Linear Workflow
As for changing the gamma of your bumpmap: I think it makes sense to change the gamma for a gray scale image, because it influences the midtones. you can question however if you’re going to see the difference…
Linear Workflow
It’s on my personal wishlist since a few weeks and I will buy it soon. 
I would buy a ColorVision Spyder. Can you recommend a device?
Some posts befor you can see an example with primary 0.8 - the LC pass dosn’t match with the final rendering. The LC pass is darker. But I like to use the LC pass for fast preview and adjusting the lighting of a scene. The truth is, we are fumbling with this partial solutions. :?
What we need is a general color and texture multiplier 0.8 for physical correct workflow!!! For example Maxwell user know the physical rule (it is like mandra for beginners), but can not set partial multiplier (this is good so) and must set all colors and textures manual at 80% (except bump and reflection maps). I think, we could make is easier.
We can not set colors/textures at 80% for GI only. This is not correct. We would get a wrong ratio between GI light and direct light and object color/ object reflection. If a white color should be a 80% grey, than it must be a 80% grey for anything. So, the way of the maxwell user is physical correct. OK, I could set my textures at 0.8 and could correct any colors per Acolor multiplier 0.8. But a general multiplier could make the workflow easier. Also, the manual correction dosn’t work for Rhino materials. :?
I would like, if we could make, that Vray can be used from everybody in a physical correct way. I would like, if we could set global options:
* gamma output - 2.2
* texture and color gamma - 0.45
* color and texture correction - 0.8
So, every new user could use the standard colors and textures and anything will be good. He must not think about gamma options and 80%.
Gijs, I would be happy, if we could discuss this topic until this 80% problem is solved. It’s so important.
Linear Workflow
OK, now in order to get things together we must at least agree about what is physically correct and what is not.
1 Do you agree that for physical correctness, both primary and secondary multipliers should be left 1? (and rather correct things at material level)
2 What you are saying about the 80% for colors and textures is related to diffuse color only right? (as opposed to using it for everything including fog color, reflection color, filter colors, etc)
if both 1 and 2 are a yes, then I suggest that it is better to make a prominent note in the help files or a tooltip that guides you. Anyhow we should make a recipy for making physically accurate renderings and still leave it up to the users if they want to make use of it and where they want to step away from these rules to achieve a special effect.
As for correcting textures, how could you tell me that a certain texture doesn’t already has the right HSV values? I think it is ‘dangerous’ to correct textures automatically by multiplying them with 0.8.
As for the spyder: I don’t have experience with those, I have used i1color and they work good. You should however google around for the best choice, because I once read a test that had different recommendations depending on the brand and type of monitor.
Linear Workflow
1 Do you agree that for physical correctness, both primary and secondary multipliers should be left 1? (and rather correct things at material level)
Yes, this would be good.
2 What you are saying about the 80% for colors and textures is related to diffuse color only right? (as opposed to using it for everything including fog color, reflection color, filter colors, etc)
Right.
As for correcting textures, how could you tell me that a certain texture doesn’t already has the right HSV values? I think it is ‘dangerous’ to correct textures automatically by multiplying them with 0.8.
I never have seen physical correct textures. Most commercial texture bundles are simple textures with white = 255. Everywhere I see color values around 255. I suppose so, the most user use textures like this. The global diffuse color multiplier is most important for Rhino object based materials.
Do you agree, a diffuse color multiplier make sense? The user could choose to let it at default 1 or at 0.8.
Linear Workflow
Maybe there could be added an automatic Rhino to Vray material converter to solve the Rhino material issue. Or let mcneel add a multiplier button
Because there is already the option in the bitmap loader to change the multiplier. I still don’t think that a global texture multiplier makes sense. In fact when you use a texure, you should actually be able to look up the reflectance value of that particular material and base the multiplier on that. So suppose you have a wood texture with an average reflectance of 50% and the average of the bitmap is like 70%, then the multiplier would be 0.71. I don’t think that all textures have the same ‘error’ as they are all photographed or scanned often with autocalibration.
btw, just a few post back I mentioned this:
And also it (maxwell) will have a texture correction internally without doubt.
here is the proof (look for Tom’s answer)
http://www.maxwellrender.com/forum/viewtopic.php?t=17275
Linear Workflow
I have the feeling, that textures are allways captured to bright, but very seldom to dark. So, a global correction of 0.8 could be the right direction. We don’t know, how much correction we need, this is true, but 0.8 could be a good approximation. The error between 0.71 and 0.8 is not so high as between 1 and 0.8. I have the feeling, don’t touch the value and let it at 1 allways produce a higher error than a default usage of 0.8.
An other example: color system like NCS or RAL are working in non physical correct mode too. For example RAL 9016 Verkehrsweiss give me a intensity of 96%. :shock:
If we can use options like global GI multiplier, than we should get an option like a global general diffuse color multiplier too. I don’t understand, why the one option makes more sense, but not the other.
I think, the problem is, that classical raytracer used 100% white colors and it was right so. If somebody has used the 100% color system, than classical texures are right too. But we have a new situation, the new engines like Maxwell and Vray need to be physical correct below 80%. I think, a global correction could help to go in this direction and could help to avoid to much work on texture/color settings and would help we can better use the Rhino materials.
So, the only disadvantage seems to be, that a coorection of 0.8 would not be the right factor for any case. But most we don’t know, which correction is the right, - we only know, we need a correction.
PS: I’m curious, how maxwell will handle this problem.
Linear Workflow
Gijs, do have seen this here. It seems to be Maxwell do an internal correction, but for my taste to much.
Linear Workflow
Yeah, I’ve seen that one. I think your assumption is right (about the internal correction). The main difference between Maxwell and Vray (apart from the rendering speed of course) is that in Maxwell there are certainly made a lot of decissions behind the scene. That is what makes Maxwell produce quite high quality right out of the box.
I think that they have been brainstorming about what can go wrong if someone just starts using the software. One of them has probably been the ‘too high reflectance problem’. My hard guess is that colors are not clipped, but that they put a curve on the colors that is let’s say linear up to 70% reflectance and then goes asymptotically to something like 85% reflectance.
What I would probably find better is if there was a checkbox in the diffuse color / diffuse texture that is on by default (but can still be overridden) that says auto convert colors to physically correct values. It reminds me of a checkbox in the new vray blend material (in 3dsmax) that has a shellac button with a warning that it can create invalid results.
Linear Workflow
We could try to help, that Vray can be easy used as possible too.
I’m curious what Joe and Corey say.
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 
)
Linear Workflow
Fine, I’m curious.
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
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.
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?”.
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.
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. :shock:
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.
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.
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.
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?