LWF (linear work flow)..

[shikodesign2000]

Hi,

 

Can anyone tells me a brief explanation of LWF (linear work flow)?

 

What's its purpose??

[JamesTaylor]

if you do a search on these forums for Linear Work Flow you'll find plenty of information to explain it. There are many threads on the subject, its a very well covered subject.

 

another good place to seach would be the chaos forums.

 

Once you've read those if you still have question ask....!

[Crazy Homeless Guy]

an explanation of LWF is anything but brief, and understanding the process will take some effort on your part.

 

in short, the purpose of working in LWF is to equalize the gamma curve your monitor has, which is typically a 2.2, though it is different if you are on a mac. equalizing the curve has a couple of advantages. the most important of these advantages is to give you proper color, and color bleed in your images. say you have a red box against a white wall, and you have a typical setup without LWF. what is going to happen? the red from the box is going to bleed reflected color all over your white wall. ...more reflected color than you would have if you actually had a white wall with a red box against it in real life. when working creating visuals in LWF you are using less light to illuminate a scene than you would if you were using a typical setup. this means that in LWF the lighting hitting the red box has only a fraction of the intensity. ...because the intensity of the light is not as strong, the reflection from the light is not as strong. meaning, that the color bleed onto the wall is not nearly bad. the reflection of the red box in LWF imitates the reflection of light in real life to a closer degree than the reflection of the red box in a non-LWF or typical setup.

 

now, this starts to tie into the other advantage that LWF offers. the more light you have in a seen, the more calculations your computer needs to do to resolve the light. the less light in your scene, the faster the image will render. so we use less light to increase render times, and get accurate color bounce.

 

so, now you have a dark image... but if you apply the gamma curve back to take your image out of LWF, it will appear correctly on your monitor.

 

there is one disadvantage to LWF, but i don't think it i enough to equate not using it. with LWF, your images will be noisy because you are working with less light, so you need to up a few of you GI engine settings to counteract that,

 

when working in LWF you are also typically working in a floating-point 16 or 32bit color space. so you are making the jump from 8bit imagery into images with a lot more information in them. so that gives you some advantages also. some people choose to 'burn' the gamma into their image early on, so they are not working with greater bit depths.

 

....now we are starting to get into greater depth, and that is where your research needs to start.

[womble]

Theres just so much information to this subject and so many contradictory methods and explanations put forward by people that it makes it incredibly difficult to know where to begin. I like CHG's post as a brief introduction, however i'm quite positive that the first person in the CG industry to produce a well written, consice tutorial website or DVD that really just holds your hand through making sure you have all your settings done correctly (including information on setting up your monitor) will make a lot of money.

 

There are several well referenced tutorials on the internet (especially on the chaosgroup forums) but I just find that a lot of these contradict each other and are never really definative.

 

I know that I, and probably a lot of other people would pay good money just to be told 'do this, this and this and you will be working in LWF'.

[Thablanch]

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

 

Quite well explained in this tutorial.

[bjornkn]

The HDRI handbook covers this quite good, and is easy to understand/follow.

He also writes that one of the disadvantages of LWF is that you don't see what your'e doing until it is finished and gamma corrected. "No more eyeballing allowed", as they write. All textures need to have their gamma stripped out, and all all colors etc need to be converted into linear space, like setting 50% grey to 18% grey.

Sounds like a lot of hassle...

[BrianKitts]

I know that I, and probably a lot of other people would pay good money just to be told 'do this, this and this and you will be working in LWF'.

 

That's great in theory to get you started but if you do what you do cause someone told you to.....when you run into a problem, if you don't know the process and what you are doing how will you ever be able to troubleshoot and fix your problem... other than bugging the guy who set it up for you.

 

For instance if you are saving out your images and all of the sudden they are all washed out in photoshop, is it because A. your gamma output level is wrong in 3dsMax, B. your gamma level in your rendering engine is doubling the max settings, C. you saved to JPG in 8bit as opposed to an EXR or TIFF in 32bit and photoshop isn't applying an adjustment curve.... OR D. this is a multistep process and if you slip up one step ..... would you need to apply a gamma correction in photoshop of 2.2, or .4545?

 

 

Ever hear the one about giving a man a fish?? It's worth taking the time to learn the process even if it makes you beat your head against the wall for a couple of months.

[Thablanch]

Well, kind of hard to really understand what it is at first, but when I do re-open older projects that were not done this way, I do see all the avantages of working LWF. Plus, since 1.5xxx came out, the gamma stuff is way easier to do than in previous version, you have a gamma rollout now, so whatever color mapping mode you are in, you can do it, even without mastering / understanding it totally...

 

Then again, it is just a workflow, some amazing results were made with it, some without.....

[shikodesign2000]

Thank you very much for all of you my friends, your valuable information will help me ofcourse as a main guide in this topic..

 

Thanks again, and I'll get back to you once a reach a good results.

[shikodesign2000]

I just want to reply on (James Taylor), that maybe he thought I'm lazy guy and I want easy way to get information!!

 

In fact I'm not this person at all, but now I have very little time to read and train on tutorials, but I like to do this very much, and I beleive this's the only proper way to understand things better, my only way is in my free time.

 

Also, I just asked about (breif explanation), just a title, to be a guide, no more, not detailed topic, but I'm thankfull again for all who gave me detailed imformation.

 

Just want to make things clear.

[Peter M. Gruhn]

[give a man a fish] Sure, but it's nice not to have to build up a functioning method from nothing especially when so doing involves ... not knowing why it isn't working. "Why is my picture black?" Well, there could be any number of things and once you've got your masters in "fishing" you can start to analyze it. If, instead, you start from a functioning template you can learn how changes in it work; you can compare that sudden washed out image's settings to your "known good" settings.

[JamesTaylor]

Sherif,

 

the reason i suggested searching here and chaos group forum is that this question / topic seems to be asked about once a month for the last 12 - 18 months. As a result there is plenty of info available by way of a simply search that i'm sure would have answered your question and given you a basic overview of LWF.

 

I did not imply in anyway that you were lazy, i simple pointed out to you that there would be plenty of info available regarding LWF if you did a search, i even suggested 2 good locations to search.

[Crazy Homeless Guy]

i blame chris nichols for the entire LWF mess in the arch viz community. before his DVD all of us dimwits had no idea what it was.

[Sawyer]

A few years ago I put together a tutorial on LWF. Its pretty dated as I haven't updated the vray aspects of it for a while and the program has changed but you can DL it at:

 

 

http://sfrendering.com/index-login2.html

 

 

pass - vray

[Ernest Burden III]

Thanks. I'm working on understanding vray colormapping (CM) right now. The standing suggestion is to use a gamma of .4545 to invert the built-in 2.2 gamma bias. OK... But then you have tonemapping/colormapping settings that behave differently in vray than they do in C4D (my host app), so its tough. I'm running a test where CM dark/bright setting animate from .5 to 10 so I can look at a range of setting at once. I wonder what I'll learn.