Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - dubcat

Pages: 1 2 [3] 4 5 ... 29
31
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-08-28, 21:35:13 »
Hey man!

I have an account, downloading right now. Will have a look at it in the coming days together with Mrazkos HDRi question :)

32
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-08-28, 20:58:46 »
For example 03-29_Sunset from noemotion if you wouldn´t mind :) thanks a lot

Hey!

I will have a look at it in the coming days :)

Do you think there's any way to guess the albedo color of an object (In this particular case a wood floor) from just reference photos (Low quality) with different light conditions?

Hey man!

You can compare CGI values to Ohms Law Triangle



When it comes to Ohms Law, you divide volts with amps and ohms. And multiply Amps and Ohms. If you know two of the values, you can calculate the third value.



We don't divide or multiply in my CGI triangle. But if you hold your hand over the unknown value, you can see what values you need to have, to calculate the third value.

I can share a link to that particular asset, if someone is interesting to give a try to this mystery.

Hey!

That would be awesome!

33
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-08-23, 21:37:51 »
The Canon 5D Mark I (classic) always had something special in the color rendition.
Hey!

Here is the RGB version of the LUT. It actually brightens 0 RGB, quite interesting.

Hey Dubcat.

Hey man!
I see oddvisionary has been kind enough to answer when I was afk. I would use your sculpting software of choice and Painter.
I would also generate an IOR map from the normal map, since this model would be fictional and not based on specular scans.
You need the IOR map for micro shadowing like here:



Hi dubcat, I got into hdri calibration thanks to your tips thank you! However I would like to somehow calibrate hdri that has partially overcast sun - is that possible in any way? or is it just eyeballing then? for example some of noemotion evening hdris so that the intensity of direct light would be correct

Hey!
If the sun is blocked by clouds and the HDRi provider does not include a grey card reference, we just have to guess. If you give me a link to one of the HDRis you have in mind, I can take a look at it.

If you are interested in getting real world values, you can do this:

- Go outside when it's cloudy.
- Place a ColorChecker grey card on the ground.
- Take a photo of the grey card.
- Recreate the grey color material. If you use a ColorChecker Passport, the grey bellow yellow is 19.8% linear (122 sRGB). (A grey sphere would be best, since you can capture F0).
- Create a camera with the same settings you used on the real camera.
- Calibrate your HDRi until the real and digital color checker match in values.

Before doing that i want to be sure that i won't do any irreversible damage.

Hey man!





My guess is that the HDRis you tested already had low sun values, that are bellow Photoshops clip value. If you add 7 +20 Exposures in Photoshop above a 255 RGB layer. You will go above the threshold and it turns black.



I've attached the Corona Sun/Sky HDRi saved from Corona, if you want to do tests on that one.

edit: fixed typo, i meant specular not spectacular :p

34
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-08-11, 12:15:13 »
do you have more dumps to test?

Hey!

Do you mean camera luts ?
What cameras would you be interested in ?

edit:
If anyone of you have a camera request, let me know and I'll see what I can do :)

35
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-08-08, 00:20:21 »
Every now and then I get questions about Reflection Level and IOR. I will use this post as a reference.

I associate Reflection Level with Opacity in Photoshop.
Imagine IOR inside a folder in Photoshop. This folder is Reflection Level. Bellow this folder you have a black layer.
The IOR/Black layer will always be 100% opacity. But you can change the Opacity of the Reflection Level folder.



When Reflection Level is 1, the folder inside Photoshop is 100% Opacity. We get 100% correct IOR values.



When Reflection Level is 0, the folder inside Photoshop is 0%. We only see the black layer. 0% IOR values.



If we change Reflection Level to 0.5, the folder inside Photoshop is 50%. We get 50% IOR and 50% black.



So what is 50% IOR.
First we need to convert the IOR value to Reflectivity.
Let's say our material is IOR 1.5.

Reflectivity = (((1-IOR)/(1+IOR))^2)*100 = 4%

Then we take 4% and multiply it by 0.5 (50%) = 2%

Let's convert it back to IOR.
IOR = 1/((2/(sqrt((Reflectivity/100))+1))-1) = 1.33

So if we use IOR 1.5 and 0.5 Reflection Level, our F0 point will be IOR 1.33 instead of 1.5.
But this is not the problem. The problem is that we also reduce the Fresnel edge by 50%. This edge should be pure white (1 float aka 255 RGB).
50% of 1 is 0.5, the Fresnel edge will be 127.5 RGB instead of 255 RGB. This is where our material is no longer physically plausible.

But since we have done the math, you can just change the IOR to 1.33 and increase Reflection Level to 1. This will give you the same result as IOR 1.5 and 0.5 Reflection Level. Only the material will be physically plausible.

When you buy models online, they usually come with ridiculous values like IOR 1.8 and Reflection Level 0.5.
These are not physically plausible, since Reflection Level is bellow 1.
Let's do some math and see what the actual IOR value is.
IOR 1.8 is 8.16 Reflectivity.
50% of 8.16% is 4.08%.
4.08% is IOR 1.51.
In this case they could just have used IOR 1.5 and Reflection Level 1, and the material would look the same and be physically plausible.

