Volumetric Lights + GI = Very Long Render!

[Dreamerrr]

Hi,

I'm writing to find out if there anything I can do to quicken the rendering of volumetric lights in VRAY when GI is on? The first file I rendered with GI off was around 6min 45 secs, and the second (same file file just with GI turned on) was 1 HOUR 45 minutes!!!

There must be some way to speed it up. Is there some way that I can render the scene and then the volumetrics seperately and then add them in post production? Any ideas?

Thanks...

Ciao
Bryan

[percydaman]

yes I do it all the time. just give your scene an all back material and render it out with scanline. Comp it in photoshop.

Example:

[Long John]

great example.

[percydaman]

thanks.

[Dreamerrr]

I was thinking about something like that, but I'm not doing a still image, I'm trying an animation, and for everyone that doesn't have a render farm the size of ILM , an Hour and 45 minutes odd per frame is just too long (and I've just added a nice steam after burn effect! ).

Any ideas for the animation?

Thanks,

Bryan

PS I remember seeing ILM put together scenes using multiple layers, like one was the background, the second was the modeling, the third was the volume effects etc,. etc,. Any idea how to do that?

[RErender]

It is done with compositing programs much like with a single image in photoshop but on the whole animation at one time, most of them cost $1000 or more, here is a pretty good list of the major ones.
http://bakhter.com/html/3d/3d_compositing.html


FilmFX64 at $99 can get the job done for most compositing it supports a few blending modes and alpha http://www.satoripaint.com/

[percydaman]

you can even do it with photoshop. render out the volume pass to tga files and peform your composite in photoshop and save it as an action. use it to batch render your new files.

Heck couldn't you even do it with max's video post?

[Dreamerrr]

Okay, thanks for the replys... now I've got a little bit of a stupid question, so prepare yourself...

If I was to make every material in the scene black (or just make a black material and apply it to all the objects), wouldn't those objects in the scene affect the TGA's alpha even though they are black. And if that is the case, then how do I get an alpha with just the volumetrics in, cuz if I had all the objects hidden, then there would be no shadows?

Hmmm... just thinking out loud, but maybe in object's parameters, tick off visible to camera, but keep cast shadows? Hmmm...

Thanks chaps,

Ciao
Bryan

[percydaman]

actually now that I think about it, I think I gave everything a matte/shadow object and fiddled with the settings until it was right but I dont recall for certain.

[cocolas]

yeah if you have objects behind/in front of the volumetrics light you do need to give them a matte/shadow mat when rendering w/ scanline....and save as a tga


paul.