Long render times

[godshall]

I've been trying to get a high res, single frame render from a scene I've been building. I've started and stopped numerous times trying different settings to get a reasonable render time but so far, no luck. I've searched the forum for setting recommendations and read/tried everything I can regarding min/max threads, number of cores to utilize, "size of subdiv cache..." settings, everything I can think of and for all my testing haven't found anything that rendered faster than the defaults in the advanced section of the render tab. Some of these renders I let go over 60-70 hours with no more than 5% of pixels rendered. I've never had an error message so it's not that the renders are failing, I would just like them to be done in something less than 100 hrs!

As for quality my pixel dimensions are 3000x1850, detail of 0.6, AA 4, GI detail 1 quality 1, Atmo samples 32. Most of which are less than half of what I started testing at. My Machine is a Mac Pro with 2 x 3 GHz quad core Intel Xeon processors and 9 GB's of ram, OS 10.5. I've rendered other higher resolution frames with no problem so maybe this scene is just too complex?

I've attached a .tgd if anyone wants to take a look. Maybe I've overlooked some obvious unnecessary render option, or just never found the right thread settings? Thanks in advance if anyone has any insight to offer, I really appreciate it.

[gregsandor]

How long does it take to render at one third the size 3000x1850?

[N810]

"3000x1850, detail of 0.6, AA 4, GI detail 1 quality 1, Atmo samples 32."

I think I just found out why your renders take so long... 

[FrankB]

I've rendered your scene at 1/25 of your target solution on my macbook pro. It took 6 minutes to render IF I DONT generate your heightfield. So it would take at least 150 minutes if I render this in your target resolution - maybe twice that, but that still would not be more than 5 hours.

*however* I have realized that if our heightfield is generated, the camera is under the planet surface. Some of the lights are also under the surface. This combination is giving you these insane render times.
So you have to correct your camera altitude and place it atop the heightfield and your mac pro will like you again

regards,
Frank

[godshall]

"*however* I have realized that if our heightfield is generated, the camera is under the planet surface. Some of the lights are also under the surface. This combination is giving you these insane render times.
So you have to correct your camera altitude and place it atop the heightfield and your mac pro will like you again "

I forgot there's an image map shader needed to create the terrain that's why the lights and camera appear to be undergound. There's a powerfractal that displaces 50 (metres?/feet?/units?...) downward to create a crack that splits and disappears into the horizon. Here's a link to the image map shader if anyone wants to take another look http://www.mediafire.com/file/ajmyz11tjmm/crack-2-low.jpg. It would need to be plugged into "Power Fractal shader v3 01" (I know, I need to name things better). The lights are supposed to be spilling out of the crack and ideally, making "godrays". After  testing the godrays I decided it would be easier to do in post.

Thanks again for taking a look.

[godshall]

I realized it was the shadow calculations from all the lights that was slowing it down. When leaving all of the lights on but turning off "cast shadows" my test rendered in 1/3 of the time it took with shadows on.