We can't touch Reflection Level, but there are two methods you can use to add imperfections to your reflections. (If we ignore bump/normal/displacement).
You have to ask yourself these two questions:
* Are these imperfections surface imperfections ? In that case you want to use a glossiness map.
* Are these imperfections caused by micro occlusion, small scale shadowing. In that case you want to use a custom IOR map to fake depth.
  Corona could auto generate this IOR map from a normal map, but that is currently not the case. (I will share a Normal to IOR LUT soon, but you have to do a few steps before applying the LUT).

If you have a cross specular scan of your material, it does not hurt to use my roughness to IOR LUT. Real world scans always include micro occlusion that Corona can not generate with glossiness or normal maps.

In Vray Next they have added this tool tip. Maybe Corona should do this too.



Here are some examples that show how F0 and the Fresnel edge gets clamped when you reduce Reflection Level.
The right square image is an unwrapped version of the sphere, where each vertical line is a degree. And the right image is a render in Corona.













TLDR;
* Leave Reflection Level at 1 for physically plausible materials.
* Use glossiness for surface imperfections.
* Use IOR maps for micro occlusion, small scale shadowing.

36
[C4D] General Discussion / Re: Fresneloff
« on: 2018-08-07, 08:45:52 »
That workaround has been removed now so there is no difference at all. 999 is the highest you can get.

Please feel free to correct me Dubcat.

Right on!

37
[C4D] General Discussion / Re: Fresneloff
« on: 2018-08-06, 20:27:21 »
They removed support for this fix a few Corona versions ago.
You will get the same frensel taint no matter what you do.


38
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-08-02, 21:51:37 »
Is ACES a color space?

When your media has gone through the IDT process, it will be converted to ACES color space.
ACES color space is greater than the gamut of the human eye, so it's future proof.

39
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-08-02, 21:15:45 »
what about "Filmic Shadows"?

Hey!

We use "Filmic Highlights" 1 because it only affects the highlight.
It does not mess with contrast. Here is a little 0-1 RGB dump, the curve continues like that above 1 float.
I can post some log dump examples of different tone mappers when I get time.



"Filmic Shadows" on the other hand, will only add some wonky contrast to your render.
The camera dump LUTs already contain contrast from the camera. So I would not recommend that you use "Filmic Shadows" in combination with the camera LUTs.



1) Do your LUTs (Like Canon 5DS .cube file) work in other render engines like V-Ray and FStorm or just Corona?
Hey!

They work in any engine that applies LUTs as sRGB. Corona and VFB+ are the only programs I know that extrapolate values above 1 float.
If you look at the sun and apply a normal LUT in Corona, the sun values are still correct. If you apply the same LUT in Vray, fStorm or Photoshop, the sun value will become 1 float or 255 RGB.


2) Would you kindly help me understand what ACES is? No matter how hard I try, I can't make sense of it!

ACES stands for "Academy Color Encoding System". ACES help unify different encoded material through a prosses called IDT.

But in this thread I'm only talking about the post production tools.
You can see and play around with the tonemapper here

https://www.desmos.com/calculator/h8rbdpawxj

4  Slope        - Controls the overall curvature strength.
7  Toe           - Controls the bottom half of the curve.
11 Shoulder   - Controls the top half of the curve.
8  Black Clip   - Moves the left anchor point below 0.
12 White Clip  - Moves the right anchor point above 1.

and of course the color space:



fStorm is the only engine I know that has ACES color space.

40
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-08-02, 01:08:43 »
I dumped the iPhone 10.6 Telephoto Camera just for luls.
It has pretty soft darks and crunchy brights, not bad at all.
"Filmic Highlights" 1 should give you a nice start compared to ACES.

It's still RGB dump, haven't had time to fix my HSL/HSV dumper.

41
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-07-28, 00:54:33 »
What is your background?
Half Life 1 modder turned Archviz / BIM :)
My first introduction to 3dsMax was Autodesk Gmax, because Milkshape 3D was lacking a lot of features.

from adobe page
Quote
In Photoshop, the luminance values of an HDR image are stored using a floating-point numeric representation that’s 32 bits long (32‑bits-per-channel). The luminance values in an HDR image are directly related to the amount of light in a scene.

I've posted examples all over the forums for years, but I guess it's best I recap everything here.

I'm running the latest version.



#1
If you go back a few pages and download my ACES tonemapper script for Photoshop. You will notice that bright lights becomes black pixels. This is because Photoshop does not calculate negative values.
The script will split your render into two images and then divide those images together. Photoshop does not handle negative math well, and will return black pixels.

#2

Corona Sun



Corona Sun rendered as HDRi and re-saved in Photoshop as EXR.
Goodbye values.



Corona Sun rendered as HDRi and re-saved in Photoshop as HDR.
Better than EXR, still not what we expect.



