"Custom mapping" via vfb curves

[Karonte]

Hi guys,
i was trying to get my head around color mapping and i got an idea:
Can i work with gamma correction and LINEAR color mapping, and then apply a personal, custom mapping using the vfb curves?

I made some tests with a pretty standard setup (2,2 correction in vray, linear 1/1) and it seems to work. In the examples i took the raw, linear output and applied an “exponential - like” curve to it inside vfb. The result was very similar to the one with native exponential mapping, but I got a huge improvement in both flexibilty and interactivity.

So: is this correct? So i'm no more bonded to choose color mapping "before" render but "choose it" in realtime. This seems to me a truly interesting workflow. It should be similar to exporting a linear openexr and working with exposure in other softwares, right? we could have some preset curves in the vfb( exponential, reinhard, ec....) to start from.

Now, time for technical doubts. What are the possible disadvantages of this kind of workflow? Applying a later curve on an already cooked buffer can lead to errors or lack of "precision"? Should i worry about artifacts, noise or with the sampling struggling to remain acceptable after the correction?

What should the most solid and less convoluted setup be? Maybe working in full linear (no gamma correction) and using the srgb option? gamma corrected, with don't affect colors?

Chaos, a personal question: the vray team implemented the curves system for an use like this? do you have plans to make the curves directly avalaible in the activeshade too, and maybe to make it less clunky? please vlado, tell me so

[samuel_bubat]

Well, basically it doesn´t matter how you achive a look. What counts is the result and nothing else.
So if you feel comfortably this way, go for it.
If you plan to raise pretty dark areas later (wich way ever) you may need to decrease the adaptive amount
of the DMC sampler or blotches may occur. But you´ll have to test it.

I for my part don´t use any linear workflow at all.. no gamma correction, no physical camera exposure, no physical sun.
Just strong standard lights (a sun is nothing else than a strong direct light) and a strong environment. I do exposure just by
Reinhard color Mapping. Like this I can get even a room with the smallest windows bright without harming any muliplier, using
Skylight Portals or using any other dummy lights.

It´s just my personal opinion and everyone should use the workflow he likes.
But all this "physically correct" stuff as well as linear workflow is utter nonsense !
First you bind yourself to realworld obstacles like a very limited range of a physical camera. Than you
are not physical at all because you don´t have physical correct materials unless you make a BRDF measurement
of each and every material.

cheers

[wxyz]

+1 for a more controllable system. As light changes during an animation it would be nice to animate the settings of the curve.

[vlado]

Like Samuel mentioned, just use whatever works. As he noted, the only problem that might arise is if you try to lighten up dark areas too much in which case you'll have to play with the sampling a bit to make sure V-Ray puts more samples there.

Best regards,
Vlado