Does Vray Sun Have to Be Used With Linear Workflow?

[wizuby]

Seems like the environment is pretty dark. Does it have to be used with LWF?

[aaronrumple]

Are you using a vray physical camera? If not - you should as it offers the exposure control you are looking for.

 

Of course you should be using LWF as it will produce most dependable results - but you don't have too.

[alfienoakes]

Also, dont assume that you SHOULD be using LWF.. you will find there are plenty of people that dont use it, and are happy with the results.

 

It is quite a deep subject, so worth having a look at in some depth. You could use LWF with or without Vray sun, and you could use Vray sun with or without LWF....

 

But if you are using Vray sun, and physical cameras, then read up on them, as there are many settings to give you varied results..

[aaron-cds]

If you're using the vraysun / sky / physical camera, I strongly recommend the .255 method by Lele. I've moved on to the .3 value with the new 1.50.00 in order to get the correct sky colors again. The value of this method is that it will shave off 20% of the render time from the LWF (inverse gamma .4545). It also produces cleaner shaded areas.

[Crazy Homeless Guy]

It is worth noting that the whole LWF things is about

getting accurate display data on your monitor and is

not really tied to whether or not you are getting desirable

exposure values in your renders. (Although the two can

be tied together)

 

Regards

Bri

 

not necessarily tied to exposure, but LWF also creates closer to reality color bleed off of materials, and speeds your rendering time.

 

....both of these are possible because you need less light intensity to illuminate the scene. less light intensity means the rays are not carrying as much color information, a.k.a. what creates color bleed. less light intensity means the scene renders faster because when you increase the amount of light bouncing around the scene, you increase the amount of time it takes to render that scene,

 

yes, LWF is not necessary, and may create several headaches of its own beyond just understanding how it operates.

[alfienoakes]

If you're using the vraysun / sky / physical camera, I strongly recommend the .255 method by Lele. I've moved on to the .3 value with the new 1.50.00 in order to get the correct sky colors again. The value of this method is that it will shave off 20% of the render time from the LWF (inverse gamma .4545). It also produces cleaner shaded areas.

 

Aaron,

 

Bit of a diversion from this thread, so apologies, but;

 

I thought, and maybe incorrectly, that the first thing Lele did in his video was to change his gamma in preferences to 2.2, as per the LWF method. But you mention that you are using his method with .3 with 1.5, and that it is a different method to the LWF.

 

I assume that the .3 is your interpretation of the .255 method, and that 1.5 is Vray latest version.

 

I thought Lele's method was a derivative of the LWF method, but now sort of updated to make working with the physical sun more realistic in 1.5, ie sky colours and intensity of shades etc.?

 

Just want to clarify as its a weighty subject ..

[aaron-cds]

I assume that the .3 is your interpretation of the .255 method, and that 1.5 is Vray latest version.

 

I thought Lele's method was a derivative of the LWF method, but now sort of updated to make working with the physical sun more realistic in 1.5, ie sky colours and intensity of shades etc.?

 

Just want to clarify as its a weighty subject ..

 

.3 was my interpretation in a way. I interpreted the sky color to be different using .255 in 1.50.00. After playing around I finally arrived at the conclusion that I could change the multiplier from .255 to .3 in order to get a similar sky color and exposure to what I was getting with .255 in 1.5 rc3. The principles remain the same, I just tweaked one of the modifiers.

 

I used to set inverse gamma to .4545. Now that I'm using the lele .255 method in 1.50.00, I'm still saving 20% of the rendering time. That's reason enough to keep using it.

[mik3]

Linear Work Flow? Can anyone send me a link about this topic.....and about Lele's script as well? What does it do? Ta everyone!

[gfa2]

Linear Work Flow? Can anyone send me a link about this topic.....and about Lele's script as well? What does it do? Ta everyone!

 

You really need to check out the Chaos forums...there is just so much info to read and digest, it would be pretty silly to try and explain it all here.

 

http://www.chaosgroup.com/forum/phpBB2/viewtopic.php?t=17824&highlight=lele

 

This is just one of many concepts or techniques in the whole LWF world.

[alfienoakes]

.3 was my interpretation in a way. I interpreted the sky color to be different using .255 in 1.50.00. After playing around I finally arrived at the conclusion that I could change the multiplier from .255 to .3 in order to get a similar sky color and exposure to what I was getting with .255 in 1.5 rc3. The principles remain the same, I just tweaked one of the modifiers.

 

I used to set inverse gamma to .4545. Now that I'm using the lele .255 method in 1.50.00, I'm still saving 20% of the rendering time. That's reason enough to keep using it.

