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Setting Up X-Plane for Best Performance

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X-Plane users tend to notice either that the simulator runs extremely fast, giving them 100 frames per second (fps), or that it is dismally slow, topping out at 20 fps. At identical rendering settings, this is due almost entirely to the hardware in the computer.

A number of settings in the simulator can be tweaked in order to maximize performance, but it is important first to understand why X-Plane performs very well on one computer, but not so well on another.

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Factors Affecting X-Plane's Performance

Some people’s computers today have a 500 MHz Pentium III processor with 128 MB of RAM and 8 MB of VRAM (perhaps an 8 year old system), while have quad-core 3000 MHz processors, 4096 MB of RAM, and 512 MB of VRAM (perhaps only one year old). There is more than a 6x difference in speed between those two setups, since the RAM speed, bus speed, video card speed, and many other things also influence the computer’s performance.

Many people do not understand what determines a computer’s performance. The three biggest factors are the amount of RAM in the system, the speed of the CPU, and the speed of the graphics card. A fourth factor, which determines a system’s ability to display high quality video textures, is the amount of RAM on the video card (called VRAM).

Coming up short in any of the above categories will create a “bottleneck” in system performance, limiting the ability of the rest of the components.

For instance, using higher quality textures than can be stored in VRAM will slow X-Plane significantly (see Chapter 3, Section III, Part B, Subsection i for more information on VRAM and textures), regardless of any other factors.

Conversely, even if the system’s video card has 2 GB (that is, 2048 MB) of VRAM and X-Plane is running at a low screen and texture resolution (eliminating any RAM problems), if the computer’s CPU or video card are too slow, then X-Plane’s performance will be poor.

Optimizing X-Plane's Performance

The following procedure will allow the user to optimize X-Plane’s performance for his or her computer, regardless of the power of that computer or any limitations it may have.

Displaying the Frame Rate

Before we begin, we will need to be able to tell how fast X-Plane is running on the computer. To do this, launch X-Plane and:

1. Move your mouse to the top of the screen (causing the menu to appear) and click Settings, then Data Input & Output, as seen in the screenshot below.
Image:Data_in_and_out_-_selecting_it.png
2. Check the far right box next to frame rate, as in the image below. This will cause X-Plane to display the current frame rate in the upper left of the screen during flight.
Image:Data_in_and_out_-_display_frame_rate_in_sim.png
3. Close the Data Input & Output window (either with one of the Xs in the corners of the window or with the Enter key on the keyboard). You should now see how fast the simulation is running, in the freq / sec output on the far left. This is the current frame rate, given in frames per second (fps). For instance, in the image below, the computer is putting out about 79 frames per second.
Image:Data_in_and_out_-_display_frame_rate_result.png
Note that the frame rate will change depending on what is happening in the simulation. It is not uncommon for a computer to output 50 fps while sitting on an empty runway, but drop down to, say, 35 fps when rendering lots of buildings, other aircraft, etc.
Refer to the following to determine the significance of this number.
  • 15 fps is terrible and barely adequate to run the simulator.
  • 30 to 50 fps is the ideal range. Higher frame rates indicate the computer isn’t rendering with as much detail as it could. Studies have shown that starting at about 50 frames per second, users’ subconscious minds forget that they are looking at a simulator and begin thinking they are actually flying.
  • 100 fps is excessively high and indicates that the system has plenty of capacity to draw more buildings, clouds, and other objects.

Modifying Visibility and Cloud Rendering

If the simulator’s frame rate isn’t as high you would like, you can raise it by doing the following:

1. Bring down the menu as above and click Environment, then Weather, as seen below.
Image:Selecting_weather_from_the_menu.png
2. Using the upper, mid, and lower drop-down menus (found in the upper left of the screen), set the cloud types to clear or cu overcast for max frame rate. For a good frame rate, set them to hi cirrus or lo stratus. Cu scattered or cu broken take a ton of computing power to display.
Image:Set_clouds_to_clear_or_cu_overcast.png
3. Set the visibility (found on the left side, near the middle of the screen, seen below) to about five miles or so. Higher visibility takes more computing power because the computer has to calculate what the world looks like for a much larger area.
Image:5_mi_vis.png

With that done, close that screen and check the frame rate again. To improve it even more, continue on to modifying the texture resolution.

