How to get better VRay renders (aka working in linear space)

[czoog]

Btw, the link in the first post is dead and needs updating if anyone has a working one handy..

cheers

This one works:

http://throb.net/site_main/LinearWorkflow.html

[jujubee]

*deleted cause I skipped through previous posts...*

[panthon]

I have tried this workflow with the new OPENEXR support in max 8, but i´m a bit confused about it. Can anyone describe a little step by step of VRAY-to-Combustion pipeline? Or maybe VRAY-to-Photoshop via EXR. I don´t really know how to setup these applications in order to get the correct gamma, exposure and so on, specially when it´s concerning to LUT editors... (Log to linear, linear to log, straight, etc...)

By the way, anybody got experience with OpenExr and nuke? Combustion at the moment doesn´t support DOF, REnderid, MAterialID, etc channels via exr

[samuel_bubat]

That´s an interresting tutorial !!
I used to post process images in a similar way.. with the only difference that
i use more or less photometric lights.A Direct with a multiplier of 50 and an
environment background with a multiplier of 20.
(I could use IESSun as well.. but I use Directs cause they support caustics)
I than used gain/gamma/saturation/ to "adjust exposure".
This is an example
http://sorceress.netfrag.org/optix/_Post_Exposure.jpg
http://sorceress.netfrag.org/optix/_sun_a0000.jpg
Now my question... if i work in linear space with multipliers not higher
than 1 ... would it be still possible to get physical accurate results with the
right curve adjustments ? Or is there a difference in the light distribution
when i use lights with very high multiplier to simulate the energy
of an sunlight... for example ??

[panthon]

Hey, Samuel, how do u manage to get the detail back from the washed out bright areas of the image using a RPF? What application are u using to postproduce your image?

[Sawyer]

So this is it now. Use Gamma Correction color mapping Bright 1, Dark 2.2.
In Preferences use gamma correction at 2.2. And turn off apply curves on the Vray FB. Is that it? Is this correct linear color space?

edit - or was that 1/2.2? 1 over 2.2 = .45454. for bright?

I see - I think. Actually that looks better. Never mind.

[Gijs]

Sawyer, if you use gamma correction colormapping, use bright=1 and dark=1/gamma.

[EDIT] keep dark =1 and bright 1/gamma [/EDIT]

Although most people think their system gamma is 2.2, this is not neccessarily true. If you have not calibrated your system, the native gamma is somewhere between 2.4 nd 2.6 depending on your monitor.

I recently read a lot of interesting stuff on http://www.aim-dtp.net. You can read about several problems when editing in gamma corrected colorspace. So also in photography linear seems the keyword in quality editing. There are many comparisons between linear edited images and images edited in gamma corrected color space. Highly recommended reading!

[Sawyer]

Thanks Gij's that makes sense. I did what was not recommended to do & I went into some files I am working on right now and change to this color space and it really really helps. I had a scene where I had a large black shadow and it was just black. Now it looks like a shadow gradually getting darker away from the sun.

I wish I had done this sooner.

[cpnichols]

Sawyer, if you use gamma correction colormapping, use bright=1 and dark=1/gamma.

Although most people think their system gamma is 2.2, this is not neccessarily true. If you have not calibrated your system, the native gamma is somewhere between 2.4 nd 2.6 depending on your monitor.

This is true in part. Part because your monitor is not always 2.2, but not true because you should adjust your monior (manually) to be set to 2.2, meaning that it should match an sRGB curve. It is best to keep your rendering set to a standard, and make sure your monitor is set to match that standard.

That way, when you look at it on an other monitor which is set correctly as well then it is good. Otherwise, you will force other to try to adjust their monitor to 1.8 or 2.6 or whatever.

That is why in the VFX world, lighters and compositors have their monitors professionally calibrated every month, so that we are all looking at the same thing. Monitors drift out of calibration. The older they are the faster they drift. LCD monitors are horrible to calibrate, are never accurates, and have horrible blacks.

[throb]

LCD monitors are horrible to calibrate, are never accurates, and have horrible blacks.

actually lcd monitors calibrate quite easily (gretag macbeth and the colorvision tools are great for this)
they are pretty damned accurate for color but NOT for black levels.
the dell 24" monitor i have is really accurate except for the blue. it's too strong in the blue area. can be fixed with a 1d lut of course!

black level is the biggest issue facing lcd but since nobody makes crts anymore we need to learn to work with them as much as possible.

[Sawyer]

Wait

SV,
To get the output right away (thus the curve burnt into your image) use the gamma correct color mapping, set bright color map tp 1/2.2 (about 0.45454) and render to Vray Framebuffer. Your RGB color channel will be the corrected image, your RealRGB channel (if selected in GBuffer output channels) will remain unaffected

And -

"Sawyer, if you use gamma correction colormapping, use bright=1 and dark=1/gamma. "


Those seem contradictory. I want to make sure I have this right. Thanks

[Gijs]

Sorry about the confusion. You should use dark=1 and bright=1/gamma. I've edited the wrong post.

[Gijs]

This is true in part. Part because your monitor is not always 2.2, but not true because you should adjust your monior (manually) to be set to 2.2, meaning that it should match an sRGB curve. It is best to keep your rendering set to a standard, and make sure your monitor is set to match that standard.

That way, when you look at it on an other monitor which is set correctly as well then it is good. Otherwise, you will force other to try to adjust their monitor to 1.8 or 2.6 or whatever.

I agree that it is best to match your monitor to a certain standard, but I mentioned it, because maybe some people think that without calibration your monitor has a gamma of 2.2.

A gamma of 2.2 btw, is not the same as sRGB. It seems that the sRGB is a far more complicated formula than a simple gamma curve.

I can't speak about what's right for the film industry, but for many photographers, sRGB is certainly not the way to go, since it has quite a small gamut.
I recently read that CCD's in contrary with analog film, have a linear response to light by nature. The low end digital camera's mostly convert this linear capture to a sRGB jpg, whereas professional camera's have the option to save the raw (linear) image.

Shortly a program called LightZone will be launched for windows also(currently only available on mac platform), which claims to be working in linear space. I am looking forward to see what it can bring to linear renderings. But even before that program will be lauched, I discovered that in Photoshop, by assigning a linear profile to a rendering, you can look at it as if the gamma curve was applied. I am now using this technique to load the (linear) openEXR into Photoshop.

[thablanch]

Kinda get it, but stupid question now:
How can I use that with the renderfarm, as the Vray frame buffer is not avaible fon an image that was premade elsewhere

[throb]

Kinda get it, but stupid question now:
How can I use that with the renderfarm, as the Vray frame buffer is not avaible fon an image that was premade elsewhere

the renderfarm won't affect your gamma settings at all.
we use this on a renderfarm all the time with great success.