LWF guidance needed.

[Tommy L]

Ok chaps, Im trying to learn LWF which seems the flavour of the month.

Ive followed Sawyers instructions available on his website and the results are rather nice. Well, they seem nice in the vray frame buffer with the sRGB button pressed. Im not entirely sure what this button does and would appreciate an explanation if someone has the time.

Also, when I saved out the image, it appears whatever the sRGB button has adjusted is lost. Any pointers on how to retain the sRGB adjustment?

Thanks,

Tom.

[JamesTaylor]

jsut a quick one... home time for me! and LWF would a long post! but there are few ways to retain the effect the srgb button creates.

 

1. in file save dialog box use the override gamma value

2. apply the gamma correction again in post (p'shop \ levels \ middle slider set to 2.2)

3. save as .exr file (floating point file format)

4. in vray colour mapping rollout change gamma to 2.2 (you won't need to use your srbg button in the frame buffer then. however, doing it this way is actually contradicting purpose of linear work flow so i'd suggest one of the 1st 3)

[Tommy L]

Cheers pal.

[alfienoakes]

Hey Tommy,

 

What a nicely timed post / switch over for you.. I am trying exactly the same thing. Problem is, I have 1.47 at work, and 1.5 at home.. anyway...

 

Have you calibrated your monitor? I read a few posts by Vlad that said if you are using an LCD, its best not to gamma correct it.. then I read somewhere else that its best too..

 

Well, I have gamma corrected my LCD to 2.2 (software correction) and changed my gamma in Viz to 2.2 and the input gamma to the same.

 

Using the Vray fb, I then apply my curve colour correction, which is the inverse correction to the gamma 2.2.. The images look a little washed out at the mo, but I think its a light thing.. It looks ok. brighter thou..

 

How is your set up going..?

[Tommy L]

OK....not great, but ok.

Essentially, I have only done a couple of things:

 

1) Installed the Colour Correct plugin (awesome)

2) use said plugin to alter my colour swatch materials to gamma 2.2

3) change the gamma and bitmap input gamma in 'Gamma and LUT' preferences to 2.2

4) Change the colour mapping in vray to Gamma Correction multiplier .454

 

I think thats it. My physical sun and sky settings now behave themselves ina much more obvious manner. Ive only tried a couple of renderings though.

 

Thing is Ive just started a new project, so once the modelling is out the way Im going to jump in with both feet.

[Crazy Homeless Guy]

4) Change the colour mapping in vray to Gamma Correction multiplier .454

 

i understand where .454 comes from, but i don't understand why it is being used here? ...out of curiosity, what format are you saving in?

[Nic H]

Im dying for a definitive tutorial on LWF.

 

Not all these half assed explanations scattered throughout the chaosforum

 

Id pay for it. A gnomonology 1 hr tutorial much like the image sampling one would be fantastic. Would negate the need to trawl through all the outmoded confused contradictory methods around.

 

Im sure alot of other people would be interested in this as well.

[kippu]

yes please +1 for the tutorial

[Geoffc]

yes please +1 for the tutorial

 

+2

[alfienoakes]

OK,

 

Please do not take this as a tutorial, as I am still getting to grips with this..

 

But this is what I have found so far:

 

I have gamma corrected my monitor to 2.2, software and by eye.

 

I have then changed my Viz settings to gamma correct 2.2, and the Bitmap inputs as well. This effects my material so colours display brighter.

 

Added 1 direct camera as sunlight, and added the environment as 1.2 multiple. No more lights are in this scene.

 

My colour mapping is now set to Linear multiply.

 

Activate the Vray frame buffer. This is important as you can apply correction to your image using this.

 

The image is rendered, and then in the vray FB, you can then apply the correction curve. This is to linearise the gamma curve. In the FB, check the colour corrections, and apply the correction curve. This will allow you to view the effects of the correction. Alternatively, dont worry about the curve, but save the file out an *.exr format. This will linearise the image for you. (from wjhat I understand.)

