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Add info on transparency anti-aliasing. Add tips on tradeoffs between performance, graphics content, and AA
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By default, [[FlightGear]] will not use '''{{Wikipedia|anti-aliasing|noicon=1}}''' during the simulation. This results in incorrect rendering of sharp straight lines and very small objects. In order to correct this, you can apply the anti-aliasing function; however, this will slow down rendering and is not guaranteed to work on all graphics cards. | By default, [[FlightGear]] will not use '''{{Wikipedia|anti-aliasing|noicon=1}}''' during the simulation. This results in incorrect rendering of sharp straight lines and very small objects. In order to correct this, you can apply the anti-aliasing function; however, this will slow down rendering and is not guaranteed to work on all graphics cards. | ||
== | |||
NVIDIA and AMD drivers have an additional option for transparency anti-aliasing that is helpful for use with overlays. | |||
== Examples == | |||
{| | {| | ||
! Anti-aliasing disabled !! Anti-aliasing enabled | ! Anti-aliasing disabled !! Anti-aliasing enabled | ||
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''Thanks to '''[[User:Fredb|fredb]]''' for publishing this information on the [http://forum.flightgear.org/viewtopic.php?f=5&t=10007#p101676 FlightGear forum].'' | ''Thanks to '''[[User:Fredb|fredb]]''' for publishing this information on the [http://forum.flightgear.org/viewtopic.php?f=5&t=10007#p101676 FlightGear forum].'' | ||
== Transparency Anti-aliasing == | |||
Overlays benefit from transparency anti-aliasing. It's most noticeable on overlay grass (High super-sampling transparency anti-aliasing [http://wiki.flightgear.org/images/2/2c/Rotor_downwash_of_the_Aircrane_on_grass%2C_Florence_Airport_%28LIRQ%29%2C_Tuscany%2C_Italy_%28Flightgear_2018.x%29.jpg example]). Transparency anti-aliasing can be enabled in the control panel for NVIDIA and AMD GPUs. However as of March 2020, this is also applied to things like trees. High vegetation density with overlays can cause a bottleneck depending on GPU. Transparency anti-aliasing cantake up a lot of GPU time. This is in addition to overlays being demanding. The Multi-sample (MSAA) option has the best results without too much slowdown. It's recommended. The super-sampling option is slower. If not using overlays transparency anti-aliasing does not make too much of a difference. | |||
== Tips on using anti-aliasing settings == | |||
* Anti-aliasing is more obvious on still screenshots. | |||
* The driver control panels for NVIDIA and AMD support enhancing settings beyond what applications allow. You can use this to override Flightgear, or if you want a GUI interface. | |||
* In motion at high FPS there is an averaging effect that has the same function as anti-aliasing. | |||
* Newer NVIDIA and AMD drivers have the option of "temporal anti-aliasing" that turns down anti-aliasing to free up performance at at high FPS. It's called "Multi-frame sampled AA" in NVIDA control panel. See if your GPU support this. (March 2020) | |||
* At least the NVIDIA control panel on windows supports driver settings overrides for each application by .exe file. If you create a copy of the /bin folder to get a copy of fgfs.exe, and you can set a different set of graphics overrides. This can be useful for example, when you want to take a screenshot of something at high anti-aliasing. You may also need to create a shortcut or equivalent that tells Flightgear where the FG data directory is. | |||
* For monitors with smaller pixel sizes, the decrease in pixel size can function in the same way as increased anti-aliasing. It's similar to the very slow super-sampling variety of anti-aliasing. You may be able to lower anti-aliasing settings. A lower resolution may help performance too. NVIDIA 11xx (and equivalent AMD GPUs) and later series GPUs have integer scaling, so running at half or 2/3rds resolution will no longer be needlessly and slightly blurry. (More info: In recent years (March 2020) there has been a trend of making pixel sizes smaller on LCD displays. For example a 2k (QHD) or 4k (UHD) monitor that is the same size or a little bit bigger than a 1080p (FHD) monitor while containing up-to 4x more pixels.) | |||
=== The trade off between graphics content, FPS, and graphics settings like anti-aliasing === | |||
There's a limited amount of time between each frame for the GPU to do computations. At 30 frames per second (FPS) the time is 1 second/30 FPS = 33ms. At 60 FPS it is 16.7 ms. Flightgear uses this GPU computational time to add realistic light simulation and create content to the scene. How much GPU time is needed for a frame depends on what's being drawn in the current view. For example changing tree density cannot affect FPS over a desert or sea. Whether the lack of GPU time affects FPS depends on where the bottleneck is. If Flightgear is waiting on CPU heavy tasks to finish on a system with an old CPU and a newer GPU, turning up GPU settings further will not reduce FPS. The the bottleneck will most often the GPU on most systems at high graphic settings on most systems when flying over regions which have complex scenes. | |||
Approximately what FPS is acceptable for each task? Ultimately it's a personal thing, to be found out by experimenting. Lower FPS means more time between frames, letting the GPU do more computations. It's been mentioned in the forum that around [https://forum.flightgear.org/viewtopic.php?f=42&t=28681&p=275439#p275439 20-30 FPS] is enough for flying. Less FPS than this might be ok when operating a glass cockpit aircraft where the autopilot handles a lot of flying, and interaction involves pushing buttons. There is a [https://forum.flightgear.org/viewtopic.php?f=37&t=29122&start=15 forum thread] for submitting settings for [[Graphics_card_profiles|different GPUs]] so newcomers will have reasonable starting settings for their GPU. A consistent time between frames (frame spacing) helps deliver a smooth experience even at lower FPS. Sometimes the focus is on FPS when frame spacing is more important. | |||
Using the limited GPU time for anti-aliasing to smooth out jagged lines or get sharp grass at the cost of FPS is a personal tradeoff. My personal view is that turning down graphics content and light simulation just to increase anti-aliasing is not worth it (beyond the basic 4x anti-aliasing needed to display things like trees correctly). | |||
[[Category:FlightGear feature]] | [[Category:FlightGear feature]] | ||