PDA

View Full Version : transparency based on geometry thickness


seb4d
09-21-2004, 11:36 AM
Hi !
I was wondering if it is possible to create a shading network that adapts transparency of an object based on its thickness ?

Ablefish
09-21-2004, 04:10 PM
As in a volume or SSS shader? Check out Daniel Rind's site for his diffusion shader... http://animus.brinkster.net/index.html

seb4d
09-21-2004, 05:12 PM
Yes maybe the diffusion shader could do the trick, but how would you connect it to the transparency attribute ?
Concerning volume shader I don't really know it, so I have no idea how it could be usefull.
I need to investigate more.

Ablefish
09-22-2004, 01:30 AM
You can actually plug the diffusion shader into transparency, but only if the tree you're plugging it into is plugged only into the Material's Surface input. It won't connect if its still plugged into Shadow or Photon.

There are other shaders with this limit on them, so keep it in mind if one time you're trying to plug an rgb output into an rgb input and it won't work.
One other thing... if you're just driving transparency, you might just use white and black in the diffusion shader, but don't make the Absorption 0 or it won't work. 0.001 will do just fine though.

wurp
09-22-2004, 10:14 AM
There is a thickness shader if you look under nodes->raytracing->more


it should return the thickness of the object as a scalar value, not sure if it will do the job but you could try it out.

seb4d
09-22-2004, 10:28 AM
Thank you for your help Ablefish and wurp ! These are two different interesting approaches of the problem.
I'll try what you said :thumbsup:
Cheers.

Sebastien

MJV
11-11-2004, 05:51 AM
Thank you for your help Ablefish and wurp ! These are two different interesting approaches of the problem.
I'll try what you said :thumbsup:
Cheers.

Sebastien
Hi. I'm curious if you tried these two methods and what you found. Thanks.

seb4d
11-11-2004, 11:42 AM
The thickness shader gave me the result I expected, very easy to use. I first plugged it into the diffuse slot to see the black and white parts, then plugged it into the transparency slot.
I tried Diffusion but didn't manage to get a satisfying result.

MJV
11-11-2004, 11:45 AM
The thickness shader gave me the result I expected, very easy to use. I first plugged it into the diffuse slot to see the black and white parts, then plugged it into the transparency slot.
I tried Diffusion but didn't manage to get a satisfying result.
Cool. Thanks.

sundialsvc4
11-11-2004, 01:22 PM
I did something like this for a shot of a Fresnel lens at the top of a lighthouse. As it happened I was using a tool that didn't have a thickness shader, but I could fairly easily produce a depth-map. And I used that map to control a variety of effects. The reason why I mention it is that I wound up taking the map and tweaking it in PhotoShop -- partly because it turns out that realism called for more than simply "the thickness of the glass." (Of course there are lots of light-paths through a Fresnel; it's a lens after all...)

So, something as utterly low-tech as a map and a digital paintbrush allowed me to modify the final effects quickly. I recall also that this was a "fool the eye" situation because it only took a few tweaks in the most-obvious areas; it wasn't necessary to get literally-true accuracy throughout the frame. Now it must be said, the lens wasn't moving...

I was also very happy to observe that the computer took more time to generate the map -- which it only had to do once -- than it ever took to simply use that map to subsequently control a variety of effects layers. (My equipment is, to put it very politely, "slow"... :banghead: :argh: ...)

CGTalk Moderation
01-19-2006, 08:00 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.