Help Topic: OCIO and LUT

[sharktacos]

I think it's worth mentioning that there are several different types of Reinhard tonemapping.

I come to V-Ray from modo where we had Reinhard tonemapping based on this paper: https://www.cs.utah.edu/~reinhard/cdrom/

This tonemaps based on pixel luminance which results in saturated colors (as seen in your image above). User's complained about it and we got an option to tonemap based on RGB values. This results in a "saturation to white/grey" instead. Your image loses some contrast but that can easily be added back.

As far as I can tell, V-Ray's VFB "Highlight burn" uses Reinhard tonemapping on RGB values (it matches modo Reinhard RGB tonemapper), so doesn't have the saturation problem mentioned above

Thanks for clarifying that 1Funk. I wonder if the above Reinhard image is equivalent to Vray's "HSV exponential" color mapping, as opposed to its "exponential" color mapping?

[stevejjd]

I feel that I represent the simple minded artist....I'm glad there has been a huge conversation here about some cool topics .

But being simple minded may I ask all of you what approach should I use that will be consistent and good looking for look dev?

- Should I use Filmic Tone Mapping?
- OCIO >spi-vfx
- OCIO > spi-anim

Can you make a recommendation regarding a lookdev pipeline from 3ds max + VRay to Nuke and Photoshop?

OCIO > spi-anim looks really nice. I also like the filmic tone mapping one.

Also how do I set up Nuke to be exactly like the VFB?



Thanks

[squintnic]

much easier to render linear and do this in post
must be an arh viz thing. people wanting presets and less flexiblity perhaps?

[stevejjd]

This is using LW and with an OCIO profile

[sharktacos]

what approach should I use that will be consistent and good looking for look dev?

- Should I use Filmic Tone Mapping?
- OCIO >spi-vfx
- OCIO > spi-anim

LOL, that's like asking "what camera should I use to shoot my movie?" or “What is the best renderer to use to do good work?” (of course the answer to the last question would be “Obviously everyone knows it’s Vray!”)
In the end the answer is that you want a LUT that emulates the look of your film. In a VFX pipeline, you would therefore get a LUT from DI that emulated the final output of the film and CG artists would use this as a view transform in the VFB. The LUT would thus be created in a program like Resolve or Nuke, and not in the VFB.


Specifically with SPI-animation the intent is not to define the color space for integration of CG with film (a VFX pipeline), but rather to create a 100% cg animation. Here the goal is to have virtual color transforms inspired by real-world film counterparts, but with idealized simplifications that do not delve into the colorimetric peculiarities inherent to physical imaging workflows.
I'm sure there is much more to it than this, but one aspect of this in spi-animation is that it uses an s-shaped transform, rather than a 2.2 gamma curve. This s-shaped curve better emulates how film looks (as illustrated in my earlier post).

[stevejjd]

LOL, that's like asking "what camera should I use to shoot my movie?"

Ahahahaha

Well come on! lets have a massive conversation about why we have a preference for a look

Just like a conversation about this Canon Vs Nikon. Let us discuss the top 2 OCIO profiles that look beautiful by default. What are the pro and con of each

We dont always have to talk about 1+1 all the time. Lets us talk about why we would prefer Filmic tone mapping or the Sony OCIO profiles. Let us compare which one we like best in Nuke.

I know Vlado loves to talk aesthetics ;D

p.s....and yes V-Ray is the best!

[iancamarillo]

something like the false color lut might be useful in the VFB

[chadstevens]

something like the false color lut might be useful in the VFB

There is already something similar in Vray's VFB, it's the little icon at the bottom left that says force color clamping.

[vlado]

There is also a button that shows colors specifically above 1.0 and below 0.0.

Best regards,
Vlado

[stevesideas]

Not sure if anyone has posted this already but there is a plugin for aftereffects to load in these profiles: http://fnordware.blogspot.co.uk/2012...r-effects.html

[stevesideas]

Vlado, do you know if/when the ability to save out OCIO profiled images might occur ?

I'm trying to use Fusion to apply the filmic profiles but I only seem to get one option, not the 6 or so that are available when using vray.

[stevesideas]

Fusion tools: http://www.racoon-artworks.de/?p=597

[OPEN_RANGE]

i have followed this thread with much interest. I have a rendering I save as .exr (16bit). I load the Filmic High Contrast.cube (from filmic.zip file in this thread) to the LUT in the VFB. Looks good.

Now I want to apply it to the file in pshop. that's what I can't seem to get correct. I open the.exr in pshop and use Image>Adjust>Color Lookup to apply the Filmic High Contrast.cube. It whacks out the gamma of the image and I can't seem to correct for it. Makes it look way to dark and contrast. similar to what it looks like if turning off the sRGB button in the VFB.

Can anyone advise as to how to get the filmic applied to the exr once it's in pshop?

[stevejjd]

Resource Link

- PSD manager will export your frame buffer and passes to Photoshop in the correct order and with the correct blending mode as well as baking all color grade info to an adjustment layer (would be interesting to see if it bakes the OCIO as well)

How to look at RAW DATA

I used to argue that V-Ray should show the final desired look in the buffer but now I have completely changed my mind.

I now realize that you must try and match the desired look closely in the VFB while always being aware that you are looking at RAW DATA.

Just like a professional photographer will treat his or her camera as an instrument that captures the widest gamut of unfiltered data, so to does V-Ray.

When rendering in V-Ray, You must look at the Potential of RAW DATA and not be distracted on the ugliness of RAW imagery.

Establishing a bridge to Nuke/Photoshop early on is a helpful way of understanding the potential and power of RAW 32bit data sets. Beauty treatment is best done in post with dedicated retouching tools like Nuke & Photoshop. The current VFB color grading tools are more than enough to preview the render in a more natural way. (I like Filmic tone mapper)

Steve ~

[sharktacos]

So I thought I'd share this. First we have an image viewed with the usual sRGB gamma (in the VFB):



Next we have the same image viewed instead with spi-anim color transform:



Note that we get the nice "shoulder and toe" of a photo here because it applies an s-shaped curve similar to a camera, rather than just doing a simple gamma shift on it. Notice also the lamp shade is not blown out in this image. This is not the same as tone mapping where the white levels are brought down. It is still possible to have the image blow out if it gets bright enough, just as it is possible to do that with a camera. However, the color transform makes that happen more the way ot would with a camera so you have less of a problem with colors blowing out when you don't want them to -- which is a problem that happens a lot with renders (because of the sRGB transform) and not with cameras.

I also want to stress that, just as one cannot set up the lights without a linear workflow and then switch to a linear workflow and expect those lights to look good, one equally cannot simply apply spi-anim (or filmic or whatever view transform you want to use) to the render later in post. One needs to view the render with this color transform as the lights are being set.

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