Aces

[Dave_Wortley]

I'm starting to look into the ACES work flow, I was wondering if there are any plans to add any native LUT support from VRay? It does appear that ACES might be the new 'accepted' standard......

[vlado]

V-Ray does support LUT files natively in it's VFB and through the VRayLUT texture. I don't think you need anything else from us for the time being, as far as LUTs are concerned.

We do plan to add a switch for the internal spectral color space though, because stuff like light color temperature, sun&sky, dispersion etc. must be transformed into ACEScg if you plan to use ACES.

Best regards,
Vlado

[Dave_Wortley]

Yeah I was wondering about a dedicated ACES button or drop-down button to switch from sRGB-to-ACES in the VRayVFB if this is the 'new standard'.

[vlado]

Yeah I was wondering about a dedicated ACES button or drop-down button to switch from sRGB-to-ACES in the VRayVFB if this is the 'new standard'.

For the time being, it's best to just use a suitable OCIO configuration.

Best regards,
Vlado

[sharktacos]

For the time being, it's best to just use a suitable OCIO configuration.

Best regards,
Vlado

Would this be the correct .ocio file to load into the VFB?
https://github.com/imageworks/OpenCo...ter/aces_1.0.1

We do plan to add a switch for the internal spectral color space though, because stuff like light color temperature, sun&sky, dispersion etc. must be transformed into ACEScg if you plan to use ACES.

Any change this will be in Vray 3.5?

[vlado]

Would this be the correct .ocio file to load into the VFB? https://github.com/imageworks/OpenCo...ter/aces_1.0.1

Yes, it will work fine.

Any change this will be in Vray 3.5?

No, as 3.5 is already out. Hopefully for 3.6

Best regards,
Vlado

[sharktacos]

light color temperature, sun&sky, dispersion etc. must be transformed into ACEScg if you plan to use ACES.

This video shows how colors under bright lights react correctly with ACES and incorrectly with sRGB. This is the main reason I'm interested in using it in Vray. When you say things like "light color temperature" wont work properly with OCIO in the VFB, does that mean that the stuff in this video will not work (bright lights reacting correctly with material color)?

[vlado]

I think you are slightly confused as to what ACES is and why it is used... it has nothing to do with how lights interact with your scene.

This videoshows how colors under bright lights react correctly with ACES and incorrectly with sRGB.

That's not entirely correct to say. They react differently, that's true. But unless you work with actual spectra (in which case color space is meaningless) instead of RGB images, there is always going to be some error in the result. The very concept of RGB implies that some spectral information is already lost, and just changing to a different color space will not recover it.

This is the main reason I'm interested in using it in Vray. When you say things like "light color temperature" wont work properly with OCIO in the VFB, does that mean that the stuff in this video will not work (bright lights reacting correctly with material color)?

No, that's not what I said at all. Lights will work just fine no matter how bright they are. However when you specify the light color as a blackbody temperature value, it is necessary to know the wavelengths for the red, green and blue components of the resulting image, so that the blackbody spectrum can be converted correctly.

Best regards,
Vlado

[sharktacos]

Okay, would it be correct to say that colors under bright lights with ACES react in a way that is closer to how a camera reacts? What I am ultimately interested in is avoiding the problem of an artist setting the lights too dim in order to avoid clipping in the whites, and instead emulating more what a camera does. I was hoping ACES might help with that, at least in regard to what colors do when they get overexposed.

[vlado]

Okay, would it be correct to say that colors under bright lights with ACES react in a way that is closer to how a camera reacts?

No.

What I am ultimately interested in is avoiding the problem of an artist setting the lights too dim in order to avoid clipping in the whites, and instead emulating more what a camera does.

It doesn't sound like you need what a real world camera does. I don't know where this misconception comes from, that real-world cameras are somehow perfect, with no burnouts whatsoever and you can point them at any scene with any exposure and always get a perfect result. This is just not true.

I was hoping ACES might help with that, at least in regard to what colors do when they get overexposed.

ACES will most definitely not help you with that. See my reply here for a discussion of this topic:
http://forums.chaosgroup.com/showthr...495#post728495

Best regards,
Vlado

[sharktacos]

Hi Vlado,

I think we may be talking past each other here. In the post you link to you discuss tonemapping and lights getting blownout (or burnout as you call it). That's not what I am referring to. After all, the Animal Logic renders do get burnout in the video. The point made in the video is about how the colorspace affects what the material colors do when the lights get really bright. I don't expect ACES to have any effect on lights getting burnout. I do expect the colors to respond differently when the lights get bright, as shown in the video.

[vlado]

Lights just emit light. They don't "respond" to anything.

You did mention that your artists specifically make lights dimmer in order to prevent burnouts?

Best regards,
Vlado

[sharktacos]

You did mention that your artists specifically make lights dimmer in order to prevent burnouts?

Yes, but that is not because of the color space. The colorspace would only affect how it looks as it blows out (the color), but not whether it blows out (which it will, and should). Lights don't respond to anything, but material color responds to light.

[vlado]

Using ACES will simply move the problem from one set of colors to another. It will not remove it completely.

Best regards,
Vlado

[sharktacos]

Using ACES will simply move the problem from one set of colors to another. It will not remove it completely.

Best regards,
Vlado

To clarify, when you say "the problem" are you referring to burnout or something else?