new architectural shader parameters in 2011 - perhaps Halfdan's listening....

[Andi Farhall]

I've only just noticed that the architectural in 2011 (sp1) has gained a second reflection part called "base reflection". Sadly I cant find any mention of it anywhere……….. the xsi manuals have no mention of it - mental images own documentation for the architectural shader has no mention of it - the xsi-wiki document is 4 years old……

 

it's a bit like getting you car back from the garage to discover a large red button has been installed into the dashboard that nobody knows anything about.

 

I could through testing come up with a theory of what it does, but it's nothing like having first hand info from the manufacturers…..

 

So, Halfy, any chance you could give us the downlow on it? How it works in relation to the first reflection parameter?

 

 

Cheers

 

Andi.

[Steffen Dünner]

Great question, Andi!

This new reflection stuff must have silently slipped into the SP1 somehow it seems. No documentation on it so far. I could imagine it could become useful for something like secondary reflection layers or coatings, but so far I've not found out how to give the 2 reflections a different falloff curve or IOR.

Lets see what Halfdan will say... :)

Regards

Steffen

2010/7/7 Andi Farhall <andi.f...@primefocusworld.com>

--
PGP-ID(RSA): 0xCCE2E989 / 0xE045734C CCE2E989
Fingerprint: 394B 3DA9 9A9A 96C6  3A5A 0595 EF92 EE1F

[Matt]

Great to see that this finally made it in there ;)

If it is made to create clearcoat style reflections, what makes it awkward is the fact that you don't have seperate controls over the fresnel value of both reflectivities, like Steffen mentions. Seems like the "Reflection reflectivity" value is kind of the master control, and the base reflectivity is mixed into the result. To make a proper car shader, or any surface that gets a clearcoat style coating, you need control over both fresnel curves of the base coat and the clear coat, and correct energy conservation between both reflections.

Guess I will have to keep making my own for now!

--
Matthew Rouleau
www.theembassyvfx.com

[Daniel Rajcic]

Hi all

I asked Zak from mental images about this new property on the fxphd forums.

His "public" answer is this:

=========================================================================================================

 

This is a 2nd glossy layer. It saves you having to blend materials to just have 2 layers of glossiness. I didn't implement it and I would probably have implemented it slightly differently. It's great for doing, oh, stuff like Iron Man suits 

Basically, "base reflectivity" is a percentage (0-1 range) of how much of the "reflectivity" is handled by this layer. 

0 means all reflectivity comes from the normal reflection controls (above this). 1 means all reflectivity comes from these reflection controls. 0.5 means a 50/50 mix of the two.

That's basically it.

 

=========================================================================================================

 

On a side note - Zak is repeating his mental ray course this term on fxphd.com. For all of you that want to get a deeper understanding of how mental ray works and how to use it in production, I highly recommend this course!

 

cheers,

Daniel

[Daniel Rajcic]

Sorry. Don't wanna spam. Just to clarify. I ment Zap Anderson, and not Zak, as I realised as soon as I clicked the send button.

 

 

From: Matt

Sent: Thursday, July 08, 2010 1:27 AM

To: soft...@listproc.autodesk.com

Subject: Re: new architectural shader parameters in 2011 - perhaps Halfdan's listening....

[Adrian Lopez]

Sounds very similar to the carpaint shader...   wait, wasnt the Iron Man suit painted with car paint?

Adrian

[Steffen Dünner]

All this sounds very nice, but without separate falloff curves it's useless for many things. For carpaint you need at least a highly reflective, metallic bottom layer and a clear coating layer with completely different fresnel coefficients and different glossy settings. Maybe it's just missing in the GUI at the moment.

Regards

Steffen

2010/7/8 Adrian Lopez <vfx...@gmail.com>

[Sebastian Kowalski]

nice to have it, but why you guys need both reflections at once? seperate refl buffers make more sense for compositiong to me.
just curious

[Guillaume Laferriere]

Here is the answer from the author of the parameters:



"These parameters add a second glossy lobe to mia_material, like another layer of glossy reflections below the normal glossy reflections.



