Chaos Corona Forum

Chaos Corona for 3ds Max => [Max] General Discussion => Topic started by: Juraj on 2014-02-19, 21:55:54

Title: Polarization [filters]
Post by: Juraj on 2014-02-19, 21:55:54

I always kind of wondered, if this effect was simulated in-render by any renderer. Wasn't really able to search out anything on it.
Some of the effects of polarizing filter in photography can be of course achieved, atleast on surface visually, in post-production, but not all of it,
is it affects reflections quite a lot.

Seems there is very little interest on it, not sure what I am missing. Seems to be imho great contributor in pleasing photorealism.

Title: Re: Polarization [filters]
Post by: Ondra on 2014-02-20, 02:51:59

we (at school) have renderers that do polarizaton. I think I saw somewhere that maxwell does it. Of course what is actually done is gross simplification of the reality. Corona does not support it.

Title: Re: Polarization [filters]
Post by: maru on 2014-02-20, 10:40:09

From what I see using a polarization filter works close to lowering material's fresnel reflection IOR. Maybe it could be faked? "Global fresnel IOR multiplier"? :)

Title: Re: Polarization [filters]
Post by: Ondra on 2014-02-20, 11:01:11

Quote from: maru on 2014-02-20, 10:40:09

From what I see using a polarization filter works close to lowering material's fresnel reflection IOR. Maybe it could be faked? "Global fresnel IOR multiplier"? :)

Nope. Polarization filters work very differently

Title: Re: Polarization [filters]
Post by: Utroll on 2014-02-20, 12:09:05

and metal does not affect reflected light, so they should be excluded from any global multiplier. Honnestly, I bought one for my camera years ago, I used it may be 10 times... I'm not convinced it's a prioritary feature nowadays :D

It was done in 1987 already though http://kurlander.net/DJ/Projects/Polar/resources.html
And at page 51 from his publication you can read that on average it doubled the calculation time ~vade retro~

Title: Re: Polarization [filters]
Post by: Juraj on 2014-02-20, 13:09:01

Definitely not some priority. Doesn't fit newly bought Nikon 14-24mm/2.8G ED lens either :- ) But I personally was always fan of the effect in certain situations and wasn't aware how this translates to CGI. I was just buffled than no one ever mentioned it.

Title: Re: Polarization [filters]
Post by: arqrenderz on 2014-02-20, 14:53:05

This lense¿¿¿ Nikon AF-S Zoom Nikkor 14-24mm f/2.8G ED AF Lens?
Wow! what camera are you using with it?

Title: Re: Polarization [filters]
Post by: Mr.Max on 2024-09-29, 12:16:50

I was looking into this recently and I found this interesting paper that talk about it for Realtime Rendering

https://jcgt.org/published/0010/02/03/ (https://jcgt.org/published/0010/02/03/)

It show examples for multiple materials with and without the polarization. It's interesting how it acts differently from one material to another.