Linear Workflow

[Micha_cg]

Linear Workflow

Gjis was involved in a lot of UI / overall V-Ray for Rhino usage discussion with Corey and Damian. They've brought me up to speed on some of it. We're completely open to his ideas and have already had several meetings about it and other topics (don't worry Micha, Linear Workflow was a big topic )

Fine, I'm curious.

[dalomar_cg]

Linear Workflow

In the coming weeks we will need some feedback as far as the new UI stuff goes. Right now its up in the air as far as how exactly it is going to change, which is why we are going to need some input not only from the advanced users who can say what some of the hangups are, but also the new users who can tell us the problems they are currently running into. I think I will be posting a thread in the coming week

[Micha_cg]

Linear Workflow

Today I was loolink on new video tutorials and the Vray help pages and have seen the sky examples. In the videos I have seen the output of gamma 1.
I ask me - is it right? If Vray light calculation works linear, why not output gamma 2.2? I have the feeling, the examples looks not right gamma corrected. The colors of the heaven are so dark and contrastful. So I have tested to correct the example images (works not perfect with 8bit images).

Whats your thoughts? How works the Physical sky with the LWF? My thesis is, the physical sky is at gamma 1 per default and must be corrected for standard screens.



I'm curious to use this sky in Vray for Rhino.

[Micha_cg]

Linear Workflow

Provocative question ... could it be that the most people at the chaosgroup dosn't use a gamma corrected workflow? In the past I have read, that people are speaking about a typical Vray look. Is the missing gamma correction the reason for it?

If I could post at the chaosgroup forum, I would make a poll "Did you use gamma 1, gamma ~2.2 or sRGB workflow?".

[flipside]

Linear Workflow

Many people don't use the gamma 2.2 correction for their renders. I guess it's maybe 5% of the users that post in the vrayforum that do use it. Then a lot of people read and ask questions about it, but are afraid to actually try it.

Sun and sky works perfectly with gamma 2.2 output. With 1.0 output it looks wrong indeed.

But be carefull because many people use the old 1.0 output and correct the wrong look with some combination of exponential color mapping.

[Micha_cg]

Linear Workflow

... so it's not a VfR problem, it's a general Vray problem. A so little option like a gamma control can bring so much confusion and wrong looking images. Unbelieveable.

[flipside]

Linear Workflow

Yeah but the whole gamma and LWF stuff isn't that old, it's not that we've been using it for years now. Vlado simply did what was possible to put into the 1.5 release, and I really don't think it's that difficult now in max. You simply turn on max's display gamma control, and then you use vray vfb with a)color mapping gamma 2.2 or b)the srgb button. And that's it! The rest of the fuzz is about monitor calibaration, which imo has nothing to do with LWF specifically, but it's simply a general thing to do when you produce any kind of digital image. The problem starts with textures that have gamma 2.2 burned in (almost all textures) and then hdri's that are gamma 1.0 etc, vray cannot decide for you what the gamma of an image is, so you have to specify it yourself. That's where people get confused, will you do it locally on each map, or globally, do you have to set the gamma to 2.2, or 0.455 etc... The essence it pretty simple but it just takes a while to get used to.

[Gijs]

Linear Workflow

Although you are right that Vray cannot decide whether an image is G1.0 or G2.2, I think it is still better that at default Vray makes a few assumptions, and that you can modify to whatever gamma correction you want. Right now it is the other way around: only advanced users know about it and know how to change it.

If Vray for Rhino would make the following assumptions:

-that textures and colors are always offered as G2.2
-that HDRI images are always offered as G1.0

then I am pretty sure that the majority of users will start making better renderings using Vray right out of the box.

Or let me put it this way: right now I always set texture gamma correction for textures to 0.4545 and use gamma corrected colors and leave HDRI images at G1, so I see no risk using that as default values.

[flipside]

Linear Workflow

Yes I agree! It's important to keep the user control over everything, changing defaults is a good idea as long as the user has the ability to change it back if it's necessary. That's why I think the way max handles it is so good, you simply specify your own defaults.

[Gijs]

Linear Workflow

@Micha: I just reloaded the thread that you pointed to about how Maxwell handles colors. So it seems that they scale their colors to make sure the reflectance is not exceeding a certain level?
It would be nice if Vray for Rhino would do something similar. The only disadvantage doing it in a later stage is that you need to redo all your materials...

Corey/Joe will you be considering to tackle this reflecance issue earlier or later?

[joe_b]

Linear Workflow

I suppose it really comes down to how major of a fix is required to correct this issue. If its a major undertaking then it will have to wait - if its just a matter of a little change here or there then I don't see why we couldn't fit it in for our upcoming service release.

[Micha_cg]

Linear Workflow

The current SketchUp plugin give us a preview of the new UI, also the gamma correction.

Joe and Corey, I thought about the current VfSU implentation and think, we must change something more. Input and Output gamma must be independent. It would be good, if the current Rhino gamma control at the color mapping would stay and the VfSU gamma control would control the input colors only. We need both UIs.

Why? Textures are most in gamma 2.2 mode, also the Color chooser works there. Vray works in gamma 1 mode, so we must correct the input colors/textures for the engine. Independent from this, the user should be able to choose the output gamma - for Windows user 2.2, for Mac user 1.8 and for Render freaks gamma 1.

Small bug: the names of the VfSU Reinhard multiplier are not correct now.

[joe_b]

Linear Workflow

Ok - we're still not sure if the gamma correction we're doing now is completely correct in VfS. There is always room for improvement.

[Micha_cg]

Linear Workflow

Hi ASGvis team,

I would like to bring back the idea of the global color/texture multiplier. Please read here. Vlado don't recommend to use the GI multiplier for physical correct usage of the color range 0 ... 255, the usage of a color multiplier is better.

Same topic: the user Lele recommend a color multiplier of 0.25. I have not full read and seen his tutorial, but sounds very interesting. A general multiplier would be a great help. Any chance to get it?

Greetings from the Render laboratory,
Micha

[joe_b]

Linear Workflow

Add it to the wishlist - I'm not sure off-hand if thats something we'd implement right away