I'll try to keep this short and concise (I timed out and don't want to try to rewrite everything.) I got Terragen 3 yesterday. I have a fairly outdated system (Intel Core 2 Duo E4500 processor running at 2.20GHz, with 2GB DDR RAM - two sticks of 1GB each.) Other basic details can be found in the second screenshot. I also run on 32-bit Windows 7, though I've heard that 64-bit is better. My expectations for system performance were pretty low to begin with. First thing I did, I made a basic mountain with a lowland in the horizon, midday, virtually no special effects or anything, no water, no clouds... and I rendered it at 1280x800 pixels, and after an hour or two, it popped out clean, quite realistic, and even astonished my brother (who majored in graphic design and loves 3D landscapes.) Admittedly, he might've been more astonished that I made it on this computer than anything else. Still, came out well, and it didn't even take as long as I expected.
Do note that I had worked a little with Terragen Classic before graduating to Terragen 3 (Free Version.) I tried adding water to that same first landscape, as well as some sun and atmosphere effects, tried rendering it, and I got the 'Not Responding' at the top of all the windows. I tried waiting it out, and after several hours of no response, I closed it and lost all progress. I started anew, did similar things, and it crashed. Turned out that it kept popping up with 'Not Responding' because I raised the memory subdiv cache from 400 to 800. I lowered it to 600, got the same result, so then I lowered it back to 400. Well, no more 'Not Responding' messages at the top of each window! However, there are still some concerns...
I made a new picture, one medium sized island in the middle of an ocean, sunset, some cloud coverage (volumetric cumulus and 2D cirrus), the clouds are set to max quality (my mistake, as I've read this wasn't necessary), have max reflectivity, almost perfectly still waters, a modest array of shaders, atmospheric effects, and lighting effects. Resolution is 1280x800 like the first render, the subdiv cache is back to 400MB, it's set to use 1-2 threads (maximum one thread per processor core), and many of the qualities are set highest or normal. Clouds are set to be 'Optimised.' The render preview was a burden on the CPU and memory, frequently maxing them out, and taking upwards of 30 minutes to come up to 80 quality. The terrain geometry is set to polygons. With how tough the render preview was on the system, I expected the final render to take quite some time and stress both the CPU and memory.
Well, over 15 hours into the render, now, and it looks the exact same as it did only 10 minutes in. Still lots of orange, sunset colored dots at the top... and pitch black rectangular patches at the bottom. I've paused and unpaused multiple times with no chance... The timer just continued from where it left off. Everything on the computer otherwise seems to be running smoothly. The processor seems to rarely get above 10%, usually hanging around 0%, usage when no one is actively using the computer, even if other programs are going like Vuze downloading a torrent, or Firefox just left on, or some other miscellaneous program going. The memory usage rarely goes above 60% usage, even when the computer is being actively used by someone. Perhaps more details could be discovered when looking over the first two screenshots I've attached. I'm also attaching a third screenshot showing the render advanced settings. Nothing special, really.
So, please, if someone has even an inkling of what might be going on, I would appreciate the feedback. I just don't understand why Terragen doesn't seem to be using hardly any CPU or memory, and doesn't seem to be making any progress, and yet nothing else seems amiss!
Side Note: I did get two error messages, "Unknown error occurred in a render thread," but these seem pretty generic and easy to ignore. I got four or five of them on the first render I mentioned that came out just fine. No warnings or further errors have come up since the very, very beginning of the render.