How to get better VRay renders (aka working in linear space)

[rpc212]

well, your software should apply the 2.2 at some point.
I know that in nuke, if i write out a .jpg or .png or .rgb it bakes the 2.2 into the image so that i know i have a gamma corrected 8 bit image.

Ok, I think I am confused. So when I take the image out of the compositing software, saved as a tiff or whatever, I have no colour profile attached to the image so this is why photoshop asks to attach a colour profile or not. Should I answer yes and attach a sRGB colour profile?

Thanks,

rpc212

[rpc212]

Hi,

Uhh, is this question not answerable? Surely one wants a colour profile attached to an image, or so I have read in Photoshop Colour Correction by Michael Kieran.

rpc212

[Metin_7]

Great tutorial! Couldn't live without the new gamma-corrected smoothness of light and color anymore.

A tip from my side in return:

After you've forced the gamma and bitmap gamma to 2.2 in your Max preferences and you need to have an exact RGB color value in your render, just add a ColorCorrect map (very useful free plug-in from http://www.cuneytozdas.com), activate the gamma and set it to 2.2 to neutralize the gamma correction for a color or map.

Cheers!

Metin

[davision]

Just a note --- I thought Vlado stated that ColorCorrect had issues with Vray and could cause spots or blotches.

I personlly haven't seen many issues with CC, but I think they can arise in certain circumstances.

[Metin_7]

Hi,

You might be right, but I hope CC will only cause problems when using certain options, maybe causing overbright highlights or so.

Cheers,

Metin

[sv]

I have watched this post for a while now, and think that a lot of the techniques described will doubtlessly help improve accuracy of lighting and render times. However, i have been playing around with it, and just can't work out how you get the final adjusted image to look how i want it too look.

A lot of the time my renders seem so dark and there is so much contrast between them, so that is why i want to use this technique.

I have adjusted my gamma in max, rendered out to .rpf, loaded the file into combustion, used a LUT view, saved the image as TIF, and when i open it in photoshop, it's all dark again.

I kind of understand that you don't burn the curve into the image through vray, and it is a post production thing, but it doesn't seem to be working. My major worry is that i will create and image, adjust the colour settings and gamma etc in post so it looks fine on my screen, then send it off to a client who will complain that it is too dark because there is such a difference between a LUT adjusted view and a "normal" monitor. Like someone said - 99% of people don't need to know about sRGB colour spaces, but they will be the people looking at our final renders.

So how do you adjust the vray output so that the image itself is adjusted, rather than your working colour space?

[Gijs]

SV,

I have been using the technique described here for quite some time now and must say I have gotten better control over my output than before, where I was always fiddling with colormapping.

To get the output right away (thus the curve burnt into your image) use the gamma correct color mapping, set bright color map tp 1/2.2 (about 0.45454) and render to Vray Framebuffer. Your RGB color channel will be the corrected image, your RealRGB channel (if selected in GBuffer output channels) will remain unaffected.

So Gamma correct colormapping is basically the same as linear, with the difference that it can bake the gamma correction into the RGB channel.

[rpc212]

Hey Gijs I did what you said and adjusted the gamma correct color mapping to 1/2.2 (about 0.45454) and rendered in Vray Framebuffer. It looks really good. Do you keep "Enable Gamma Correction" checked under "Preferences"?

Now my question is for Gijs or Throb or anyone else who can answer this.

I went and unchecked "Enable Gamma Correction" on the "Gamma tab" in "Preferences" and now when I duplicate the Vray FB to Max FB I get an exact copy. Whereas, if I leave the "Enable Gamma Correction" checked the Vray FB duplicate to Max FB is blown out and pretty much useless for comparing one render to the next. I know this is going against Throb's tutorial however the results look the same with the gamma correct color mapping adjusted to 0.45454 as checking the "Enable Gamma Correction" with the big difference being that duplicate to Max FB now works making the workflow, in my opinion, way better.

So, by turning the gamma correction off am I now not working in Linear space even though I have made Gijs's adjustment?

Thanks,

[Gijs]

Yes I keep Enable gamma correction checked.

Enable gamma correction is only a display thing. So what you are doing (turning off gamma correction to be able to duplicate to the max frame buffer) is no problem. However, it is advised to turn it on, to get more realistic material previews.

At first, when this thread was started, there was no gamma correction color mapping. Vray framebuffer remains unaffected by max gamma correction. That's why Rob described to use a correction curve in the Vray frame buffer to view the image in linear space.

To keep things clear: there is no problem to save a corrected image (read the Vray Frame buffer rgb channel) when you are not using it for film. But since Rob works in the film industry, he will use the uncorrected version (the real rgb channel) in the rest of his pipeline.

But even if you don't work in film industry, rendering this way gives more natural light fall-off and light distribution.

I hope this clarifies things a bit.

[rpc212]

So if there was a duplicate to Vray FB that would solve the problem of the blown out duplicate to Max FB?

How do you work to compare FBs Gijs and analyze problems between renders?

[sv]

thanks for the clarification. I also agree that this technique produces much more natural looking light dispersion.

[rpc212]

Ok there is a way, with the gamma correction colour mapping that Gijs talked about, to duplicate the Vray FB to Max FB and have the same lookig result and thus still be looking at/working in Linear Space.

Simply turn the "use colour curves correction" button off when you want to duplicate the Vray FB to Max FB and you will get the same image because the colour correction curve has been burnt into the image through colour mapping. Then before your next render turn the "use colour curves correction" button back on.

Is this workflow correct or am I correcting the image twice before viewing it?

thanks,

[Gijs]

Hmm, if you are using gamma correction color mapping in combination with the correction curve Rob descibed, you are correction twice. I for one, wouldn't use the curve anymore, rather use gamma correct colour mapping.

I don't compare renderings in max, just save all subsequent steps to a png file and use an image browser to compare. Works better for me, otherwise max gets too cluttered.

[rpc212]

Aha. Thanks Gijs! Now I understand.

[dbuchhofer]

Btw, the link in the first post is dead and needs updating if anyone has a working one handy..

cheers