Cool Translucence

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Old 03 March 2003   #1
Question Cool Translucence

the other day I checked out techtv.com and found some stuff from eye drops in one of the animation lab things. in it they had some stuff about making translucent shaders. you know for stuff like leaves skin marble milk and other stuff.
so naturally I go to maya and try it out. I experimented for hours with the translucency attributes and no change in my objects at all.

How do you get translucency to work good.


Hey, just to clear things up this thread is about SSS effects and stuff.
I didn't really mean translucency in the thread title. I just called it that because I didn't know what it was really called.
and for some of you that doesn't know what this is. SSS stands for sub-surface scattering. you know. when light hits your surface some goes in and dances a jig and then bounces back out.
(I didn't know this kind of cool stuff existed like 3 days before I started this thread.)

Last edited by Maya Ayanami : 04 April 2003 at 03:49 AM.
 
Old 03 March 2003   #2
Maya handles translucency pretty simple: shine a light behind it and the light shines through. I think what you expected was some kind of sub-surface scattering, that is when light travels through the material and bounces back colors and light from within the material. It's quite possible to do with Mental ray, it just needs some clever shader-writing.
I think I have a link to a tut somewhere... hm, must have it at work... I'll be back.
 
Old 03 March 2003   #3
yep... that is the thing I am talking about.
is it hard..
 
Old 03 March 2003   #4
pixho has a nice sss fake maya shader on his site (www.pixho.com)

check that out

cheers

alexx
 
Old 03 March 2003   #5
the images in maya's documentation on translucence look pretty decent - i guess it depends on what kind of translucent material you are trying to achieve

and there's a sss simulation (fake) tutorial for mental-ray on the net
 
Old 03 March 2003   #6
"the images in maya's documentation on translucence look pretty decent - i guess it depends on what kind of translucent material you are trying to achieve"

It had better be a thin surface, like a leaf, paper, or lampshade. Notice how the docs only show sample images of leaves (thin surfaces) but claim in the text that translucency depth and focus can carry light though things like styrofoam balls, etc.? The reality is, the translucency function in Maya is "broken" for non-thin surfaces, and on thicker objects like spheres the function can't really allow any of the light to carry through the surface correctly. If you try what they say in the docs, you'll be dissappointed. That's why the text goes further than the sample images - the poarameters are there, but the functions don't actually work.

"and there's a sss simulation (fake) tutorial for mental-ray on the net"

Again, disappointing. Most of the tutorials on sss describe how to make things like smokey glass, things that are more like modified transparency than sss as seen in marble, wax, human skin, milk, etc.

-jeremy
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Author, Digital Lighting & Rendering, 3rd Edition
 
Old 03 March 2003   #7
do any of you know about a mental ray shader type thing in mental. see pic. first red circle. ignore the other.
 
Old 03 March 2003   #8
Could you use a volume shader to achive an SSS effect.
 
Old 03 March 2003   #9
There have been some recent threads about DGS on highend3d, including:
http://www.highend3d.com/boards/sho...sb=5&o=0&fpart=
and some other threads about problems with shadows on DGS, etc.

A good photon volume shader could certainly be a way to write a SSS shader for Mental Ray.

-jeremy
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Author, Digital Lighting & Rendering, 3rd Edition
 
Old 03 March 2003   #10
The tut I mentioned was probably the same as Jeremy dizzed. It's mainly colored smoked glass type of things. However here's the link:
http://www.motiondesign.biz/

Haven't tried it myself though. Thought I'd do it when things quiet down here at work. My main goal is making a really stunning translucent skin texture. Guess I'll just have to keep looking then
 
Old 03 March 2003   #11
Translucency

I read somewhere that the maya implementation of translucency requires that transparency be set to a non-zero number
(ie. 0.001) in the common attributes of the material, before the translucency effect works....
Works for me!
Also the SSS script update from pixho.com is DEFINITELY worth putting to use...

ATWOOKI
 
Old 03 March 2003   #12
why its hard

I think the reason why its hard to do SSS is because different material behave differently based on their material made from.

For example theres marble tranclucency, that along have variation of of SSS depending on the quality of marble.

Thats why A|W's made its own shader for skin, its mostly improved for translucency.

It depents what matrial you focus on, if you are an artist and dont have a greate since of direction yet, then its hard to come up with one, just by playing around shader nodes.

On the otherhand if you intend to achieve a certain SSS effect for a particular material, say you really like the Marble shader in siggraph few years back, then just have a look around the net for their papers, how they do it and try mimic the same with shaders in maya, look for the way they handel lights and interpret shading effects.

Its always easy if you know exactly what you want.
 
Old 03 March 2003   #13
"Its always easy if you know exactly what you want."

I know a lot of R&D people who don't find this easy, and you're the first person I've met who's suggested that it was easy for you. Where do you work? Can you share your results?

I'd like human skin, and I have lots of reference images of exactly what I want, and how the shading should work on the bottom of someone's nose where the light is cast through the cartilage and adding a warm reddish glow to the nose interior and pink fill cast into part of the shadow area underneath. Now, will it be easy? Or is translucency completely broken the moment you turn on shadows or use complex geometry? Can you even get the SS color you want to appear on the bottom of the nose?

-jeremy
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Jeremy Birn
Author, Digital Lighting & Rendering, 3rd Edition
 
Old 03 March 2003   #14
Quote: Originally posted by jeremybirn
"Its always easy if you know exactly what you want."

I know a lot of R&D people who don't find this easy, and you're the first person I've met who's suggested that it was easy for you. Where do you work? Can you share your results?

I'd like human skin, and I have lots of reference images of exactly what I want, and how the shading should work on the bottom of someone's nose where the light is cast through the cartilage and adding a warm reddish glow to the nose interior and pink fill cast into part of the shadow area underneath. Now, will it be easy? Or is translucency completely broken the moment you turn on shadows or use complex geometry? Can you even get the SS color you want to appear on the bottom of the nose?

-jeremy


Too bloody true Jeremy
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Old 03 March 2003   #15
I dont work for any studio.

I was suggestion its easier if you have refence to wrok from, still I know its difficult to come up with a general SSS solution.

I'll say for maya rendering, and doing skin stuff, you can get good results by connecting shaders. Some suggestion would be using forward scatter in ramp shader(skins have a higher foward scatter), and use facing ratio to drive Foward scatter and translucent attributes to mimic pinkish colors on the out side.
 
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