Author Topic: dubcats secret little hideout  (Read 109911 times)

2018-07-06, 17:08:48
Reply #210

Juraj Talcik

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correct me if Im wrong but „Diffuse” in corona mat describes total reflectance (diff + direct). when you add „Reflection” on top of that Corona dimms diffuse part to balance the energy.

No, the Diffuse in CoronaMTL is only the diffuse albedo part, not total albedo (Diffuse reflection albedo+ Specular reflection albedo). Second part is correct about Energy Preservation.

But energy preservation in shader doesn't account for scanned F0 values. There is some arbitrary deduction from early version ( two years ago ?) done on diffuse but this is done on top and it's just hack.
It does basically the same thing, reducing the diffuse albedo slightly even before specular is applied. The amount is smaller than 4perc. though.

Same goes for using photometric stereo scanned textures. Energy preservation will only kick afterwards but for the shader to recreate exact albedo you need to feed the diffuse slot only pure 100perc. diffuse albedo.
( additional cross-polarization scan to extract specular scan and then the classic 50perc. negation to get pure diffuse albedo).
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2018-07-06, 18:24:00
Reply #211

piotrus3333

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all clear, thank you.

2018-07-08, 02:22:05
Reply #212

dubcat

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what about doing it with composite map from max? (attached). 13% gray map and color sample on top in "color" blend mode plus maybe lowering saturation a bit in some cases (oversaturated samples made looking nice on screens)
Hey man!

I've tried to do this procedure in RGB, but it's just not possible. Paint companies just love to boost those dark colors in their previews, and keep the bright colors somewhat correct to the LRV.
My workflow is to calibrate as much as I can to a color checker, and use real world light values. This gives me a dull and boring raw render with bright burning light spots. My post settings give these ugly raw renders the "larger than life" feeling. This is just my workflow though, I'm not hating on people who like to get good results with raw renders.

The reason I use 1 filmic HC in my ACES VFB hack is because filmic make our max white 255 RGB. We exploit this with our standard Corona HC setting, and reduce it bellow 1. This will boost our whites and give us that nice pop.

Juraj and karnak has been nice and answered all the 4% IOR questions :)
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2018-07-12, 04:51:24
Reply #213

dubcat

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At some point in your archviz career, someone will request a cross fit machine in their render. I had this terrible experience back in 2014.
The elephant in the room is the hybrid metallic paint. How do you deal with it ?

The reason I want to mention this, is because I had to relive my 2014 nightmare a couple of weeks ago. We could counter this problem with metalness workflow. Chaosgroup has already implemented this workflow in Vray Next.

In our current situation you want to make a material like this. This could be done in one map if we had metalness, and we could discard the falloff map.





edit:

The kind of noise you want to use.



Red is plastic and green is metallic

« Last Edit: 2018-07-12, 19:46:49 by dubcat »
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2018-07-12, 09:38:40
Reply #214

IsmaeL

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Interesting material. Looks very nice.
I thought it's just paint with a higher IOR but never had to make this one before so my opinion doesn't count XD

What does  the metalness map look like. I seams just white.
Falling in love with Corona

2018-07-12, 19:48:26
Reply #215

dubcat

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What does  the metalness map look like. I seams just white.

Hey man
Updated the post with noise samples.
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2018-07-13, 14:05:29
Reply #216

maru

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You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?

2018-07-13, 14:24:15
Reply #217

Jpjapers

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Could you show an example of the material youre recreating?

2018-07-13, 14:29:21
Reply #218

Fluss

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You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?
Yes, I would have done it that way. I don't really like the pure metalness workflow tbh, metallic IOR is not exposed and that's a no-go for me. I just hate the Hardcoded stuff!

2018-07-13, 19:47:30
Reply #219

Njen

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You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?

As long as you are able to treat the dielectric and metallic surfaces differently with the same mask in regards to reflection and diffuse colour it is theoretically possible. But it's just easier to do it with two materials because there would be less nodes to use (less mixes).
Please support my Kickstarter for my animated film, Cyan Eyed (rendered in Corona)!

2018-07-13, 20:23:46
Reply #220

dubcat

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You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?

Hey!

