Linier workflow and getting the VFB to match my ICC diffuse colour inputs.

[LewisJT]

Hi Guys,

I'm having a little trouble with Vray’s linier workflow and getting the VFB to match my diffuse colour inputs.

My aim is to create a physically correct rendering studio with output and VFB matching the ICC input from creative suite and a similar system for internal colour creation.

I have broken the problem down into two areas:

1. External Embedded ICC Textures
2. Internal VrayColour map

ALL Examples shown in Vray 3.5 beta, however problem existing in regular 3.5 & RT


1. External Embedded ICC Textures

Fig_01. I create my swatch texture in a creative suite package and export with an embedded ICC sRGB iec61966-2.1, then assign my texture through a HDRi map. Set Colour space to sRGB, and Render.

Results
• RGB Beauty pass: Match input = NO Fig_04a Fig_04b
• Diffuse channel pass: Match input = YES Fig_05a Fig_05b

Q: Why does the beauty pass not match the input values? I have tried with Check “display colours in sRGB space” on and off with no difference?



1. Internal VrayColour map

Second is the creation of accurate colours inside the material editor. I’m wanting to create an 11 step tonal system of greys spheres to match the colour swatch card.

We use a VrayColour map assigned to the Diffuse channel and then choose our RGB values as we want them as taught at SOA. In this instance. I have Isolated Sphere Grey217 (input 0, 0, 217) and scaled up for this example.

• RGB Beauty pass: Match input = NO Fig_06a Fig_06b
• Diffuse channel pass: Match input = NO Fig_07a Fig_07b

Q: Here no passes match the input of the VrayColour, RGB or Diffuse? You can also see in diffuse pass the sphere doesn’t match the correct HDRi swatch.


Conclusion:

The two above points have left me confused as I was under the impression that checking “Show colours in sRGB space” would show VFB renders as they will be when opened in PS and the sRGB curve is reapplied?

I understand the linier workflow principle as taught my Gian Piero at SOA (The masterclass is an awesome course by the way and huge respect to those guys)

• Input all diffuse textures with ICC sRGB applied
• 3DsMax linearizes the textures for the render engine
• VFB: Check “display colours in sRGB space” to de-linearize results to view how you will view in post-production.
• Vray calculates the textures linier in the background
• SAVE: Max outputs images with the sRGB gamma reapplied (except in floating file formats)
• https://renderman.pixar.com/view/LinearWorkflow


Once again my aim is to create a physically correct rendering studio with output and VFB matching the ICC input from creative suite and a similar system for internal colour creation. Just as you would work in a real life photography studio.


1. Extra question

This is a workflow question which maybe solved with the above solution.

Before attending SOA and learning Liner workflow, I would input diffuse textures with a regular Bitmap and crop branded swatch textures using the crop function. A highly useful workflow in many ways as we could quickly update scenes with branded colours by simply updating the swatch texture and manipulate the crop function.

However to work with the Linier Workflow I moved over to using the HDRi however in doing so we lost the “visual” crop function which we are missing desperately

Q: Is there anyway of using a workflow where I can keep the functioning LW and still have the “visual” cropping function?


I understand this is a long opening however I hope I have been succinct in expressing the problem. I can supply a supporting Max Archive file in 2015 & 2017 should you wish to investigate.

Huge thanks in advance, I look forward to hearing your response.

Kind regards

Lewis

[LewisJT]

As promised, Archive zip file_2015-17

Hi Guys,

Zip file containing max2017 Archive zip folder with a back save of 2015 included.

Any questions or other requests please don't hesitate to contact me.

L

[Morne]

The HDRI workflow is cool and all, but the way you were doing is fine also.

9 out of 10 times the issues you're having with no match between a render and what you see in photoshop is down to a monitor profile loaded.

If you either
A) Calibrated your monitor
or
B) Loaded the software or drivers that came with your monitor

...then you have to load that same profile into the ICC slot in the VFB and like magic things will match (because Max doesnt read any profiles and defaults to sRGB, but V-Ray is smarter and it can use whatever profile you tell it to)
You can just make a copy of the monitor profile and rename the extension from icm to icc and load it into the VFB

[LewisJT]

Hi Morne,

I'm running two dell ultra-sharp monitors Dell U2713H & Dell U2711.

Neither have been calibrated with an external reader. I have the preset modes on the monitor (hardware) set to Adobe RGB as I was under the impression this showed the largest range of colors?


The monitors were default to Dell so I changed them to ICC sRGB
No change to the rendering results...

However

I checked the ICC profile and the rendering went dark, when I checked it back off the colours still stayed dark?


