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View Full Version : How to use Surface Thickness Gradients???



roberthurt
03-07-2003, 12:54 PM
I've been trying to play around with the new surface thickness gradient but I may be missing something. Can anyone give an example of how this is supposed to be used?

I applied it to various surface properties of a sphere, under the assumption that the "thickness" of the surface was a measure of how far a ray travels before coming out of the other side. However, any parameter I set merely defaults to the value given to a thickness of 0.0.

I was hoping this might be useful for faking some volumetric effects.

If anyone can suggest a simple formula to see how this works I'd greatly appreciate it!

Matt
03-07-2003, 02:07 PM
I can make it have an effect on my surface, but I'm not sure what it's doing _exactly_.

Controlling whatever input you apply it to by surface thickness yes, but I can't control
it if I don't know HOW it's doing it!

A good explanation would be good!

Skonk
03-07-2003, 02:07 PM
Make sure u turn on Raytraced Transparency and make the surface double sided.

James..

Matt
03-07-2003, 02:42 PM
doh! of course think about it!

if your object isn't slightly translucent or transparent (or both) how can you see 'into' its surface thickness?

not sure if I'm using it exactly as intended but this is my first mess about with it . . . a ball of wax!!!

I'm sure someone else can do A LOT better!!!

roberthurt
03-07-2003, 04:04 PM
Matt,

I'm not sure what the surface thickness is doing in that render... what's going on there aside from what you'd expect with flat translucency/transparency and double-sided settings?

Matt
03-07-2003, 04:35 PM
I'm not too sure it seemed to do something when I was playing with it!

I think it might be too subtle, but like I said other people will be
able to create better results, I'm not the greatest LightWave
artist here by any stretch of the imagination!!!

DarkEkko
03-07-2003, 11:23 PM
the surface must be double sided, or have a set of "air" polys facing inwards;

'surface thickness' evaluates thickness according to the polygon normal.

sooooooooo... if your polygons normals are facing OUTWARD, there arent any polygons to run into and register 'thickness'.

Wade
03-08-2003, 01:33 AM
Just playing for a moment and well I think what it does is measure the thickness of the object from the viewpoint of the camera. Then it assigns a color based on a gradient. No need for transparency, refraction, air polys or anything really.

So if your gradient specifies that it is red if 2 feet thick then it is red when 2 feet thick as the camera sees it.

Set your gradient to a unit of measure to relates to your object’s size…

Wade
:)

Wade
03-08-2003, 02:03 AM
It’s looking at the distance between the surface that the camera sees and the next surface behind it. Then your “thickness gradient” assigns the color.


Wade

Wade
03-08-2003, 02:12 AM
My objects were feet tall and feet thick so I made a gradient based on feet.

:o

Wade
03-08-2003, 02:15 AM
Ok last post tonight. You have to have at least one ray trace option on in the render - say shadows and you are up and running.


WWW

roberthurt
03-08-2003, 03:02 AM
Wade,

Thanks so much for your description! It seems I was missing the full combination of double-sided plus the ray trace options to make it work. Now it will be interesting to play with that to see what can be done.

Of course it would be nicer if 7.5b hadn't screwed up lighting settings on my old scenes under Mac OSX, but that's a different thread!