be replace background in photoshop.
-
Good point - both the old and new Corona maps are simply for avoiding applying the LUT and tone mapping in Corona's post to the background image. They do not "un-LUT" the image in any way, but simply avoid applying Corona's changes to it. This should mean, though, that you can apply the same LUT to the render, and leave the background as-is (with the LUT already applied) and all should be well... if I understand what you are doing correctly :) This would make "remove the LUT and then re-apply it in Corona" redundant. But, I could be misunderstanding what you are aiming to do.
-
Tom, that's only how that node behaves in theory.
In practice, it works on everything except for the LUT. It always had this issue.
So currently the only solution in this situation is to not apply LUT in this particular case and wait for Photoshop/other compositor.
Yes in theory you could apply inverse correction to the Background but that wouldn't work even if that background was linear 32bit files. LUT is destructive.
-
Ah yes, the non-monotonic operator warning, forgot all about that. In which case, the new CoronaToneMap node works the same way too so there is the same issue. Only thing I can think of then is to replace the background in post using alpha - could then either use a separate Bloom and Glare pass to use the native Corona bloom and glare (but only from objects in the scene), or use the CIE to apply the bloom and glare after compositing the background in (if wanting to have B&G work from elements in the background image too).
-
I am actually confused about that part with B&G issue. How does not being able to use LUT in framebuffer destroy the option to render B&G directly onto beauty pass ?
LUT doesn't affect B&G in any way. Only that B&G is computed on top as last step but that won't make big difference, and shouldn't be the correct order anyway.
-
Ah yes, the non-monotonic operator warning, forgot all about that. In which case, the new CoronaToneMap node works the same way too so there is the same issue. Only thing I can think of then is to replace the background in post using alpha - could then either use a separate Bloom and Glare pass to use the native Corona bloom and glare (but only from objects in the scene), or use the CIE to apply the bloom and glare after compositing the background in (if wanting to have B&G work from elements in the background image too).
But how to work out background replacement that is visible in reflections (mirror) in post?
-
That one would unfortunately come down to "don't apply the LUT to the background image at all, and do all the color correction after rendering" as the best solution, or using object masks and compositing raw render without LUT applied in Corona and render with LUT applied (though would only work with 100% reflective things like mirrors, if there was diffuse etc. in there it wouldn't work as the object would need the LUT applied - hopefully though in those cases the reflections would be dim enough that the fact they were "double LUTted" wouldn't be obvious.) At least, those are the only solutions I can think of, someone else may have other ideas!