Texture Color Space

[Steffen Dünner]

Hi there!

Right now (V-Ray for MODO 3.00.02) it looks like all textures are treated as linear color space, no matter if they're LDR (like PNG, TGA, ...) or HDR (EXR) and no matter if they're multichannel RGB or greyscale.
Are there plans to support the OCIO settings in the "Image Still" tab of each texture to make this consistent with MODO's color management?

Cheers
Steffen

[vlado]

I'm not sure about OCIO yet, I'm not thrilled about it, but we will definitely try to make sure that at least basic gamma stuff works correctly.

Even so there should be a way to change the gamma value of the textures for V-Ray, will get you more details on Monday.

Best regards,
Vlado

[Steffen Dünner]

OCIO in MODO still has some room for improvement, but it was a huge step from the former "we treat gamma 2.2 as sRGB" mess that caused a lot of surprises when loading your rendered images in Nuke.
For me it's mainly about consistency between MODO's renderer and V-Ray. Changing an image's gamma is already supported in V-Ray for MODO, yes.

Cheers
Steffen

[vladimir.nedev]

Our plan for this was to support the most common color spaces that we are sure can be applied quickly during rendering.
This means supporting only Linear, sRGB and maybe Gamma1.8 and Gamma2.2 (I am not sure whether these last two
only apply the specified gamma or do something more complex).

Do you use any other color spaces ?

Greetings,
Vladimir Nedev

[Steffen Dünner]

The mostly used colorspaces for me are of course linear and sRGB. My main concern is that the look&feel is consistent with the way it currently works in MODO 801, i.e. the "default" colorspace automatically makes an "educated guess" based on what the input format is (sRGB for 8- and 16bit LDR formats, linear for EXR, HDR). Then, if e.g. importing a normal map as LDR format, you can also tell MODO to use linear colorspace although it would normally default to sRGB.
I almost never ever used any of the other colorspaces MODO 801 offers (I used Cineon once or twice, but I could've converted these images before).

Cheers
Steffen

[vladimir.nedev]

This should be fixed in tomorrow's nightly build - the one from 2015-01-27. As well as in the next (3.00.05) open beta build.

Some notes :
- the recognized color spaces are
- sRGB, sRGBf, AdobeRGB - all considered sRGB and unclampled (I think MODO clamps sRGB, but doesn't clamp sRGBf)
- Gamma1.8
- Gamma2.2
- all other color spaces are treated as linear

- the default color space (8-bit, 16-bit or float) used should match MODO. Grayscale and .HDR images are always considered linear
(they don't use any of the "Scene" item's 8-bit, 16-bit or float color spaces), unless you specify their color space
to something different from "(none)" and "(default)".

- if an image is determined to be in sRGB space, but you also have a "gamma" in the texture layer that is not 1.0,
the sRGB transformation is approximated as gamma2.2, so it can be combined with the "texture layer" gamma in
one operation. This can be fixed, but it seems like a rare case, and I doubt the difference can be visible.

Also changing the colorspace channel in the "Image Still" tab will get updated in RT, but changing the default color
spaces in the "Scene" item will not.

Let me know if you run into any problems.

Greetings,
Vladimir Nedev

[Metzger]

I just loaded V-Ray for Modo up and I am scratching my head on how color is handled. Just so you know. .HDR images are always saved in sRGB. EXR is the only linear image format.


Does Modo detect what colorspace is what based on the image extension with OCIO? I really don't understand why Modo has so many areas for setting color.

I have the latest build and I am not getting a color match from Modo to V-Ray. Also, is V-Ray in Modo setup for a meters workflow or centimeters?

[vladimir.nedev]

In my tests MODO considers .HDR images to be already in linear space. And the results between MODO and V-Ray match in that case.

Maybe you've read it, but this MODO help page explains how MODO chooses which OCIO profile to use for a particular image :
http://modo.docs.thefoundry.co.uk/mo...anagement.html

Can you attach a scene(with the image maps) where V-Ray doesn't match with MODO ? By default MODO has GI enabled, so that is something to be careful about when comparing.

All distance parameters in V-Ray for MODO are in meters (unless explicitly specified in their label).
At some point I need to mark them as distance parameters, so you can enter and see them as mm, cm, etc.
This is only for convenience though, as internally MODO always stores distances in meters (it doesn't matter what unit system you choose).

Greetings,
Vladimir Nedev

[Metzger]

Here is the thing. Every single application that reads or writes HDR files saves it in sRGB. That would include Photoshop, Nuke, and every Realtime application like Unity or UE4. If you give UE4 a Linear .HDR file it will incorrectly display. Same with Marmoset in Unity. I think Modo needs to rethink it's color system and specify colorspace based on .ext

I setup the OCIO profile correctly. I am not using any textures for color testing but the default Background and shader for a sphere do not match in V-Ray on my end.

Good to know about the meters. Maya is centimeters so that's how correct DOF with the V-Ray Physical camera is calculated.

[vladimir.nedev]

Can you attach the scene that renders differently, I need to take a look at it.

Greetings,
Vladimir Nedev

[Metzger]

Hi Vladimir

Turns out the Physical camera being added automatically from settings was causing the color issue I was seeing. Looks like a match to me now. Thanks!

[vladimir.nedev]

Good to hear it works.
As for .HDR files I will leave it as it is, just to match MODO. At least there is a workaround for this, you just need to change the color space for the .HDR image from (default) to sRGB.
There have been some discussions on MODO's forum about the color management system, maybe they will implement changes for later versions.

Greetings,
Vladimir Nedev