Author Topic: GGX - best way to recreate it for all metals, problems translating to Corona  (Read 58867 times)

2014-08-05, 23:15:26
Reply #60

Juraj Talcik

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C4D R16 just implemented GGX and multi layer reflections: http://maxonexchange.de/pr/Cinema_4D_R16/Cinema_4D_R16_PS_Reflectance.jpg

That looks quite interesting to be honest. Cinema seems to fight hard these days, building Arnold plugin themselves, now this. A dev who listens to users and act too :- ) ?
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2014-08-05, 23:39:38
Reply #61

Javadevil

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I don't know what you mean by one layer. The objects is rendered on one layer and the material may be one layer, but he is clearly setting up another layer of reflection glossiness. You get two layers: one that is more "shiny" and one that is more "blurry". This is not what happens in real life. You would need A LOT (or preferably infinite amount) of layers with different glossiness levels.

Here is my visualization of what happens. Sorry if what I write and show does not make any sense, I'm having a killer headache. :>

Maru I am agreeing with you, in real life, that paint would only be one material, it shouldn't have to be layered to create it.
I thinking of layers in how many different types of coats are on the wall, like I said it doesn't have a clear coat of varnish to create the second specular reflection.
If it did then I'd layer the material.

cheers

2014-11-14, 08:25:03
Reply #62

daniel.reutersward

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Hi,

Old topic and maybe the wrong place to post this but I saw Grant Warwick post this on his Facebook page and thought it might be interesting.

Does anybody know if this is some more advanced version of the ggx shader?

http://help.chaosgroup.com/vray/images/stuff/gtr_tests/gtr_render.html

/Daniel

2014-11-14, 16:35:08
Reply #63

Juraj Talcik

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Does anybody know if this is some more advanced version of the ggx shader?


It's clearly written what it is on that page :- )

"Generalized-Trowbridge-Reitz BRDF as described in the paper "Physically-Based Shading at Disney". It is an extended version of the GGX BRDF"
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2014-11-14, 16:42:47
Reply #64

daniel.reutersward

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It's clearly written what it is on that page :- )

"Generalized-Trowbridge-Reitz BRDF as described in the paper "Physically-Based Shading at Disney". It is an extended version of the GGX BRDF"

I must have missed that (using my phone), but that sounds interesting! Trying to get my head around the physically based shading world :)

2015-02-22, 00:06:49
Reply #65

twoheads

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I did some random tests lately. Semi distressed copper is what I'm trying to create, quite happy with the result so far (but not super happy) I love Daniel's copper BTW.

TH

copper_test_distressed. by twoheadscom, on Flickr

2016-04-27, 00:22:59
Reply #66

Fluss

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I posted this in another topic (https://corona-renderer.com/forum/index.php?topic=9489.msg75492#msg75492) but i think here is a better place.
I found this today. It might interest you guys, if you have not seen it yet

and
https://eheitzresearch.wordpress.com/240-2/
« Last Edit: 2016-04-27, 09:53:11 by Fluss »

2016-05-01, 11:38:32
Reply #67

Siahpoosh

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I posted this in another topic (https://corona-renderer.com/forum/index.php?topic=9489.msg75492#msg75492) but i think here is a better place.
I found this today. It might interest you guys, if you have not seen it yet

and
https://eheitzresearch.wordpress.com/240-2/

really interesting solution , you should make a feature request topic for this , hope corona add this in future ,

2016-05-04, 12:52:41
Reply #68

Fluss

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yup, that looks very promising, especially when it comes to energy preservation. But it looks like it should be quite intensive in terms of calculation. Would like to know Ondra's opinion about it.

2016-05-12, 15:05:09
Reply #69

Jarda

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Hey guys,

I'm in charge of research in Corona so I took a thorough look at the paper. I came to the conclusion that it is not very useful for Corona at this point, for the following reasons.

First there is the overhead: for some rough refractive surfaces, the render time can get almost twice longer with the method in the paper - definitely not something we would want to see in Corona.

Second, what does the paper really has to offer in exchange for this overhead? In fact, nothing that Corona wouldn't already have.
What they use is the usual microfacet BRDF (such as GGX) but they can ensure that energy is preserved as the roughness/glossiness changes. In other words, the material does not get darker/brighter as you tweak glossiness.
But we already have a different solution for exactly the same problem in Corona which works just fine. Try to play around with CoronaMtl and you should be able to see that there is actually no darkening as you change the reflection glossiness.
Current version of Corona still has some issues with energy preservation of rough *refraction*, but we already have implemented a solution that works very well and we will release it in a daily build soon after 1.4.

So there's probably not much to get out of this paper for Corona.

Cheers,
Jaroslav