Fog Alpha? Depth?

[Monkeyfarm]

Can someone tell me if the alpha map that can be applied to the fog render effect is supposed to be z-depth aware? That is, will varying degrees of gray allow fog to fall in front or behind objects depending on the alpha's gray value?

Does that make sense?

If it is supposed to be depth aware, then I'm not sure how to do it... I'm trying to create a volumetric light effect with the "god ray" effect that goes in front or behind objects depending on their depth in Z.

Thanks!

[PusGhetty]

Monkeyfarm,
Yes, the fog in zbrush is Zdepth aware... Just highlight the buttons and hold the ctrl button down and you will get an explanation of what the buttons do and how they work.
You can drag the depth sliders to a point in your drawing to set their depth.
Hope this helps some,
Take care,
Michael

[Monkeyfarm]

Sorry PusGetty... That's not what I was asking. I know you can control the overall fog effect's depth.

Here's a diagrom to show what I'm trying to do:

http://www2.zbrushcentral.com/uploaded_from_zbc/200303/user_image-1047672281ilh.jpg

Think of teh fog as well... fog... and the yellow lines are the direction of my light rays. I want the blue ball to essentially cast a shadow on the fog "behind" it (in terms of the light vector) so that everything "past" the blue ball has less obvious fog, or the fog is darker.

If you don't do this then it's not a very convincing effect and it looks like the fog is glowing/giving off it's own light as there are no interactions between the fog and the environment light.

I think I should be able to use the alpha channel to do this, but I'm not sure how...

[PusGhetty]

Oh, my bad, I see... It will take a clever use of alphas to do this methinks.
I think Ken B. did a tutorial on this awhile back but I can't find the thread.
My guess is to just use your artistic license.
Take care,
Michael

[Sarum]

the ken B tutorial about this is on the first zscript page when you open zbrush :) (compositing_sc)