I’ve noticed for a while that when I exit and re-enter VR mode, my fps changes considerably. Recently, I was getting about 20fps, I exited&re-entered and got single figures(!), exited&re-enetered again and achieved about 30fps. All of these were stable, i.e. didn’t change if I waited.
FS2024 now runs only in DX12 mode, and I know from the FS2020 experience that DX12 is much more demanding of VRAM than DX11 (which by design is not available in FS2024). I am using a GTX1080Ti, and although it’s an old card it has actually got 11GB VRAM, compared with the 8GB of many more modern cards. During the Q&A session, Seb did comment that many users are suffering with the VRAM, but in the FS2024 bugs list the fps/VRAM topic is unfortunately dismissed with the status of “Hardware Limitation”, rather than being “under investigation”.
I thought it likely the strange behaviour I was seeing was down to the VRAM being overloaded, and the sim attempting to make more space available in the VRAM or shared memory.
So I ran FS2024 through normal start-up and flight, at each stage making a note of how much VRAM had been used out of the 11GB available. This is a summary of the major points at which the VRAM usage changed:
(NB for the first part of the list I was in 2D)
0.4GB Before start-up
3.0GB After the trailer
3.0GB After selecting “Start”, then “Free Flight”
3.1GB After setting up a flight (from Orlando in the Albatross) using the EFB
8.1GB After clicking “Start Flight”
7.1GB After clicking “Ready to Fly”
8.2GB After looking around through the side windows
8.3GB About 30 seconds into the flight
7.7GB A few seconds after switching to the chase view
7.9GB Back in the cockpit
8.2GB After flying at roof-top level over a town
7.6GB After gaining a few thousand feet of altitude
7.2GB After pausing and switching the sim to “windowed” mode
7.2GB After starting my headset (Quest 2)
9.0GB After entering Desktop mode on the headset
8.5GB After entering VR mode in the sim
7.8GB After a few seconds
8.3GB After flying at rooftop level
8.2GB After ending flight
6.7GB After setting up new flight (Heathrow in the Longitude)
10.4 GB After exiting VR into 2D Mode
9.8GB After takeoff (back in VR Mode)
At this point, I tried to exit VR, but the system froze permanently.
From these results, it is obvious why anyone with 8GB of VRAM is having a problem, as most of the flight my system was using over 8GB. Even with my 11GB, my fps was suffering at times when the usage was close to this limit. The fps certainly seems to take a hit when the system needs to start shuffling memory with VRAM getting full.
Another conclusion is that the usage of VRAM is constantly rising throughout the process. The most interesting change though was when I swapped out of VR into 2D. This seemed to use up a significant amount of memory, which was not recovered returning to VR.
This made me wonder if my method of starting a flight was a problem. Due to the occasional problem with the “Ready to Fly” button not appearing in VR, I normally start a flight in 2D, then swap into 3d after I’d clicked on this button. This was probably loading up the VRAM with 2D data which may not be necessary for VR.
I have the 2D settings on my system set to Ultra. I have just watched a YT video which pointed out that the “texture resolution” setting has a major impact on performance. Assuming this was likely to be affecting VRAM before I entered VR mode, I changed this (2D ) setting to “medium”. I already had the VR setting set at this level.
I also changed the point at which I enter VR, assuming I’m not then cluttering up the system with unnecessary 2D data, only useful VR data. I now switch to VR immediately after I click on the “Start” button at the end of the trailer.
This has improved my performance, so that I am now achieving over 30fps consistently - before I sometimes reached above 30, but was often in the teens, with stuttering to match. Looking at my VRAM usage, it is now between 6 and 8GB, in various aircraft and from various airports.
I know this won’t be of help to many people, but I would encourage everyone to look at their VRAM usage during a flight, and modify their settings and their method of using the sim if they are constantly close to their VRAM limit.