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Vray Camera Setup
show user profile  9krausec
Morning folks. Question about the Vray physical camera setup for you...

I'm trying to make sure that the value of the colors used (with correct gamma applied to them) are correct... It's a bit of a challenge considering so much of Vray is relative to what is going on in your scene (you could have your camera setup with a 10,000 shutter speed look acceptable as long as your lights are intense enough to compensate).

So.. Is there any issue you guys can see with pumping a gamma corrected swatch into the environment color (which changes with camera settings) and base you camera setup on the colors picked up form the environment? This would allow you to pick up accurate Value/RGB values void of any shadows, reflections, etc...

I'm thinking about using this as a basis to set my camera. I just wanted to ask the community to doubly be sure that this was an okay thing to do.

Edit: Setting up the environment like that yields the same result as setting up a vray light material with an intensity of 1.0 with a gamma corrected color swatch in it.

After messing around I was able to hone in on camera settings that would give me accurate diffuse color reading. Only catch is that in order to do this I had to switch the "corrected colors" checkbox on in the pixel info reader of the VFB (show below)-

I'm assuming this box corrects the color readings to take into account LWF and sRGB space? If so this is a nice step in the right direction.

- Portfolio-

read 934 times
12/8/2015 5:52:20 PM (last edit: 12/8/2015 6:37:08 PM)
show user profile  Bolteon
More of a question for the Vray forums. Those are some specific details right there...

-Marko Mandaric

read 919 times
12/8/2015 7:34:29 PM (last edit: 12/8/2015 7:34:29 PM)
show user profile  9krausec
K, I'll post there. I just figured someone here might know.

It all comes back down to color accuracy. I need to be certain that if I create a gamma correct swatch for diffuse it's going to come out correctly (without having to double check every time I render something out).

In the mean time, if anyone does know here, feel free to post up. Other than that I'll go to the Vray forum.

- Portfolio-

read 917 times
12/8/2015 7:40:37 PM (last edit: 12/8/2015 7:40:37 PM)
show user profile  donvella
Theres a few steps to this setup and ill do my best to explain how we come up with this workflow - let me know if you need clarification on anything.

I work with real estate photographers and retouchers, so consistent and accurate lighting/camera setup is crucial to our workflow.

I found the easiest way to handle gamma in max is to turn the LUT off.

Reason being - it keeps everything input in max at 1.0 and output @ 1.0 and then you apply the 2.2 curve at the very end (sRGB button in the VFB). Saving as .exr also preserves this - so it will display automatically as 2.2 in post. The dual benefit is you can import anything from any scene with whatever gamma applied and it will correct this to a 1.0 input - thus any asset you merge into your scene will appear correctly as the jpg does 1:1

The next step is to tell Vray to do the same through color mapping

You will hear a lot of people scream about the 'linear workflow' button, ignore this for a moment. This simply keeps everything at 1.0 until you apply a sRGB curve.

Lets put into our Environment a HDRI. You can use a plain color - I prefer to use a HDRI because it mimics real world ambient lighting.

I am using \VizPeople HDRI - Vol2\HDR_12k\vp_HDRi_v2_08.hdr
Be aware, this is the only component you need to alter (overall mult: 1-10) depending on the intenisty of the image being used. Ill explain why in a moment. You will notice I have turned the RGB output to : Intensity as grey instead of default RGB color. This is because I dont want it to introduce any color - only for ambient.

You can now adjust your camera to a real world setting such as

Note: I spend alot of time trying to mimic 'real world camera settings' when in fact, after being on a photoshoot with a photographer I realised how little this actually really mattered - as they just shoot the photo and adjust the exposure generally after as it contains raw lighting and is the retouchers job. This is only really for consistency in max.

If you have this setup - you can now basically apply a Dulux Swatch to a plane and render it and it should be basically almost exact. The only difference being because im using a HDRI you may get some slight variation (slight). Example

Dulux Swatch - Army Issue

Render from camera top down

Ofcourse any lights you add will vary these values. Now to the second part of your question, and something I also strive to perfect. Lighting....

My recommendation is to not use arbitrary values in lights such as Multiplier of 1.0 etc... With your scene setup like this you can now use real world lumen values and they will appear as they do in real life.

In a typical case Ill use a Halogen 100watt bulb with a Kelvin of 3000 (typical halogen). To keep it simple you only need to know the range of standard lights

40watt - 450 Lumen
60watt - 800 Lumen
100wat - 1600 Lumen etc...

And the Temperature (Kelvin) range:

2800 - Incandescent
3000 - Halogen
4500 - Natural White etc....

The only thing to note from this is your vray sun will appear extremely bright in this setup (as it uses arbitrary values) so you will need to have it set very low (0.02 - 0.1) depending on your camera shutter. You will understand as you play with this base setup.

