CGTalk - How do i get volumetric lights to produce alpha?

View Full Version : How do i get volumetric lights to produce alpha?

4dartist

11-27-2002, 04:54 PM

I have a shot i'm rendering with objects and volumetric lights. I want the lights to appear on the alpha, but for some reason, just the objects show up in the alpha. for now i have thought of a work around by renderinging just the lights desaturated from color but still white on a black background to make my own alpha. but i would rather just have them produce the alpha with the rest of the objects. Any ideas? Thanks so much guys.

wgreenlee1

11-27-2002, 05:01 PM

I dont think thats logical is it?
Volumetrics are not soilds.

4dartist

11-27-2002, 05:21 PM

What?! No they aren't solids but i need a gradient alpha to be produced from it. Like Glass even tho its almost transparent it will produce a very slight dark gray in the alpha etc. The reason we want an alpha from the lights is for compositing. I need to put renders of the objects and the volume lights infront of my background im making in After Effects. So all i would have to do is when the renders are done.. just plop the renders and their alpha on the top layer in my aftereffects project and tadaaaa! Compositing done. But without getting an alpha for the lights how do i composite?

--- I did what i said on the previous post by rendering the lights as white on black and it semi worked, doesn't look as good but works as an alpha.

Thanks for anyhelp :)~~~

wgreenlee1

11-27-2002, 05:31 PM

Oh wait.
I think there was a plugin for this but cant remember the name .
Heading over to Flay right now.

check this out.It may help.

.Post Alpha (http://www.ats-3d.com/post_Alpha/index.htm)

a2reason

11-27-2002, 05:33 PM

Adjust opacity value from the volumetric options to something other than zero.
Do note that it also affects the appearance of the volumetric effect as it starts to block itself out because of not being 100% transparent.

4dartist

11-27-2002, 05:57 PM

a2reason, ya i don't think I want to change the opacity but thats a good tip tho thanks.

wgreenlee1, Oh MAN~!! Thats what i need but im runing Mac OSX systems here :( and that pluggin is PC only Arg :D ! But thanks for looking that up for me, very kind :) I guess you need a pluggin to do this then hehe i thought maybe it was an option i couldn't find in manuels or interface, but now that i know it has to be a pluggin ill look around more i guess, maybe flay has alternatives than to just that pluggin. Thanks im heading to flay now :).

I think i can, i think i can..

policarpo

11-27-2002, 06:36 PM

hey 4dartist...go ahead and give it a try...post_Alpha2 is an LScript afterall...you may just luck out. :)

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