Rough Specular reduces specularity amount?

[^Lele^]

Very Interesting Thread!
Might be one of those where something very cool happens in the end.

I 'm wondering if VRScans could possibly result in some kind of ChaosGroup BRDF sometime.
Wouldn't be supprised if they're already researching in that direction.

Ah!
So you never had the pleasure of using the hidden V-Ray BRDF in 1.5++ to 2.x?

[^Lele^]

Hi, and thanks for your OSL i will make further test using it.

To get the gradient i use a very simple scene, 90 planes 1º rotation each and 1.0 on a full Vray dome and orthographic camera. I share the scene in case you want to do some test. It´s not 100% accurate because render noise and because you can´t render 99.99º planes but i like to "visualize" this kind of data.

To get the curves i use Nuke, crop the black border and sampler to sample the gradient.

MAX 2014 Scene Link:
https://drive.google.com/open?id=0By...WZZSmpiMUJGSjQ

Best.

You da maaaaan!
I didn't know of the sampler node (and ended up writing my own gizmos to similar effects, which looked butt ugly.), and my goodness you make me overly happy just by knowing someone else actually cares about measuring stuff.
Adam, you made my day.

[joconnell]

You da maaaaan!
I didn't know of the sampler node (and ended up writing my own gizmos to similar effects, which looked butt ugly.), and my goodness you make me overly happy just by knowing someone else actually cares about measuring stuff.
Adam, you made my day.

There's only two places where measuring stuff matters. With cg nerds and somewhere else :P

[^Lele^]

There's only two places where measuring stuff matters. With cg nerds and somewhere else :P

with male cg nerds.

[Ihno]

Ah!
So you never had the pleasure of using the hidden V-Ray BRDF in 1.5++ to 2.x?

I jumped on this train just before 3.0 was released. And than I first had to care about the sampling. So no, I never had the pleasure.
You sound like its gone now. Didn't turned out so well?

[^Lele^]

I jumped on this train right before 3.0 was released. And than I frst had to care about the sampling. So, no I never had the pleasure.
You sound like its gone now. Didn't turned out so well?

Well, better ones came out, i guess.
The GGX (rather, GTR!) that's implemented in V-Ray is a custom one, with a few benefits, so it's not a straight port from the paper.

As for the VRscans, mmmh, they can already be used in average mode as, aptly, average BRDF representations of that material, but the whole point of them is the spatially varying behaviour, which can't be principled, pretty much by definition, for all material types.

What we have and use today are generalisations of responses which seem to fit a large set of materials, and yet all of them, and the simple fresnel response with them, fall to pieces, no less, in between 70 and 90 degrees of viewing angle, when compared to measured responses (see Disney PBS paper from 2012.).
Which is where VRScans come in handy, incidentally.

[vlado]

Yeah I agree. In fact, once I thought that a VrayFresnel map having all the bells and whistles like simple Fresnel (just IOR), Complex Fresnel, a Custom Curve like Output map and whatever makes sense PLUS a dropdown with Vray BRDF models and roughness would be ideal. But after trying Redshift, I like it's solution better. It's mostly the same, but instead of the usual Fresnel IOR field, there's a dropdown for how to input Fresnel.

I haven't looked at Redshift, my intention was to turn the Fresnel on/off option into a drop-down with values of "Disabled", "Simple" (which is what we have now), "Dielectric" (which would incorporate the dielectric Fresnel calculations into the BRDF calculations themselves) and maybe "Metallic" (for complex IOR).

Best regards,
Vlado

[adanmq]

Nice tests Adan! I'm providing the gradients, could you please generate the graphs also for Iray, ART and Redshift too? Results seem to vary considerably between renderers. My guess is that it's likely caused by different BRDF models/variations.

Eugenio i´m not 100% sure but looks like the gradients you send are not lineal, can you send me the EXR linear version?. I´m doing test on Iray and RS to.

You da maaaaan!
I didn't know of the sampler node (and ended up writing my own gizmos to similar effects, which looked butt ugly.), and my goodness you make me overly happy just by knowing someone else actually cares about measuring stuff.
Adam, you made my day.

Wow. I must confess i start caring about these things mainly because of you, Vlado, joconnell, and many other users of this forum so i´m glad you find this usefull :O. I think every artist needs to know more about the "magic" behind the engines it totally changes my mind, improves my work and makes me feel “in control” xD. This stuff sould be teached on CG Schools.

Best.

[joconnell]

Wow. I must confess i start caring about these things mainly because of you, Vlado, joconnell,

I apologise profusely.

[Vizioen]

Wow. I must confess i start caring about these things mainly because of you, Vlado, joconnell, and many other users of this forum so i´m glad you find this usefull :O. I think every artist needs to know more about the "magic" behind the engines it totally changes my mind, improves my work and makes me feel “in control” xD. This stuff sould be teached on CG Schools.

Best.

Ditto

I apologise profusely.

Apologies accepted.

[adanmq]

I apologise profusely.

jejejeje. You ruined my life

[soulburn3d]

my intention was to turn the Fresnel on/off option into a drop-down with values of "Disabled", "Simple" (which is what we have now), "Dielectric" (which would incorporate the dielectric Fresnel calculations into the BRDF calculations themselves) and maybe "Metallic" (for complex IOR).

Sounds like an excellent plan.

- Neil

[Midiaeffects]

Eugenio i´m not 100% sure but looks like the gradients you send are not lineal, can you send me the EXR linear version?. I´m doing test on Iray and RS to.

Damn, you're right Adan. But it doesn't matter as you are doing for IRay and RS anyway .

I haven't looked at Redshift, my intention was to turn the Fresnel on/off option into a drop-down with values of "Disabled", "Simple" (which is what we have now), "Dielectric" (which would incorporate the dielectric Fresnel calculations into the BRDF calculations themselves) and maybe "Metallic" (for complex IOR).

Best regards,
Vlado

Sounds great Vlado!

-Eugenio

[^Lele^]

It's a frontier, for research and very complex maths.
As all frontiers, it's both full of promise and of pitfalls.
I think it's fair to say everyone with a renderer on sale is aware of it, and everyone is trying to get there asap.
I am not sure nigh everyone's doing it right (that i can see. up to what was publicly available of this year's siggraph.), although there are some proposals which are bold to say the least (one even abandons the concept of surface in favour of shading a microfacet "foam". Having my inner physicist do cartwheels, and me looking with puppy eyes in the direction of the Coding department).
The thing is that resources are finite, and some of these papers are a bit too wild, but one would get to know only after a LOT of work went into it (see the Stochastic Flakes: fixing the original paper produced another siggraph paper. after a year or so of sweat and blood from Asen and Vlado.).
However, Chaos has a wealth of technology which is proprietary, including a freshly announced material scanner, now improved to scan translucency.
So hey, i personally wouldn't want to be in any other seat, as far as future shading advancements go... ^^

[joconnell]

now improved to scan translucency.

Um... what?