Linear workflow wrong?

[michae]

So when I set up my vray setting for LWF Ive always check on Linear "Workflow" which seems to work and give me correct results. But in documentation it says "Note that this option is intended to be used only for quickly converting old scenes which are not set up with proper linear workflow in mind. This option is not a replacement for proper linear workflow." Should I not use the "LWF" option? What is the difference between checking on "LWF" vs manually adding a gamma node or extra attribute to the file texture.

Thanks,
Michael

[vlado]

Ideally, gamma (or sRGB) correction should be done only on File textures used as colors, and not on colors in procedural textures, results from procedural textures, bitmap textures used for bump and displacement etc. This is the correct workflow.

The "Linear workflow" option in V-Ray does something slightly different - it applies the gamma correction to the final result of the shading networks connected to the color slots of the VRayMtl materials, regardless of how those colors are computed (e.g. they are solid colors, or they come from File textures or from some other procedural textures). This is a quick hack to get a useable result if you have a scene that was not created with linear workflow in mind. However ideally it would be preferable if you stick to the first method right from the start.

Best regards,
Vlado

[chuckie7413]

Hi Michael.

A really great script has been released by artist Goran Vinterhalter.

Here is the link to download the script:

http://www.sendspace.com/file/77ex2m

He also made a video of how to use the script.

http://www.vimeo.com/21275415

Check it out.

Looks like a really great script. I will be using it in future projects.

Best,

Rich

[michae]

Ideally, gamma (or sRGB) correction should be done only on File textures used as colors, and not on colors in procedural textures, results from procedural textures, bitmap textures used for bump and displacement etc. This is the correct workflow.

The "Linear workflow" option in V-Ray does something slightly different - it applies the gamma correction to the final result of the shading networks connected to the color slots of the VRayMtl materials, regardless of how those colors are computed (e.g. they are solid colors, or they come from File textures or from some other procedural textures). This is a quick hack to get a useable result if you have a scene that was not created with linear workflow in mind. However ideally it would be preferable if you stick to the first method right from the start.

Best regards,
Vlado

Thanks, I understand now. This isnt a vray question but are the procedural textures and the color swatches(solid color) we see and create in maya linear or srgb?

Thanks,

Michael

[vlado]

This isnt a vray question but are the procedural textures and the color swatches(solid color) we see and create in maya linear or srgb?

Procedural textures are always linear. Maya 2012 may have an option to show gamma-corrected swatches for display, but I'm not quite sure.

Best regards,
Vlado

[MoonDoggie]

Do not use that tickbox (it's a dirty fix for "converting" old scenes). If you want to do it correctly, set it up the way that's suggested.

[Metzger]

Yeah, I feel like the linearworkflow button should be removed.

First set your Colorspace to linear multiply and gamma to 2.2 That means you will sample knowing that you will be viewing everything with a 2.2 srgb viewer lut.

Then you want the affect swatches option ticked on so your shaders are displaying correctly Remember, you want all color and sampling calculated in linear. If you are using linear exr's make sure they are linear. Some 2D software like to save a SRGB lut embedded in the exr. I I think Photoshop does that and Mari Definately does that for exr writing in version 1.2. It will be fixed in 1.3.

If you are using an imageplane, or any 8bit textures that have a srgb lut embedded, then you need to select the file node then go Vray attribute, and add the Bitmap input gamma. If you use the Maya framebuffer, make sure on the Vray Common tab that you have convert image to srgb for renderview. If using vfb viewer, make sure srgb button is turned on.

I really think the default Maya globals should be setup for correct linearworkflow and Adapative DMC with linear workflow button removed, but that's just my opinion.

Also, if you are unsure what the colorspace is on your images, you should load up a copy of Nuke since there is no other program for 2D that will give you a better understanding for color that that.

Once again, this is all personal opinion. If you have exr's with an embedded SRGB lut, you can read them in srgb, and write them out linear exr. Just make sure that your color looks correct with an srgb viewer lut.

