I suggest you run 2 instances of TG2 at the same time.
Configure each instance to use 1 thread minimum and 4 threads max. Volker mentioned going beyond 3 threads isn't giving much better performance, so you might consider setting it to 3 max.
Usually a 100Mb cache size per thread is sufficient. So using 1600Mb for 4 threads is a bit of overkill.
I attached a .tgd where I changed some settings. It reduced the rendertime of a crop from 1m55s to 1m18s = -32%. Given the size of your project it's a significant gain I'd say.
I'll explain briefly what I changed:
- Changed cache size to 100Mb/thread.
- Changed render bucket size to 128x128. Especially for water at the bottom this works nicely, as you don't have to wait ages for the last bucket to finish, since it's 4 times smaller.
- Changed GI from 2/2 to 1/3. Your scene doesn't have challenging shadows which require high GI settings.
- Increased AA to 4. Why? See next point.
- Enabled ray traced atmosphere. The quality of raytraced rendered elements in TG2 depend on the AA setting. AA also works better with settings of power of 2, though not that important here. Raytracing atmosphere often allows for less samples needed to get a clean result, compared to the normal rasterized renderer.
- Reduced samples in clouds. Especially your cumulus, which had so many samples that it resulted in a quality of 3.x...that's very high!
All in all that resulted in a similar result, maybe even slightly better, and 32% rendertime reduction.
A couple of notes:
You disabled "do raytraced shadows" in the rendernode. By default this should be enabled, as it generates accurate shadows on your surfaces. Now the shadows of the ripples on the water will not be accurate. You'll only get darker shades on the faces facing away from the sun, but the water-geometry itself will not cast any shadows anymore.
Volker mentioned mis-matched lighting when rendering in crops. A 100% proof way of avoiding this is to use a fill light setup instead of GI. However, this will especially greatly affect the rendered result of clouds.
You could use the "GI prepass-padding" option in the Advanced tab of the rendernode. Set it to 0.2, for example, and it will calculate the GI outside the camera frustum at a size 20% of your image size. So if your image is 3000x3000 pixels then the extra GI will be calculated 0.2 x 3000 = 600 pixels extra on each side of your image.
This way it is more likely that adjacent crops have more matched lighting. You would need to play with the value though.
A drawback is that it increases rendertime.
I hope this all helps.
Cheers,
Martin