I have this saved as my maxstart - so I never need to adjust anything unless I change the HDRI. I try keep it simple because this is what real estate photographers generally do (and it makes my life simple and work consistent for color/light matching). Once you change the HDRI you only need to do a few quick tests on a plane after adjusting the Overall Mult in the Processing section of the HDRI material.

Hope this helps. Let me know if I borked something

read 910 times
12/8/2015 10:33:19 PM (last edit: 12/8/2015 11:02:55 PM)
show user profile  herfst1

You're a chap, Don.
read 904 times
12/8/2015 10:53:18 PM (last edit: 12/8/2015 10:53:18 PM)
show user profile  mike_renouf

I have a setup that works for my requirements but I will definitely try yours Donvella and get an idea if I've fooled myself into thinking mine is good enough!

read 896 times
12/8/2015 11:10:52 PM (last edit: 12/8/2015 11:10:52 PM)
show user profile  donvella
ill put this up on my blog as a tutorial if you guys find it useful. Ill extend this a bit further by showing you my render settings - they are universal for low res and high res (6000px +) and you never have to adjust any subdivisions in the scene for lights, materials or anything else - just plug and play - let the vray engine handle the subdivisions. This is a modified version of Vlado's new vray 3 setup. His setup was good but I needed to tailor it a bit for production speed. (we need 6k renders in 1 hour on a 24core machine). All elements need to be clean as example sample rate below....

edit: his settings actually lock subdivisions completely - you cannot adjust them. Makes life very simple

read 892 times
12/8/2015 11:23:11 PM (last edit: 12/8/2015 11:30:24 PM)
show user profile  Bolteon
Yeah, put this together into a post. Would be worth it.

We used a similar setup in the Microsoft work...

The only thing I would mention is explicitly is that setting the Sun values arbitrarily isn't the right way to go about it.

In real life, if you were shooting with an open sun; you'd use ND filters but there's no current implementation of those in Vray.

Nicely done.

-Marko Mandaric

read 888 times
12/8/2015 11:46:47 PM (last edit: 12/8/2015 11:48:17 PM)
show user profile  9krausec
Thanks donvella for all the information. Will be using this for production.

- Portfolio-

read 883 times
12/9/2015 12:04:10 AM (last edit: 12/9/2015 12:04:10 AM)
show user profile  mike_renouf
From the vray online help files about the linear workflow checkbox:

"Linear workflow - this option is deprecated and will be removed in future versions of V-Ray. When this option is checked V-Ray will automatically apply the inverse of the Gamma correction that you have set in the Gamma field to all VRayMtl materials in your scene. Note: 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."

So basically if you are not applying any gamma correction to bitmaps anyway, checking this box won't do anything? Does that sound right?

read 862 times
12/9/2015 10:18:23 AM (last edit: 12/9/2015 10:18:23 AM)
show user profile  donvella
Glad I could help 9krausec.

The linear workflow checkbox inverts the gamma on render time (.45) on all diffuse maps. The good part is it keeps displacements and bumps at 1.0 so you dont have to manually change them - most people dont really care but it makes a difference because they get a white wash.

The guy who come up with this method originally requested this feature to remain in vray3, ill be doing the same moving forward (or find a new method if it is removed). The other benefit is you can just use a standard color in your diffuse instead of a vray color (which does the same thing .45) but its more work - I prefer simple methods. You will also notice two things when u turn off your LUT - your viewport will appear darker (this is not a bad thing), and your Value range is extended. When you apply a gamma curve to your color swatches it crunches the black values.

I used to use the LUT for years, but I prefer this for simplicity.

From memory (id have to re check this now), it also affects your render elements - such as wirecolor as it uses max standard colors - having this at 1.0 keeps them as you set them 255 red etc. Edit: a secondary benefit to this is instead of using multimattes which only gives you RGB, you can use 255 red + 255 blue - giving you a magenta channel, you can also have yellow etc...

read 856 times
12/9/2015 10:52:42 AM (last edit: 12/9/2015 11:02:39 AM)
show user profile  mike_renouf
Good stuff. I did find it odd looking at the material editor without gamma correction - everything does look really dark, but I suppose I could get used to that if I choose to change to this method.

One of the things I really did like was the note you made about changing the HDRI to greyscale, I hadn't done it that way before. Cheers for the tip.

I've always put the HDRI into a domelight because in that way I can control the subdivs. I suppose that's not necessary for your workflow since you've already said you can ignore those with the universal settings.

read 847 times
12/9/2015 11:39:54 AM (last edit: 12/9/2015 11:39:54 AM)
show user profile  ijzerman
Wow this is a pretty cool thread. Thanks for sharing :)

Pushing buttons since "86
read 843 times
12/9/2015 12:15:19 PM (last edit: 12/9/2015 12:15:19 PM)
show user profile  donvella
I prefer use environment or background for hdri instead of dome because its less noisey. But then u cant have it as a light select. Either or really depends on whos doing post lol

read 842 times
12/9/2015 12:19:51 PM (last edit: 12/9/2015 12:21:06 PM)
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