Re: Zbrush shading in XSI

["Tim Leydecker" <BauerOink(at)gmx.de>]

I canÂt provide a final rendertree but also thought
about the concept of the MatCap Material.

As far as IÂve figured, one would need three or four
types of nodes:

*Facing ratio/incidence
*gradient color inputs
*(bent) surface normal
*custom direction and distance vectors

The first part, getting the basic shading, seems
quite easy, map a gradient with colorentries at
key viewing (incidence) angles with colors sampled
by user.

You get a flat shaded object with colorvariations
blending between "full front" and "facing away".
The easiest example is directly mapping a linear
bw ramp based on the facing ratio, what incidence
should do. The concept is similar to BRDF shading,
except there is no difference in X/Y (screenspace) made.

Now, the tricky part is how to get the selfocclusion
to happen, based on adjacent vertices and Normalangles,
where steep angles between adjacent Normals should be
shaded darker than areas whereÂs no caveats or angles.

I donÂt know how to set up a rendertree that can "calculate"
intensity values based on adjacent faceÂs Normal values?

To get shadow, one would take a custom direction vector,
like a 45Â light from above, e.g. simply a custom facing ratio
and would mult itÂs intensity value ontop, maybe going the
extra mile and first taking the above selfocclusion into account,
by not simply multing but wheighting the effect a bit.

Reflections could be added or again filtered through self occlusion.

Specular would be added based on the above custom light angle
and intensity driven by ramp/gradient?

To sum it up, the tricky part for me is to get an intensity value
based on the angle of two adjacent Normals (in object space),
then add a distance threshold in sceneunits to also take into
account more than the next face but instead get an area.

The NVidia guys have a real-time demo (including the principles)
of real-time ambient occlusion by using diskshaped arealights
per point and sampling that somehow, itÂs somewhere on the dev site.

Cheers

tim





----- Original Message ----- 
From: "Mathieu Leclaire" <mleclair(at)hybride.com>
To: <XSI(at)Softimage.COM>
Sent: Tuesday, October 23, 2007 8:31 PM
Subject: RE: Zbrush shading in XSI


OK, Iâm still trying to replicate the Zbrush shader look in XSI. Anyone care 
to help?


Mathieu Leclaire
R&D Programmer
Hybride Technologies

"Yesterday is history, tomorrow is a mystery, today is a gift and that is 
why it's called the present"

-----Original Message-----
From: Bradley Gabe [mailto:withanar(at)stanwinston.com]
Sent: Wednesday, June 20, 2007 7:51 PM
To: XSI(at)Softimage.COM
Subject: Re: Zbrush shading in XSI

If I am not mistaken, he is referring to the real time shading look in 
Zbrush3. Regardless of the displacement or not, objects in Zbrush3 have a 
kind of real time subsurface shading look to them, not unlike a shaded 
marble or other semi transparent stone, which makes sense considering it's 
intended appeal to classical sculptors.

Because of this light model, everything in Zbrush3 looks more physically 
accurate than the default realtime shaders in XSI. And since we do a lot of 
Zbrush work here in tandem with XSI, I can foresee the same thing happening 
with clients growing attached to the Zbrush look, and our need to replicate 
it in XSI. So I'll be watching this thread with interest. :-)

-Brad



Not sure I understand the question.  Zbrush 2 and 3 use built in 
displacement maps to achieve their look within the app.  You can get the 
same look in XSI if you also bring in the displacment maps the zbrush can 
generate for that purpose.

I believe Zbrush 3 still needs an updated zmapper plugin to do this 
properly - which has not yet been released.

Adrian


On 6/20/07, Mathieu Leclaire < mleclair(at)hybride.com 
<mailto:mleclair(at)hybride.com> > wrote:
I'm repeating myself if you read my first email but first off, I don't know 
much about Zbrush so excuse my ignorance. I though I'd ask you guys first 
before digging into the software.



Any of you guys know what shader they are using in Zbrush? My modelers are 
working on a model in Zbrush and it looks all good but once they import it 
back into XSI, it doesn't look as good. Anyone know what they use? Any info 
somewhere on their shading system?



What happens is that the supervisor looks at the model in Zbrush and likes 
what he sees and then when we bring it back into XSI, it's not the same and 
it draws confusion. So I was wondering if anyone knew how to have the same 
kind of shading in both softwares?



Mathieu Leclaire

R&D Programmer

Hybride Technologies



"Yesterday is history, tomorrow is a mystery, today is a gift and that is 
why it's called the present"







--
Adrian Lopez
CEO | Director | Producer
Liquid Light Digital
Kingston, Jamaica
C:  876.381.2471
W: 876.978.6418

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

HD/SD Production | VFX & Animation | Production Management

--
Bradley R. Gabe | Senior Creature TD | Stan Winston Studio



---
Unsubscribe? Mail Majordomo(at)Softimage.COM with the following text in body:
unsubscribe xsi