#3

32bit floating point displacement.

Proper 32bit map rendered in Corona



Re-saved in Photoshop as EXR.
Since this map does not exceed 20 Photoshop Intensity, it will not clip.
Negative values work as intended also.



Re-saved in Photoshop as HDR.
Since this map does not exceed 20 Photoshop Intensity, it will not clip.
But since it's HDR, it will not have negative values.
It also has some weird ass shadow artifacts.



So if you use Photoshop you are left with these choices:

EXR: Clamped bright values and clamped negative values.
HDR: Somewhat proper bright values and no negative values.
Internal: Can't do negative math.

I bugged Adobe back in 2016 about this problem. They said they didn't understand what I meant about clipped values above +20 RGB, and asked me to take a print screen of the problem. (I had provided renders like the ones I posted here, but they wanted a print screen of the HDR image) That is when I gave up.

42
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-07-26, 19:28:39 »
Hey!

Quote from: johnymrazko
Are you using native 3ds max maps for a reason? would this work with Corona Mix and Corona Bitmap in the same way?
You could use CoronaMix and disable "Perform mixing in sRGB space".
I usually drag and drop bitmaps into slate, and then run Corona Converter to convert them to Corona Bitmap.

Quote from: johnymrazko
when creating mask in photoshop, can I just add a new layer on the hdri and create mask? then is it correct to convert to 8bit and save as jpg? and then load into max with 1.0 gamma?
Yes to everything.

Quote from: johnymrazko
In your last screenshot you showed that it is possible to avoid Corona Sun completely and use only masked sun to create direct light right? that 9999 rgb x 37 rgb is based on Corona Sun + Sky setup? matching 117 RGB value?
Yes. I calibrated the HDRi sun to match isolated Corona Sun. Both will produce the exact same result.

Quote from: johnymrazko
Also when using that hdri in real world scenario can I adjust exposure in framebuffer to my liking?
True albedo matching is only necessary when we want to calibrate light and materials to real world values. When it's calibrated, you can use whatever you want to set  the mood.
If online stores could spend 1min extra when shooting HDRis, and just take a few pictures of a Color Checker or a 18% grey sphere. We could calibrate our HDRis to the actual capture.

Quote from: johnymrazko
And how do you decide how large should the sun circle be? Do you include flares or only the sun disk?
In this case I looked up at the NoEmotion sun. Moved a Corona Sun until it was in the middle of the NoEmotion sun, because the NoEmotion sun was huge.
Then I placed a standard camera at 0,0,0 facing south (south is the standard HDRi direction, the sun will show up in the center). Threw on a CoronaCameraMod, and enabled Projection type "Spherical". Then I changed the render resolution to match the HDRi and made a HDRi of Corona Sun. This is my mask.

When it comes to sun size, I guess it depends on what look you are going for. Sun size will not increase the light intensity of the sun, it will only make the shadows softer.
Most HDRi captures have a sun size of 2.

43
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-07-25, 23:40:45 »
Thanks , one more question - how do you isolate sun from hdri? Output node creates a mask and then Corona mix map with black color where the sun is and sky map for the rest?

Or painting in photoshop?

Photoshop does not have 32bit floating point support, so if you open a HDRi in Photoshop and resave, it is basically ruined.

If you only have Photoshop, you can create a white mask where the sun is, and load it in 3dsMax as gamma 1.0
There are different methods you can split and add them together again, here is one example.



Affinity Photo has 32bit floating point support. So you can remove or isolate the sun inside the program.

44
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-07-25, 21:52:49 »
Thanks for the reply. What values did you use for sun and sky ? default size and intensity for both? sun in realistic mode? Framebuffer rule of -5,24 exposure from PG skies calibration probably doesn´t apply here or am I wrong?

I left everything at default settings and just aligned the sun to the HDRi sun. This particular sun angle needed -5.285 EV for true albedo.
Corona Sky is a dynamic map that changes once you add a Corona Sun, and then it changes based on sun angle. I used Light Mix to isolate Corona Sky from the Sun.

45
Work in Progress/Tests / Re: dubcats secret little hideout
« on: 2018-07-25, 19:44:01 »
regarding calibrating hdris - is it neccesary to do even if I use separate light source (Corona Sun) for direct light? - for example noemotion hdris have no shadows from the sun

Hey!

I would still adjust RGB Level to match Corona Sky values at least. Corona Sun will eat all the sky light from those low exposure HDRis.
And just to be sure, I would remove the low level sun. It will only get stronger if you adjust RGB Level.

If we combine Corona Sun and this NoEmotion HDRi without increasing the RGB Level, we won't even notice the HDRi.



If we do a quick sky calibration like this.




We can finally see the HDRi again.





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

I had a quick look at the free sample 3DCollective HDRi.

Looks like someone painted the sun with a large soft brush.
The sun value is 1079 times dimmer then Corona Sun.



Here is Corona Sun for size comparison




Pages: 1 2 [3] 4 5 ... 29