 

The images below show 2 things. Tha darker image is the render, without any correction applied, so saved straight out as Jpeg. The lighter one is with correction, so saved as an exr file.

 

As I said, this MY understanding of LWF. I may be way off the mark...

 

Now, if anyone has a greater understanding of this, and can point out anything, I would be gratefull to hear from you..

[Trevor Tizard]

This is by no means a tutorial, just how I use LWF:

 

Change the Viz/max gamma preferences to 2.2 and bitmap input gamma to 2.2

 

I render with the sun/sky system and physical camera

 

enable Vray frame buffer and use sRGB button

 

save images with a gamma 2.2 override

 

That's it!

 

FYI I have calibrated my LCD monitor, and I have to make my materials a little darker than before. This may not be pure LWF but my images have greatly improved and render a little quicker.

 

Hope this helps.

 

Edit: When I open the file in Photoshop I give the image a very slight "s" shaped curves adjustment - but Very slight.

[alfienoakes]

Trevor,

 

As someone who is already using LWF, (you..!) is my example:

 

A. looking about right.

B. working in the right way.ie setup etc..

[Trevor Tizard]

Hi Andy,

 

Your images look fine fella.

 

Your set up appears to be very similar to mine, the main difference being how you save the file from the frame buffer. I am happy to save .png files with a 2.2 gamma override.

 

In the original LWF post by Vlado he outlined three methods, thus there does not appear to be a difinitive "this way" but many routes to acheive the same thing - this is simply my preference.

 

Like other aspects of this kind of work the purists will tell you one thing, but others (myself included) will hit the print button when it looks OK.

 

Seems to me you've cracked it mate.

[alfienoakes]

Yep..

 

If theres one thing I have picked up, it appears to be there certainly is more than one way to skin a cat...!

 

The saving it to a png file with an override is indeed another way. Probably the best way to do an animation I would think, as saving a bunch of exr's would kill any network, and then lead to a lot of post work just to resave the file format...

[BrianKitts]

Im dying for a definitive tutorial on LWF.

 

 

 

I would start with Chris Nichols' Interiors DVD. It will get you started on LWF and he does about the best explination possible on the subject. (I'm not cutting him down.... it's really hard to explain.... he does a great job)

 

Beyond that it's not really a topic that someone can write you a "let me spoon feed you everything you need to know" type of topic. He explains the basis of it, why it's important and how it works, but you just have to dive into it to really understand it.

 

Between his dvd and the 100 posts on this forum and the net everything you need to learn is available.... not to mention the other info in the dvd that is really useful.

 

interiors dvd -> (good start to LWF and more)

http://commerce.vismasters.com/catalog/viewproduct.aspx?product=3677

 

exteriors dvd -> (this one actually comes first...also really usefull)

http://commerce.vismasters.com/catalog/viewproduct.aspx?product=3667

[Stephen Thomas]

As far as whether to save as 8-bit gamma corrected image (jpg, png etc.) or as 32-bit linear image (exr) goes, I think an analogy would be in digital photography where you have the option of working with jpegs or RAW images, with the latter capturing the full dynamic range of the scene but requiring tone-mapping for monitor display / printing.

 

If this is the case, when rendering to exr in vray should colour mapping always be set to linear then corrected by your image processing software?

[rivoli]

If this is the case, when rendering to exr in vray should colour mapping always be set to linear then corrected by your image processing software?

 

if you're working linearly yes. color mapping has to be linear and gamma has to be left at 1.0 (exr being a linear format having any other value will double correct your images).

in newer builds (not yet released), there's an option to tell vray to gamma correct without altering the colours but only the sampling. this is very good for a couple of reasons: you can keep a totally linear workflow with full float outputs, and have vray doing the best sampling and AA because it knows you're rendering with a 2,2 gamma correction.

[Burgerlim]

Hi, Newbie here..

