Author Topic: dubcats secret little hideout  (Read 129181 times)

2018-07-06, 03:52:02
Reply #195

arqrenderz

  • Active Users
  • **
  • Posts: 727
  • arqrenderz.com
    • View Profile
    • arqrenderz
Just WOW to the last dubcat post, you know a lot of this.
Where can u normal user start, in order to better understand all this concepts?

2018-07-06, 11:11:55
Reply #196

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
finally. thx for educating people about flares on hdris.
another thanks for all of you guys chasing fstorms tone mapping. great work. I'm spending more and more time on this forum because of content like that.

quick question about paint color samples: why subtract 4% form 13% LRV when corona's mat does energy conservation for you?
and 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)

2018-07-06, 11:34:41
Reply #197

johan belmans

  • Primary Certified Instructor
  • Active Users
  • ***
  • Posts: 728
    • View Profile
    • belly.be

2018-07-06, 12:36:51
Reply #198

Juraj Talcik

  • Active Users
  • **
  • Posts: 4050
    • View Profile
    • studio website
quick question about paint color samples: why subtract 4% form 13% LRV when corona's mat does energy conservation for you?

I have found this to be very arbitrary ad-hoc introduced in Corona shader. It was done long time ago as quick-fix for people over-doing bright albedo.
It's not part of the energy conservation model but additional part on top. Perhaps the devs could show what exactly it does because I haven't found it to correlate with 4perc (the most common base reflectance of insulator).
talcikdemovicova.com  Website and blog
be.net/jurajtalcik   Our studio Behance portfolio
Instagram   Our studio Instagram, managed by Veronika

2018-07-06, 13:12:56
Reply #199

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
4% or 24% does not matter as long as diffused reflections are dimmed by direct ones. that looks ok to me in Corona but I also never bothered with side-by-sides.

2018-07-06, 15:04:08
Reply #200

karnak

  • Primary Certified Instructor
  • Active Users
  • ***
  • Posts: 65
    • View Profile
Let's say that the color was sampled with a spectrophotometer. What you get from that instrument is one reflectance value that contains both diffuse and reflection (with no distinction). So, if you want only the diffuse you have to know the reflection value and subtract it from the value the instrument gave you.

When you read that you have to subtract 4%, it's because they assume the color was sampled from a non-metal surface with the default 1.52 IOR (that at normal incidence equals 4%).
Corona Academy (May 2017)

2018-07-06, 15:29:08
Reply #201

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
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.

2018-07-06, 15:40:22
Reply #202

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
...dimms „Diffuse” part to balance the energy.

2018-07-06, 17:08:48
Reply #203

Juraj Talcik

  • Active Users
  • **
  • Posts: 4050
    • View Profile
    • studio website
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).
talcikdemovicova.com  Website and blog
be.net/jurajtalcik   Our studio Behance portfolio
Instagram   Our studio Instagram, managed by Veronika

2018-07-06, 18:24:00
Reply #204

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
all clear, thank you.

2018-07-08, 02:22:05
Reply #205

dubcat

  • Active Users
  • **
  • Posts: 423
  • ฅ^•ﻌ•^ฅ meow
    • View Profile
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 :)
             ___
    _] [__|OO|
   (____|___|     https://www.twitch.tv/dubca7 / https://soundcloud.com/dubca7 ( ͡° ͜ʖ ͡°)

2018-07-12, 04:51:24
Reply #206

dubcat

  • Active Users
  • **
  • Posts: 423
  • ฅ^•ﻌ•^ฅ meow
    • View Profile
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 »
             ___
    _] [__|OO|
   (____|___|     https://www.twitch.tv/dubca7 / https://soundcloud.com/dubca7 ( ͡° ͜ʖ ͡°)

2018-07-12, 09:38:40
Reply #207

IsmaeL

  • Active Users
  • **
  • Posts: 47
    • View Profile
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 #208

dubcat

  • Active Users
  • **
  • Posts: 423
  • ฅ^•ﻌ•^ฅ meow
    • View Profile
What does  the metalness map look like. I seams just white.

Hey man
Updated the post with noise samples.
             ___
    _] [__|OO|
   (____|___|     https://www.twitch.tv/dubca7 / https://soundcloud.com/dubca7 ( ͡° ͜ʖ ͡°)

2018-07-13, 14:05:29
Reply #209

maru

  • Corona Team
  • Active Users
  • ****
  • Posts: 9807
  • Marcin
    • View Profile
You can map Fresnel IOR so wouldn't it be possible to make this with just a single material?