It is really quite simple; the material works exactly as before, with all the weighting of reflectivities etc. exactly as documented.



However, the refl_base parameter is a weight between the normal reflectivity settings and the new "base" reflection.



refl_base = 0 ==> Only using normal reflection values

refl_base = 1 ==> Only using the refl_base_* values

refl_base = 0.5 ==> 50/50 mix of both reflections



This allows you to do something like a coated metal or carpaint style material in a single mia_material without having to resort to layering and blending multiple materials. In general, one uses the "refl_base_*"

for a slightly glossy reflection with the same color as the diffuse, and then use a sharp (refl_glossiness=1) reflection as a clearcoat layer on top with a white reflectivity color. (I.e. think Iron Man Suit material)



The "reflectivity" parameters and the "brdf_*" parameters still guide the overall reflectivity, and "refl_base" is simply an interpolator that chooses how much of which of the two different reflections are actually used.

From: softimag...@listproc.autodesk.com [mailto:softimag...@listproc.autodesk.com] On Behalf Of Sebastian Kowalski
Sent: July-08-10 5:38 AM
To: soft...@listproc.autodesk.com
Subject: Re: new architectural shader parameters in 2011 - perhaps Halfdan's listening....

nice to have it, but why you guys need both reflections at once? seperate refl buffers make more sense for compositiong to me.
just curious

Am 08/07/2010 11:30, schrieb Steffen Dünner:
All this sounds very nice, but without separate falloff curves it's useless for many things. For carpaint you need at least a highly reflective, metallic bottom layer and a clear coating layer with completely different fresnel coefficients and different glossy settings. Maybe it's just missing in the GUI at the moment.

Regards
Steffen

2010/7/8 Adrian Lopez <vfx...@gmail.com<mailto:vfx...@gmail.com>>

Sounds very similar to the carpaint shader... wait, wasnt the Iron Man suit painted with car paint?

Adrian

On Thu, Jul 8, 2010 at 2:50 AM, Daniel Rajcic <daniel...@gmail.com<mailto:daniel...@gmail.com>> wrote:
Hi all
I asked Zak from mental images about this new property on the fxphd forums.
His "public" answer is this:
=========================================================================================================

This is a 2nd glossy layer. It saves you having to blend materials to just have 2 layers of glossiness. I didn't implement it and I would probably have implemented it slightly differently. It's great for doing, oh, stuff like Iron Man suits [cid:image0...@01CB1E97.EF55E570]

Basically, "base reflectivity" is a percentage (0-1 range) of how much of the "reflectivity" is handled by this layer.

0 means all reflectivity comes from the normal reflection controls (above this). 1 means all reflectivity comes from these reflection controls. 0.5 means a 50/50 mix of the two.

That's basically it.

=========================================================================================================

On a side note - Zak is repeating his mental ray course this term on fxphd.com<http://fxphd.com>. For all of you that want to get a deeper understanding of how mental ray works and how to use it in production, I highly recommend this course!

cheers,
Daniel

From: Matt<mailto:matt.r...@gmail.com>
Sent: Thursday, July 08, 2010 1:27 AM
To: soft...@listproc.autodesk.com<mailto:soft...@listproc.autodesk.com>
Subject: Re: new architectural shader parameters in 2011 - perhaps Halfdan's listening....

Great to see that this finally made it in there ;)

If it is made to create clearcoat style reflections, what makes it awkward is the fact that you don't have seperate controls over the fresnel value of both reflectivities, like Steffen mentions. Seems like the "Reflection reflectivity" value is kind of the master control, and the base reflectivity is mixed into the result. To make a proper car shader, or any surface that gets a clearcoat style coating, you need control over both fresnel curves of the base coat and the clear coat, and correct energy conservation between both reflections.

Guess I will have to keep making my own for now!

--
Matthew Rouleau

www.theembassyvfx.com<http://www.theembassyvfx.com>