[snivlem]

*nevermnid*

[michae]

I understand LWF and the reasoning behind gamma correction. Im still a little cloudy when it comes to what I view in maya. I made a image to describe what I think is correct, please correct me if I am wrong.

http://img695.imageshack.us/i/srgb.jpg/

[snivlem]

So yeah still not sure here.

Thanks Metzger but there are still some holes that I'm not sure of:

The only consistent result I can get without using the "Linear Workflow button" is a complete washout. No matter which script I use, which setting I have in V-Ray or which display profile defaultViewColorManager is using.

Oh well

[pxm-vray]

So yeah still not sure here.

Thanks Metzger but there are still some holes that I'm not sure of:

The only consistent result I can get without using the "Linear Workflow button" is a complete washout. No matter which script I use, which setting I have in V-Ray or which display profile defaultViewColorManager is using.

Oh well

that's because you are not using linear textures.

[sharktacos]

I for one really like the linear workflow button. Please keep it!

Linear workflow can get quite confusing, but the basic concept is quite simple:

1) remove the gamma on you color textures
All images on your PC have a gamma of 2.2, so setting the gamma to .455 puts it back to 1.0 (1 ÷ 2.2 = 4.55).
You can do that by ticking the "linear workflow" checkbox. Or if you prefer, you can do it manually on all your color textures by adding a gamma adjustment to them.
2) render in linear
For this you need to set the gamma to 2.2 in the color management
3) view that render in SRGB space
Computer monitors cannot view linear images because they all gave a built in gamma adjustment (2.2 on a PC). So you need to view it as sRGB even though it is linear. Otherwise it will look washed out.
You can do this with the "convert display renderview in sRGB" tickbox. There's also a sRGB icon in the VFB to the the same thing.

If your picture looks washed out, or too dark, you are missing one of the above steps.

[aweidenhammer]

I'm in general agreement with Scott... though I would avoid removing the linear workflow button, as that would cause incompatibilities with older scenes where it is used.

Renaming it to something less enticing to use would be ok though Not sure what that would be... but the best workflow is to apply gamma compensations only where needed. I will say, not everyone uses Nuke, so forcing a workflow where everyone uses linear images isn't a practical requirement. I understand other progs can remove the gamma as well, but the point is that most renderers will have to deal with srgb gamma images for some time to come. Making an easy, mostly functional way to handle it is a great advantage to Vray over competitors.

Andrew

Andrew

[sharktacos]

The only consistent result I can get without using the "Linear Workflow button" is a complete washout. No matter which script I use, which setting I have in V-Ray or which display profile defaultViewColorManager is using.

Also let me mention that Maya's color management display profile (under display in the render view window) is incompatible with vray. You need it for Mental Ray to view the images as sRGB, but not in vray since this is done (with a better implementation that avoids banding on 8 bit images) with the "display as sRGB" option in the vray globals. If you have both on it will do a double gamma which looks washed out. So keep it set to sRGB display and sRGB profile, and turn off color management in the Maya globals.

Speaking of which, it is worth mentioning that while the color management in Maya (in the render settings) is hopelessly broken. It does a gamma indiscriminately on all images meaning it will break things like normal maps. The vray "cheat" is much more intelligent, since as Vlado said, it only does a gamma on things being used as a color input on a shader, which means that 95% of the time it is right, and for those 5% you can add a gamma node to compensate (putting occlusion into the overall color of a SSS shader for example). So I'm not really sure why it gets such strong objections since it works pretty darn well. Do people also want to remove the same button from Max?

[Metzger]

Washout how so? Diffuse textures or lighting in general? If its lighting, well.. welcome to linear workflow. That's the whole point of using linear workflow for lighting. You need to adjust your lighting. If your textures are washed out, are you using 8bit images and applying a vray gamma input node? Are you using exrs? If so you probably have a double lut happening with the exr having an srgb gamma included in the file which is wrong. I use Maya 2009 so I don't mess with the new color management in Maya 2011. Post a zip with textures and a scene file. I will check it out for ya.