Been trying hard to work in LWF, some question, when enabling gamma correction in Max/Viz, realise color become pile and been very hard to get a black color materials. is this normal? no matter how hard i try to get a black color laminate, it turned out grey! (tried with color correct plugins)

setting.

1. prefference -> Gamma -> 2.2 (input = 2.2)

2. Enabled vray sRGB space.

 

another issue is monitor calibration, when try to apply icm profile.. color becomes washout. (and understand from papers that gamma curve for LCD monitor is curved downward. while profile correction is to curved upward.. so as to invert to linear) but it just look wash out...

 

Thanks for any advise...

[rnx]

I would start with Chris Nichols' Interiors DVD. It will get you started on LWF and he does about the best explination possible on the subject. (I'm not cutting him down.... it's really hard to explain.... he does a great job)

 

Beyond that it's not really a topic that someone can write you a "let me spoon feed you everything you need to know" type of topic. He explains the basis of it, why it's important and how it works, but you just have to dive into it to really understand it.

 

Between his dvd and the 100 posts on this forum and the net everything you need to learn is available.... not to mention the other info in the dvd that is really useful.

 

There is also a tutorial by nichols on compositing which is based on linear work flow, this with the bathtub rendering. I can't recall where it's available. But his point of course was that you do not gamma correct in the LWF. The various passes he rendered out in unclamped open EXR, he comps in nuke.

great tut.

[alias_marks]

Found this tutorial that sheds some light on the issue, no pun intended:). Still would eventually like more detail, but a good start.

 

http://www.gijsdezwart.nl/tutorials.php

[Stephen Thomas]

Found this tutorial that sheds some light on the issue, no pun intended:). Still would eventually like more detail, but a good start.

 

http://www.gijsdezwart.nl/tutorials.php

Thanks for the link Mike, I've been getting to grips with this recently and this helped me to understand the thinking behind the process.

 

I would say I am using the technique shown in figure two of the tut, mainly because I work from an existing library of materials. Also, surely to manually convert all my textures to linear colour space for input to max isn't any different from letting max do this for me. True linear workflow, as shown in figure 3 of the tut would only apply to textures created from linear data e.g. raw camera files, I imagine.

 

Anyway, the method I use is as follows:

 

- Turn on Max's gamma correction at 2.2

- Set bitmap input gamma to 2.2, check affect material editor, don't check affect colours (does this negate the need for colour correct plug-in, not sure?)

- Set output gamma to 1.0

- Leave colour mapping settings at Linear, all at 1.0

- Render to vray frame buffer

- Click sRGB button

- If saving as open exr, leave output gamma at 1.0

- If saving as 8-bit image (tif, jpg, png) use override gamma at 2.2

 

This seems like the most straightforward option to me as you don't need to alter your existing materials and no messing about with colour mapping.

 

The only problem I have had is with the dreaded black outline around bright areas which is an antialiasing issue. The only way I can rectify this is to check sub-pixel colour mapping and clamp output in colour mapping settings. However, as this clamps the whitepoint to 255 this only allows output in 8-bit format.

 

Just my experience so far, hope this helps someone!

[alfienoakes]

Hi, Newbie here..

Been trying hard to work in LWF, some question, when enabling gamma correction in Max/Viz, realise color become pile and been very hard to get a black color materials. is this normal? no matter how hard i try to get a black color laminate, it turned out grey! (tried with color correct plugins)

setting.

1. prefference -> Gamma -> 2.2 (input = 2.2)

2. Enabled vray sRGB space.

 

another issue is monitor calibration, when try to apply icm profile.. color becomes washout. (and understand from papers that gamma curve for LCD monitor is curved downward. while profile correction is to curved upward.. so as to invert to linear) but it just look wash out...

 

Thanks for any advise...

 

The attached shows LWF with some dark reds and a black sphere. As you can see, the black sphere does not look washed out. If you have a lot of reflection on your black, that could make it look grey.. This is straight out of Viz, saved as exr, then saved as jpg in p'shop.

 

No post production at all.