Re: Zbrush shading in XSI

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

Starting to read up on shader writing for mentalray
(umhh, copy&paste for phenomena, to be true...)
I´ve stumbled across tAmaan Akram´s shading theory:
http://www.mymentalray.com/mymr_tutorials/tutorials_custom_tutorials/Shading%20theory_Lesson4.htm

The interesting bit (judged by my limited knowledge)

Vector A = (X1, Y1, Z1)
Vector B = (X2, Y2, Z2)

Given that vectors A and B have been Normalized:

Cos (theta) = (X1*X2) + (Y1*Y2) + (Z1*Z2)

is that one might (?) be able to use that in form of a
Normal map to drive a gradient for selfshadowing?

Especially if there´d be a way to define a threshold
area (or volume) in which face orientation is compared?

I know, most people will probably laugh at my
childish approach, it´s based on learned artisitic
practice, eyeballing a surface (or area) to guesstimate
wether it should be lit or shadowed while trying to paint it...

Cheers

tim





----- Original Message ----- 
From: "Alan" <alan.fregtman(at)gmail.com>
To: <XSI(at)Softimage.COM>
Sent: Tuesday, October 30, 2007 2:45 AM
Subject: Re: Zbrush shading in XSI


> And speaking of neat realtime lighting, the absolute best would be
> Pixar's "Lpics" propietary realtime lighting software:
>
> http://graphics.pixar.com/Lpics/lpics_siggraph.mp4
> http://graphics.pixar.com/Lpics/paper.pdf
>
> > From Siggraph 2005. One can only imagine how much more advanced or
> faster it probably is in the present day. :o
>
>   -- Alan Fregtman
>
>
> On 10/26/07, Tim Leydecker <BauerOink(at)gmx.de> wrote:
> > Hi Mathieu,
> >
> > did you see any progress sofar?
> >
> > I guess you allready know Andy Nicholas´ Postlight?
> >
> > http://www.andynicholas.com/thezone/index.php?area=downloadinfo&app=XSI5&file=0
> >
> > and the Taron/Spoeth ZBornToy:
> >
> > http://www.frischluft.com/zborntoy/zborntoy.php
> >
> >
> > Both aren´t strictly realtime but still interesting in their
> > approach, should at least be inspiring in terms of splitting
> > up a "realistic realtime shader" into components and
> > identifying the required buffers/passes/calculations?
> >
> > Personally, I wonder why something like postlight
> > (in a streamlined implementation) isn´t the default
> > way of the viewport giving user feedback?
> >
> > Whatever, instead of just mimicking ZBrush´s (beautiful)
> > viewport/shaders, I´d love to have that coupled with
> > a full-throttle control for lights, surfaces and reflections...
> >
> > Including "satellite nodes" for extra viewport redraw...
> >
> > Cheers
> >
> > tim
> >
> >
> >
> >
> >
> >
> > ---
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