-----Original Message-----
From: owner-xsi(at)Softimage.COM
[mailto:owner-xsi(at)Softimage.COM] On Behalf Of peter boeykens
Sent: Tuesday, May 27, 2008 1:07 PM
To: XSI(at)Softimage.COM
Subject: Re: rendermap / lightmap SSS shader
Thanks for the link.
I am doing multiple rendermaps with the camera in different
positions, and recombining them - this gives me a fairly good result.
It's just a lot of work - mostly because of the very slow
rendering times and instability of rendermap.
A 2k rendermap is 1.5 hours on average on the stuff I'm
working on - regular 2k renders are less than 15 minutes. I'm
scripting overnight renders of several rendermaps which helps
out a lot - but one night out of two rendermap either
crashes, freezes or simply disappears.
...
----- Original Message -----
From: "Halfdan Ingvarsson" <hingvars(at)Softimage.COM>
To: <XSI(at)Softimage.COM>
Sent: Tuesday, May 27, 2008 5:06 PM
Subject: RE: rendermap / lightmap SSS shader
It's not complicated what it does. It's basically a trick
they used on
Finding Nemo, described in some Siggraph notes, but using the
camera's pov,
rather than the light's pov. (see:
http://graphics.stanford.edu/facecourse/facecloning05/Presenta
tions/scat.pdf
)
The lightmap contains the interleaved illumination of the
front and back
surfaces (+depth of back) as seen from the camera, then the
fast_sss shader
simply blurs the image samples based on distance, for each
sample lookup.
This is why this trick won't work in a wraparound mode. If
you froze the
lightmap and then orbited, the SSS effect would look quite
funky where you
were viewing perpendicular to what the original camera's
sampling position
was.
The only decent way to do it would be something along the
lines of what Alan
describes.
- ½
-----Original Message-----
From: owner-xsi(at)Softimage.COM
[mailto:owner-xsi(at)Softimage.COM] On Behalf Of
Alan Jones
Sent: 27-May-2008 10:55
To: XSI(at)Softimage.COM
Subject: Re: rendermap / lightmap SSS shader
On Tue, May 27, 2008 at 3:20 PM, peter boeykens
<peter_b(at)skynet.be> wrote:
> For "unsupporting" SSS - this seems lame - as it wouldn't take all
> that much to get it to work.
> The downfall is with the lightmap being camera dependent.
> I dont think that's a limitation of lightmaps - as color sampler
> lightmap is working with UV space.
The fast SSS shaders don't do anything akin to an ordinary
lightmap in UV
space.
They use lots of strange trickery behind the scenes to do
their work and Zap
is very tight lipped on their secret sauce used. Don't forget
that Halfy is
an exceptionally intelligent guy, if there was something on
his end he could
do to resolve this it would already be done.
There's nothing stopping you from writing/employing someone
to write your
own SSS shader which could achieve similar speed using
lightmaps by doing
some nice trickery to store to a kdtree/bih instead of a UV
space texutre
and then looking that up within the main shader. It'd be nice
and fast and
you'd avoid the camera dependency that makes fast SSS so unhappy.
Though if you use SSS a lot grab a copy of 3Delight - their SSS is
absolutely gorgeous, though I've not look at whether they support
rendermapping in XSI, though I'm sure Aghiles would be more
than happy to
provide customers with something that does this within XSI in
order to get
3Delight into a new facility.
Cheers,
Alan.
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