[I-0.6] About RGC: the noob's way for an How To

[CTZn]

And, the big secret/scoop is (please wait for the drums to come ): the midtones value in Photoshop Levels IS a gamma value... thanks to suvakas for his support and confirmation about that precise point. So this is an image where I apply RGC for an initial gamma of 2.2 using Levels:



Reverse gamma of 2.2 is 1 divided by 2.2 equals 0.454545 (see Nick's blog)... Here we are... of course because we sometimes try to compensate with tonemapping or energy values or camera white point, it works best by guess. Just lower the midtones knob till it looks better for you.

Conclusion: use midtones not contrast !

And if I'm somehow wrong here, well have no hesitation, my pov is that knowledge grows better when it is shared. If you know precisely there is another/correct way to apply rgc, you are very welcome as well Thx

[playmesumch00ns]

Could this not be done trivially in a shader within indigo? It would save the hassle of having to preconvert your textures all the time.

[CTZn]

That is planned by U3dreal for the 3dsMax exporter I believe, so yes it could be. Gamma-correct me if I'm wrong

[u3dreal]

OK here is a detailed desciption.


This is not only planned this is implemented since the last two versions
I think the blender exporter does this as well ..
actually zuegs brought me the idea to implement this into Max2Indigo..

All you have to do is take the color value in 0 to 1
So something like this <0.4 0.6 0.9>
and use the gamma as the exponent

So you get something like this <0.4^gamma 0.6^gamma 0.9^gamma>

Then the colors are reverse gamma corrected as they will get darker..
And in the end after gamma correction for system (done by indigo)
will be the same value as set in your 3D app.

The Midtone value could be something similar if not the same
but i don't know for sure...you can also use exposure and slide the gamma slider to the left for the value you want to correct to.(2.2)

If you render a pic with rgc textures it makes no sense to gamma correct the plain colors afterwards as the textures they will be corrected by indigo and you will end up with two times revers GC textures..
if you have set texture exponent to 2.2 for render..!!!

So the only way around would be to render all with gamma 1.0
and then reverse gamma correct the picture afterwards...
That's what i did with fillipos pic.

Hope that solved the mistery.

cheer

u3dreal

[CTZn]

I will need some more thought to catch that for sure, but I think that part shows the straighter way:

So the only way around would be to render all with gamma 1.0
and then reverse gamma correct the picture afterwards...

Coz for instance say you have some surfaces untextured, and some with textures with 2.2 as exponent, it becomes impossible to have a coherent image at the end isn't it ?

Anyway thank you for this explanation u3dreal, now I see you did your best

Cheers

[manitwo]

... it becomes impossible to have a coherent image at the end isn't it ?...

no, not impossible - simply use textures even for plain colored surfaces or wait for the next indigo-release.
That's what Ono said: http://www.indigorenderer.com/joomla/fo ... php?p=3147

[CTZn]

Aknowledged, thanks !