The freezing of battles in wooded areas makes it very difficult to contemplate going into northern Europe unless I want to autoresolve each battle, I usually fight them all, great work on the mod guys but if we could find a fix or work around for the more complicated tree models the game would be so much more playable.

Today, I downloaded 0.5.5 version.

I played test battles with 10k units in vanilla on high-medium settings in 4K without any issue. FPS was between 40 and 60.

With RTR:IS, I began as Rome and attacked Rhegium, there were 3K or less units in the battle, FPS was very low, probably less than 15. I set water and sky to low but when I move camera close to water, I felt FPS was its lowest. When I reduced the resolution scale to 50% (which makes the resolution 1080p I believe), FPS increased to 60 but graphics became terrible blurry of course.

I played another test battle in RTR:IS with only 400 units on battlefield and set the unit details to LOW. FPS was still below 15-20, so I understand it is not the units causing low FPS.

Then I set the grass, terrain and vegetation to LOW and played the last battle again. FPS didn't improve.

Suggestions would be helpful for getting higher FPS.

Another test battle with 5K units, graphics are mostly on medium and resolution at 4K;

I noticed something interesting; when camera is on ground level, FPS is high (40 to 60) no matter where it is or where it is facing. But when camera is above ground level, FPS is between 15 and 20 wherever it is facing except upwards.

I find it interesting because FPS is much higher (close to vanilla) when camera is in the middle of thousands of units where grass and unit details are higher compared to looking battlefield from above.

I just completed a Sparta campaign. I bought extra RAM to try and stop crashes. More stable with 32GB RAM than 16GB. I also found it more likely to crash on high vegetation maps but particularly if you had a more zoomed out view of the battlefield particularly from above. The best chance of getting through a battle without crashing, I found seem to be viewing the battle very close to the army probably so the display has less details to process.

More likely less work for the GPU.

@Apple yes agreed! There was also more of a first person feel to the battle, viewed closed in, although obviously harder to see what was happening, it felt more realistic