Volume caustics and SSS

[sonne]

I was wondering if this can be done in a standard XSI: http://www.motiondesign.biz/

Thanx,
Peter

[atyss]

The top paragraph says it's been done with mental ray in Maya. I'm not sure what you refer to as "standard XSI".

Salutations - Cheers
Bernard Lebel

[sonne]

Hi Bernard,

What I mean is: Can it be done in XSI without any shader writing?
I'm asking because as far as I know, MR can do just about anything, but MR in XSI can't without some kind of shader writing. Maybe when they created the MR port for Maya, some shaders where written that are not in the XSI version? I don't know, and that is why I'm asking, if it can be done in XSI using the render tree.

/Peter

[atyss]

Yes it can be done but it's not a single click process, though it doesn't require coding. However, note that in XSI you don't have access to all the features of mental ray through the interface. You have to hack .mi files (well, to code) to access such functions. You asked this question to XSI list, right? Bartek listed some of the things, in this particular case, that you can't access in XSI.

So the best way to do it is by using the Volume_effect node, connected in the Volume of the Material node. See how to use it here:
http://www.tomsporer.com/html/body\_shader\_...iption\_wax.html
http://www.tomsporer.com/html/body\_shader\_...ption\_blue.html

Unfortunaly, this leaves out all the Photon effects that you see in that Maya tutorial.

Hope this helps
Salutations - Cheers
Bernard Lebel

[devdoka]

@@@What I mean is: Can it be done in XSI without any shader writing?

Short answer: No.

Matt

---

Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com

[sonne]

Thanx Matt and Bernard.
That's not the answer I hoped for , but who knows.. maybe it'll be there in the next version on XSI.

/Peter

[srvargas]

Bernard,
can you put a link to this discussion of things that can and cannot be done with Bartek. I searched the softimage discussion groups but couldn't finf anything...10x in advance

[atyss]

Read the first here:
http://www.highend3d.com/xsi/archive/sp.3d?mail\_id=44569

Bartek's answer:
http://www.highend3d.com/xsi/archive/sp.3d?mail\_id=44578

Sorry, it wasn't you who started that thread

Salutations - Cheers
Bernard Lebel

[srvargas]

Well I certainly think that the solution Maya/Mental Ray offers is not subsurface scattering at all (neither is XSI's). It is just a volumic shader applied on an object (meaning that the object is always transparent and looks like smoked glass). Having read Henrik Van Jenssen papers on scattering and looking at the pictures he shows the closest thing to real SSS is the XSI TransVol shader. That shader is still in early stage but shows real promise.
Anyway, with xsi/mental ray SSS is not a problem - only a shader needs to be written (Van Jenssen uses a MonteCarlo raytracer for his research, and there is a technique he implemented that allows for really fast/high quality scattering with GI turned on). In his papers SSS is even implemented in PRman (which is scanline) - perhaps a trick could also work - no fancy raymarching, etc.