display gamma in RT

[jujubee]

Again for the thousandth time - there are two different ways to go about linear workflow. One is to "burn it in" and the other method involves using the "sRGB" button. They involve slightly different settings.

"Burning in" LWF is much easier - but unfortunately doesn't work with VrayRT at present. So you are stuck using the "older", original method of using the sRGB button in order to achieve more accurate results with VrayRT for now.

And for those that are setting Max Preference gamma Material Input to 2.2 - that is completely wrong. It should be left at 1.0 unless you converted ALL of your bitmaps, texture libraries, and photos in Photoshop to 2.2 gamma space - which is highly unlikely. Stop spreading misinformation please.

[bluescreen2]

my workaround is setting vray gamma back to 1 when using RT. anoying if you forget setting back to 2.2 for the final and you are realising this after an hour of rendering ^^

[devin]

I'm pretty sure I've tried both of these and although the RT image is much closer to the VFB it's not an exact match. I'd like to see some examples of these methods so I can see what kind of results you are getting.

[Shimakaze]

Again for the thousandth time

I should really get around to writing that comprehensive LWF guide one of these days...

[rmejia]

I should really get around to writing that comprehensive LWF guide one of these days...

There's a good gamma correction pdf tutorial in this website, which might be helpful:
http://scripts.breidt.net/tutorials.html#gamma
"Be gamma correct: Long article on practical gamma correction"

[Pixelab]

And for those that are setting Max Preference gamma Material Input to 2.2 - that is completely wrong. It should be left at 1.0 unless you converted ALL of your bitmaps, texture libraries, and photos in Photoshop to 2.2 gamma space - which is highly unlikely. Stop spreading misinformation please.

Are you sure about that ? Ok for bumps and displace, for which you can still override, but diffuse maps still need to be corrected.... Am I wrong ?

[jujubee]

Don't set the bitmaps (textures)/Material Input you are reading to 2.2. That is wrong. 98% of all your textures were created in a proper gamma color space for LWF.

It's 3dsmax itself which is screwed up (using a difference space by default) compared to the rest of the VFX/Graphics world - that's the whole point to LWF.

[Shimakaze]

98% of all your textures were created in a proper gamma color space for LWF.

Well that highly depends on where you get your textures. Most textures you download for free online for instance are in sRGB space and has to be corrected, as are many commercial packages. Also if you've made your own from photos then chances are you didn't think to make them linear at the time since pretty much all digital cameras operate in sRGB or Adobe RGB spaces.
On a normal computer screen, if a texture looks good in a web browser (and most picture viewers) then it is most likely not linear. If it is it should look dark and saturated.

Basically you need to evaluate this on a per texture basis. Either set the gamma when you load textures, or manually convert all your textures to linear space before hand (not recommended if you use a lossy format like jpeg).

[stevesideas]

Well that highly depends on where you get your textures. Most textures you download for free online for instance are in sRGB space and has to be corrected, as are many commercial packages. Also if you've made your own from photos then chances are you didn't think to make them linear at the time since pretty much all digital cameras operate in sRGB or Adobe RGB spaces.
On a normal computer screen, if a texture looks good in a web browser (and most picture viewers) then it is most likely not linear. If it is it should look dark and saturated.

Basically you need to evaluate this on a per texture basis. Either set the gamma when you load textures, or manually convert all your textures to linear space before hand (not recommended if you use a lossy format like jpeg).

Every texture Ive ever come across (those found on cgtextures.com for instance), are in a SRGB format (as far as I understand). So, if im using LWF I make sure that the gamma setting in the load dialogue is set to 2.2 gamma. Is this correct ? Then, the texture looks exactly the same as the preview on cgtextures....basically, like a standard photo. It doesnt look over-staturated or dark.

[theedge]

Well, I'm not a GG (Gamma Guru) but the way it seems to work and make sense to me is :

When you activate gamma correction in max preferences and set it to a value Gm that becomes the reference, the target gamma. Max will then bring all incoming images to that "standard"

Thanks to the input gamma value Gi that we specify, max will know what correction C to apply to the images : C = Gm/Gi

So :
- if Gi = 1 then max will apply a C=2.2 gamma correction to the loaded bitmaps
- if Gi = 2.2 then max will apply a C=1 gamma correction and won't change the images.


Now if -as it is usually the case- our images are already at 2.2 and we specify a Gi of 1, they will get double corrected and end up washed out. So it's preferable to set a Gi of 2.2 in most situations.

That's also what I understood when reading 3ds max help about the gamma/lut pane.

So is my understanding right or no ?

[flipside]

I also use gamma 2.2 correction in the gamma/lut preferences (+affect material editor and color selectors). Then I also set gamma to 2.2 in the vray color mapping rollout to burn in the gamma.

With this setup, you have to specify the gamma of your textures correctly. And 99% of all textures should be specified in max as gamma 2.2. It's easy to check, the texture in your material editor should look exaclty the same as the texture viewed in an image viewer. If not, you did it wrong. Since 99% of all textures should be set to gamma 2.2, people tend to set input gamma to 2.2 so they don't have to manually specify this each time they load a texture. Nothing wrong with that Juju.


Attached is an image showing the two setups, and the texture viewed in material editor, clearly looking correct. When you render an object with this texture, it will also look the same as here, not washed out, not dark and saturated. (with the setup as described above).

When you leave input gamma to 1.0, and you don't specify the gamma of your textures in the bitmap loader to 2.2, your textures will look wrong!

[flipside]

But what I wanted to ask, from the changelog of RT sp1:

- 0001826: [feature request] Some gamma workflows did not work well with the ActiveShade;

What has changed, because I can't find anything different.

[vlado]

But what I wanted to ask, from the changelog of RT sp1:

- 0001826: [feature request] Some gamma workflows did not work well with the ActiveShade;

What has changed, because I can't find anything different.

There was an issue for example, when the user has chosen 2.2 display gamma in the 3ds Max preferences, but is using the V-Ray VFB to render with 2.2 gamma in the "Color mapping" section of V-Ray. In that case, the ActiveShade view ended up being gamma-corrected twice, which is now fixed.

Another scenario was using the sRGB button in the V-Ray VFB; V-Ray RT now checks this and applies the respective correction to the ActiveShade view as well.

Best regards,
Vlado

[flipside]

Ok sorry vlado, I use the first scenario yoiu describe, and tested it a few hours ago, but for some reason I didn't see that it was fixed, so went looking for some kind of button and didn't see anything new.

So no problem, all is fine now

thanks!

[flipside]

Mmmm, not quite. It's only working when I set input gamma to 2.2, even without using any textures in the scene. I specify the gamma of each texture manually when loading it, so I always leave input and output gamma to 1.0.

Does the input gamma have an effect on the activeshade window too?

Thanks