Everything is possible with enough maps.
In this case we have metal flake bits that range from fully covered in paint to not covered at all.
It was easier to control the paint coverage by blending the materials together with random noise values.

Could you show an example of the material youre recreating?

Hey!

It's this type of paint.
If you cross polarize the material, you will notice white spots (metal) in the specular map.
I made the noise size larger in the preview material to make the effect more noticeable.




I don't really like the pure metalness workflow

Hey!

I don't like pure metalness workflow either.
Vray has a really nice implementation. Metalness is 0 by default, no one will notice it's there.
But if we need it, we can change it to 1. Win win.



As long as you are able to treat the dielectric and metallic surfaces differently with the same mask in regards to reflection and diffuse colour it is theoretically possible. But it's just easier to do it with two materials because there would be less nodes to use (less mixes).

Right on!
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2018-07-14, 15:34:34
Reply #221

dubcat

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Here's the first public "Roughness to IOR" LUT test.

Since slate and LUTs are a complete gamma mess, I have embedded all the gamma conversion stuff inside the LUT.

How to:
01. Open the roughness map in Photoshop.
02. Run my high pass action script. This script uses "Apply Image" to generate a perfect 1:1 High pass. It does not use the terrible Photoshop radius based High pass.
03. Load the map inside 3dsMax with "Auto Gamma".
04. Plug the map into "Corona Color Correct" and load the LUT.
05. Plug "Corona Color Correct" into "Fresnel IOR".



Examples, best enjoyed in a new tab.





I have made a High pass filter inside Corona, when I get around to code the new Bridge scripts, you won't even have to deal with Photoshop. In an ideal situation we would get a high pass Corona map, since it's a must when it comes to scanned textures.
« Last Edit: 2018-07-15, 03:55:20 by dubcat »
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2018-07-16, 04:03:41
Reply #222

Basshunter

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Here's the first public "Roughness to IOR" LUT test.

Hi Dubcat,

will you add this info to the Wiki site? It'd be easier to understand for people who haven't followed this from the beginning (Me included)

Thanks for all your knowledge.
« Last Edit: 2018-07-16, 05:26:24 by Basshunter »

2018-07-16, 10:20:31
Reply #223

Jpjapers

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Quote
Hey!

It's this type of paint.
If you cross polarize the material, you will notice white spots (metal) in the specular map.
I made the noise size larger in the preview material to make the effect more noticeable.




Ah right that kind of plastic dipped metal stuff?

2018-07-21, 22:31:04
Reply #224

dubcat

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will you add this info to the Wiki site? It'd be easier to understand for people who haven't followed this from the beginning (Me included)
Of course, I will add it to my todo list :)

Ah right that kind of plastic dipped metal stuff?
Yes something like that :)

------------------------------------

I will be dumping Camera Profiles until the sun comes up today.
Here is a dump of Phase One - IQ3 100MP it "only" cost 50 000$.
I would recommend that you use "Filmic Highlights" 1 as a starting point when using Camera Profile dumps. And then season to taste, because "Filmic Highlights" at 1 will remove everything called highlight. So either reduce "Filmic Highlights" OR if you want to boost the highlights a little, reduce "Highlight Compress" bellow 1, but this will also add contrast. Keep that in mind.

OR everyone could request ACES with at least five parameters:
Slope           - Controls the overall curvature strength.
Toe              - Controls the bottom half of the curve.
Shoulder      - Controls the top half of the curve.
Black Clip     - Moves the left anchor point below 0.
White Clip    - Moves the right anchor point above 1.

But stuff like this only exist in my dreams and Unreal 4.

edit:
So I have dumped a few cameras now, ranging from expensive mobiles, "cheap" cameras to expensive cameras.
Mobiles and "cheap" cameras have a tendency to crunch blacks and boost saturation. While expensive cameras tend to desaturate a little and keep the black crunch to a minimum.
All the devices boost mid/high, and in most cases the center point of the curve is shifted to the left (What Camera Raw 9.9 2010 has been doing all along). 32bit support has been dismissed by Adobe, so RIP 32bit Camera Raw. GG Adobe!

------------------------------------

Waiting for the 18% grey paint to dry.

« Last Edit: 2018-07-22, 02:51:20 by dubcat »
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