When you start to work it out, you realise how much time it takes for a render, I think everybody who starts in CG dreams of making a movie or a short till they realise the number of machine-hours it takes.
Weta has a massive render farm - it had about 40,000 cpus for Avatar and that was in 2009 - they've got to have more now. Given the new Avatars are supposed to be 3d (stereo frames) at 60 frames per second, they'll need it
And each frame will be combined from multiple render layers...
Pixar also has a massive farm - but they usually render the whole frame in one go, without layering, each one of their frames can take 1-2 days to render.
If you haven't seen it - check out "Fifty Percent Grey" by RuairĂ Robinson (
https://www.youtube.com/watch?v=s9-MoYrXP0o ) - who did it on his own with one or two machines. I'm sure that's why he made such a minimalist short, and it probably took forever to render that 3 mins, but the idea worked for him and he was nominated for an Oscar.
Pixel Plow are very cost-effective, but let's say you have a 1 min 30 sec animation at 24 fps that renders at 30 mins a frame on a 16 core 3.6ghz machine, that's gonna cost you $400+ and if you're planning to do this on a regular basis, that's almost throwing money away.
When I did my Terragen animation - it was a one-off and I set out to do it with a budget of $250 ( I went $20 over
) but if I was to do this regularly I'd do as Hannes suggested and get another machine. Just trawl around the net and find an affordable refurb machine ( get enough RAM though ) stick it in the garage and let it spit out frames 24/7
p.s Terragen is almost the worst-case scenario as you're generally rendering an entire frame of CG and layering isn't really practical in most cases. In the case of my short, I decided that as I wasn't doing anything spectacular with the sky, I didn't render clouds (I comped in a skydome) - that probably halved my render times.