Can Someone Help Me Understand "Display Corrections"? (And Maybe How To Save Them?)

[m_glisson]

Hello,

I've used V-Ray for 3DsMax pretty extensively in the past, though I've only just now started to use 5. One "Feature" I'm very confused about is Display Corrections, as shown in the V-Ray Frame Buffer. I first encountered this when I was rendering a series of images for a co-worker. I checked how they looked in a few test renders, I was pretty happy with them, and then I set everything up to render and save automatically. Come to find out the images turned out incredibly dark. Seems that I had to turn Display Corrections "Off" to see how the images would *actually* save (it was applying only one correction, a "Source RGB"). So my questions are:

1. What is the point of Display Corrections? As far as I can tell it shows you a nicer looking version of your render that you can't save out easily...
2. What is the "Source: RGB" correction exactly?
3. Is there anyway to save the image with the Display Corrections applied? It seems this should be possible since the "CTRL C" shortcut copies the image with the corrections still applied (this is what I ended up doing for my most recent project, and everyone was very happy with the result but it was a time consuming process)

I have done a good bit of Googling to try and figure this out, but I've yet to find a satisfactory answer (There doesn't seem to be a page called "Display Correction" on the Chaos Help Documentation, I've found "Color Correction" which I assume is related). I've also found a lot of discussion about using these corrections as a way to make sure the image is ready for another program, like Photoshop, but we don't use Photoshop, and are used to using images directly out of V-Ray renders.

[Muhammed_Hamed]

Hey m_glisson and welcome to the forum

What is the point of Display Corrections? As far as I can tell it shows you a nicer looking version of your render that you can't save out easily...

The "Display Correction" layer specifies the gamma/transfer function for the displayed image. Think about it as a "viewer" , it only affects how the rendered image is displayed but doesn't convert or change the pixels(scene-referred values)
Under this "Display Correction" you will have different layers similar to Photoshop's layer stack, could add layers like a Curve or Exposure..etc

What is the "Source: RGB" correction exactly?

This is part of the layer-based structure of the new Frame Buffer, the source layer determines the input of the layer stack. This is basically your scene-referred data, the actual pixels the renderer produced. There are 3 ways you can specify this source,
RGB >> which is the rendered image(beauty element) like what you had in the older frame buffer
LightMix >> if you want to build the rendered image(beauty) using light select elements (Light AOVs), so this mode allows you to adjust the intensity and color of your lights, during or after the render
Composite >> if you want to build the rendered image(beauty) using simple back to beauty compositing for example

Is there anyway to save the image with the Display Corrections applied?

Yes, your layers should be saved automatically, one exception is LUT layer which has its own "save in image" option
You could use Ctrl + C as well, if you share a screen grab of your layers it will be helpful to see why you are not getting a match

There doesn't seem to be a page called "Display Correction" on the Chaos Help Documentation

Here https://docs.chaos.com/display/VMAX/...playCorrection
And some helpful videos here https://docs.chaos.com/display/VMAX/...ckStart+Guides

but we don't use Photoshop, and are used to using images directly out of V-Ray renders.

Which is totally fine, you can rely on the frame buffer alone for that. Many studios do that
If you have more questions let me know

Best,
Muhammed

[^Lele^]

To add to Muhammed's excellent post, "display corrections" do precisely what they say: correct for the current display the image is being viewed on.
Data is calculated and stored linearly, but depending on the type of device one views it on (Monitor, Projector, Print, etc.), these corrections need to take place to ensure fidelity.
In other words, to counter the non-linear display device's characteristics, and show the data as it's meant to.

For most standard monitors, where linear workflow and color accuracy are important, you'll want it set to sRGB (i'm leaving OCIO/ACES aside on purpose, here.).
Depending on the image type saved (LDR vs. HDR), the correction may or may not be saved with the image to avoid precision loss at lower bit depth.
You can force the saving of the corrections by ticking the box in the Display Correction properties panel (you shouldn't, but you can, depending on your workflow.).

[stezza]

Any idea as to why I cant change the Display correction in VFB stuck on OCIO, what is preventing me from doing so??
Thanks for any help.

[^Lele^]

Any idea as to why I cant change the Display correction in VFB stuck on OCIO, what is preventing me from doing so??
Thanks for any help.

Max's own color management, if it's 2024 we're talking about.
Set that back to sRGB, and you'll have the "old" VFB behaviour.

[stezza]

Ah should have stated it's in SketchUp sorry, I did post in the forum but no luck, so thought I's try here. Maya is fine so I am having to render out from Sketchup then bring the VRIMAGE into Maya VFB to switch..at least its a workaround.
Thanks