I have an underwater scene that renders fine on "final" setting at lower resolutions but faults out with an out of memory error or crashes when rendering at higher ones. It is > 200 million polygons. I don't think it's the number of objects though. I believe it is either the fact that I'm using:

1. Displacements or
2. Texture maps

Maybe #2? Do texture maps eat up more RAM at higher resolution renders? I could take this out and use procedural no problem. The maps aren't critical to the scene, especially the foreground terrain which is mostly covered by seaweed.

Displacement mapping. It's virtually useless on a 32 bit platform. Even though 32bit can have 4 gigabytes of RAM, Windows XP 32 is only able to allocate 1,2gigabyte per allocation. Exceeding that limit, the application will crash. Forget about the 3gigabyte switch, that is but a dream.

I've had a displacement of pebbles for a couple of hundred meters (quality +2) in Vue7 x64 with 4 gigabyte of RAM and the commit charge spiked to 7000 (extending the page file) in a matter of seconds.

Attached Link: Displacements&crashes

Okay so I tested it by process of elimination.  Displacement is causing NO problem on my system.  But by eliminating the bitmapped images on the terrains, the render went from not working at all (or crashing after 20%) to rendering the image in 20 min at 1440 X 900.  My CPU meter showed the RAM never got much above 40% and the CPU useage stayed at 100% for each of the 4 cores.  I did reduce the quality of the displacement to -3 (which is fine for what I'm doing).  I may re-render with  the other spheres in displacement (since the bumpmapping is leaving some bad moire patterns).  I also need to make my cones holding the fish ecosystem COMPLETELY unseen or delete them while keeping the fish.