Now the spheres reference correct however the textures are now all very dark. I double check the textires with a regular bitmap and render is still dark?

[Morne]

Just checking and unchecking that does nothing. Just a bit to the right of that, click that dropdown arrow. You're suppose to load an actual icc file in there.
There's a bug in the VFB when you untick ICC, it doesn't switch back to sRGB, but shows you linear colors (which are darker)
In the middle bottom of the VFB there's a button that either says sRGB, or ICC. When you click and hold it, you can switch between the 2. The button must be "IN" all the time. Either on sRGB or ICC
Don't use the monitor's in built profiles such as AdobeRGB, especialy if everywhere else you're aming for sRGB.

Anyway, your issue seems to be something different since the monitor profiles are set (software) to sRGB in which case you can just use the sRGB button in VFB and ignore ICC

[LewisJT]

Thanks,

Yes I can now see the VFB if you hold the button a flyout appears, very small and easily missed. I updated the software in window to carry the ICCsRGB prfiles. Origionall they were set to the dell high Gamut profiles.

Seems i fixed the problem, I hadn't apply the 2.2 gamma in the VrayColour, once i did't I know have the correct output.

I've also been speaking with a friend and he mention because vray & Max render in sRGB having a high Gamut monitor has no advantages. Which is a shame.

I was hoping to create a high Gamut workflow from Creative suite to max/vray/corona back to creative suite then out to Print/digital

[Morne]

OK Had a chance to look at your images and max file finally. Only issue here is you're using the VRayColor incorrectly. When specifying an RGB value in the VRayColor, you've set it to 2.2 but left the "gamma correction" to NONE.
You can then set the gamma to whatever value you want, it wont affect the RGB you entered. You have to change the gamma correction to "SPECIFY" then the value to 0.4545 to get an inverse gamma. Then your image and VRayColor will match in the diffuse.

I've also been speaking with a friend and he mention because vray & Max render in sRGB having a high Gamut monitor has no advantages. Which is a shame.

...which is why you load the calibrated ICC into the VFB with VRay to "bypass" the sRGB limitation so to speak


EDIT: I also need to add if you want to go through all this trouble to work "correctly", but dont have calibrated monitors, you're mostly wasting your time. Get yourself a Xrite ColorMunki and calibrate those displays!

[LewisJT]

So if i calibrate the monitors, and feed the profile into vray and Photoshop/creative suite i will have a high gamut workflow..?

[crazy homeless guy]

physically correct rendering

This does not exist. Anywhere. In any studio. Everything is a subjective approximation of reality.

[joconnell]

Adobe rgb might be a high gamut colour space and have saturation that isn't totally helpful for video work - might be safer on regular srgb unless you're in print land.

[LewisJT]

Cheers guys.

Great responce, good to know about adobeRGB and video issues.

Huge thanks for all the support.

Hope the issues and insights uncovered can help others down the line who see this thread.

Thanks again.

L

[LewisJT]

I Guys,

Following the feedback here I updated my testing scene & encounter issues when reaching darker grey.



So I did a further small test to see if the issue was coming from the scene and I encounter 2 issues.

1. Vray colour isn’t reproducing like for like values as per the HDRi map especially at lower grey values.

2. When you update one VrayColour with Gamma Correction i.e. Specify 0.4545, then all VrayColour update in the material editor automatically.

The material update maybe to ensure consistency. I was trying a comparison between correction and no correction and the results showed no difference

Any info is greatly appreciated.

[Morne]

HDRi is basicaly a linear format using floating point values. When you compare, check the floating point, not the 8bitRGB

To that effect, change your source file from a jpg or whatever it is, to an actual 32bit HDRI and do the test again.

In ps, make a new 8bit image and paint it 4,4,4. In PS change the image > mode > 32bit.
Now still in PS, grab your eye dropper and pick that 4,4,4 you just made. the rgb will be 0 (or 0.001 float)

float values from 0 to 1 is basically RGB 0 to 255. Floating point above 1, is in laymen's terms above 255 in rgb

[LewisJT]

Thank Morne,

I'm happy with the test card. Its the lower value vrayColour applied to the spheres that's isn't sampling as per the input values.

Apologies, I should have shown the spheres in front of the test card clearer.

If you notice on the larger screen grab, ( vray_colour_2.2 copy.jpeg )the upper samples shown are coming from the spheres in front of the test card. ( see the camera viewport ) These spheres have the vrayColour applied to them.

For example the input value 8,8,8 vraycolour sphere reads 1,1,1 in the diffuse? I'm loosing colour information somewhere.

[Morne]

Will test when render done...