 

Makes sense. I have viewed Lele's tut'. Problem was it crashed out on the final 3rd, probably where all the good bits are. Downloaded it from another source, so going to have another look at it now.

 

Working on LWF at the moment, and it does make all the scenes much easier to work with, so hopefully, after looking at Lele's again, should be another leap forward..

[Crimsus]

Ok, here's the trouble I have run into.

 

I have setup 3DS Gamma & LUT to use 2.2 Gamma, 2.2 Bitmap Gamma Input, 1.0 Bitmap Gamma Output, plus Affect Material Slots in editor. Basically, everything you would typically do to set up a linear workflow in 3DS.

 

I have done several great still shots but now here is the trouble I am running into. If I do an image as a still, I can use the VRay Frame Buffer (VFB) to adjust the curves and get the right image. Feeling satisified with the still shots I then moved onto making a small animation (which isn't really an animation, it's just a 100 frame long still shot) and save it as an AVI. The problem is when I open the AVI, the image is VERY much darker than what I had in the VFB after adjusting the curves. I want the AVI color to match exactly what I have in the VFB. To ensure I am not losing any information I am saving the AVI Uncompressed.

 

The only solution I have been able to come up with is going into the Renderer options, going to Color Mapping, selecting Gamma Correction, and setting the Inverse Gamma to .4545. Now the still shot doesn't need any curve adjustments and the AVI color is close, but if I bring up the still and the AVI using the RAM Player, I can still see that the AVI is a tad darker but only by a very small margin.

 

Does anyone have some hints on anything else I can tweak so that the AVI and VFB still shot colors are identical?

 

I have considered just giving up and correcting my future AVI's when I start compositing them with live footage but I'd like to avoid that because I fear I might lose some of the color information and the end product won't be as nice as I want it to be.

 

Edit: My monitor is calibrated, although from what I understand calibrations are merely to ensure color correctness of the display itself but monitor calibrations are not intended as a "fix" for ensuring linear color space in CG.

 

v/r

Crimsus

[kippu]

does the same happen if you save as sequential images and then compile them using premiere or after effects or anything similar?

[Crimsus]

does the same happen if you save as sequential images and then compile them using premiere or after effects or anything similar?

 

Ok, here's a kicker. This problem only happens when I am using Video Post. If I render the AVI footage directly to an AVI (uncompressed) without using Video Post, the colors are perfectly matched. If I use Video Post, then the color information loses some of its intensity. I did this by accidentally forgetting to use Video Post for an effects shot and I used the standard Render dialog for the footage.

 

VERY odd, but then again, Video Post wasn't designed to be used as a legitimate post production interface.

 

Can someone else try this and see if they get the same weird results?

 

-Crimsus

[MasterZap]

Ok, here's the trouble I have run into.

 

I have setup 3DS Gamma & LUT to use 2.2 Gamma, 2.2 Bitmap Gamma Input, 1.0 Bitmap Gamma Output, plus Affect Material Slots in editor. Basically, everything you would typically do to set up a linear workflow in 3DS.

 

Your error: Your image output gamma should also be 2.2, so you get a "what you see is what you get" when you save files.

 

Output gamma should be 1.0 when writing to floating point files only.

 

 

As for the original question, I'd say always use linear workflow, unless you are doing some kind of oldschool cartoon rendering. Regardless of renderer.

 

And if your input is real world physical values and colors, like IES lights with kelvin temperatures, or better yet, a spectrally created sun&sky simulation, then using linear workflow is more important than ever!

 

So the answer to the original question is an undoubtable and absolute YES.

 

/Z

[Crimsus]

Output gamma should be 1.0 when writing to floating point files only.

 

So for the purpose of rendering animations I should be using an Output Gamma of 2.2 instead of 1.0 since AVI's don't utilize 16-bit?

 

Off topic: Are you stalking me from TFN?

 

v/r

Crimsus

[alfienoakes]

 

So the answer to the original question is an undoubtable and absolute YES.

 

/Z

 

That is not completely true. Yes, it is a better way of doing things, but there are other methods to get the 2 working together. I have set up a scene with physical camera and sky, and NOT used LWF, and achieved the results I wanted to achieve.

 

It will actually work better if you use the .255 method discussed over on Chaosgroup, but that is not the ONLY way it will work. The understanding comes in how the physical camera and sky work together.

 

But I do agree with what Masterzap is saying, that it is a better way to work.

[Crimsus]

What should I use for my gamma if I am rendering my footage as an AVI/Uncompressed? Should I set my inverse gamma to .4545? Should I set my Output Gamma to 1.0 or 2.2?

 

v/r

Crimsus