Changing Texture Resolution for Best Performance

1. Make the menu bar appear as in the above processes and click Settings, then click Rendering Options, as seen below.
Image:Selecting.png
2. The texture resolution drop-down menu (shown below) determines how much video RAM (VRAM) the computer will use. If your graphics card has plenty of VRAM, you can set it as high as you want with no loss in frame rate, but as soon as the texture resolution requires more VRAM than the graphics card has, the simulator’s frame rate will plummet.
Image:Texture_res.png
3. To determine how much VRAM is being used at the current settings, look at the very bottom of this window. The last line reads “Total size of all loaded textures at current settings: xx.xx meg.” For instance, in the following image, the textures loaded are using 75.44 MB of VRAM.
Image:Total_size_of_all_loaded_textures.png
While it is in some cases possible to load more textures than can be stored in VRAM with a performance hit (as not all textures will be used all the time), the size of the loaded textures should not be significantly greater than the VRAM on the system’s video card.
4. Lower the texture resolution if the current settings require much more VRAM than your video card has.

Note: After changing the texture resolution, X-Plane must be restarted for the change to take effect. We recommend putting the texture resolution on its lowest setting, exiting the sim, restarting it, and noting the frame rate. From there, raise the texture detail up one level and repeat until the frame rate decreases. This is the point at which all of the video card’s RAM is being used. Back the texture resolution off to one level lower than where the decrease was noted and restart X-Plane one more time.

Setting Screen Resolution for Best Performance

Next, look at the screen res (resolution) setting on the Rendering Options screen, shown in the image below.

Image:Screen_res.png

Higher resolutions use up some extra VRAM, but not much. The screen resolution is the size of the image that X-Plane is drawing, in pixel width by pixel height. A user might have a large, wide monitor but that does not mean that drawing a large, wide screen must be more difficult for X-Plane. A relatively low number of pixels can be drawn on that screen by setting the resolution in the operating system accordingly.

Windows XP users can change their resolution by doing the following:

1. Right click on the Desktop and click Properties.
2. In the window that opens, click the Settings tab.
3. Drag the Screen Resolution slider to the desired resolution.

In Vista:

1. Right click on the Desktop and choose Personalize.
2. Click Display Settings.
3. Drag the resolution slider to the desired resolution.

In Windows 7:

1. Right click on the Desktop and click Screen Resolution.
2. Click on the Resolution drop-down box and drag the slider to the desired resolution.

Mac users can do the same by doing the following:

1. Open the System Preferences from either the dock or the Apple menu.
2. Open Displays menu and click on the Display tab.
3. Select the desired resolution under “Resolutions.”

Note that drawing a large screen with few pixels will look 'grainier' than drawing a smaller screen with more pixels—assuming that the monitor is viewed from the same distance in each case. Drawing more detail (with a higher screen resolution) uses up some of the video card’s processing power, but not too much. In most cases the biggest bottleneck when using a higher resolution is the processor, as it must calculate the view for a larger, more detailed area.

Play with the screen resolution a bit and set the resolution as you see fit. Many computers will run best at 1024x768. Remember that X-Plane will have to be shut down and restarted for the changes to take effect.

Optimizing Other Rendering Options

These are the really critical options-—the all-important number of objects and number of roads settings, highlighted in the image below.

Image:Num_of_objects_and_roads.png

These have a huge impact on frame-rate. Set these to none for the most speed, then restart X-Plane for the changes to take effect. Check the frame rate, bring both settings up one level, and repeat, restarting the sim each time to see how performance is affected. Setting these options to higher levels will look much nicer but will negatively impact the X-Plane’s frame rate.

Another important factor for X-Planes performance is the "world detail distance" setting, right above the formerly discussed dialogue. This setting determines how far away from your aircraft 3D objects will be rendered respectively visible. Given the fact that the surface of the X-Plane world is a 2 dimensional body - doubling the detail distance, will cause X-Plane to draw 4x times! as many objects. Because from the aircraft point of view the number of objects will grow in all four directions equally. Once again this is of course a huge impact on the frames, so in order to optimize frames try lowering these settings as well.

Above this you will find the settings for "forest density" and yes, you guessed it, depending on your settings in "world detail distance", higher settings will once again increase the load on your graphics card in a squared manner. Also here lower settings are the key to more performance.

"Airport detail" to the right is a very interesting rendering option, higher values will draw nice 3d runway lighting and other pretty details like actual physical 3D center line lights and runway edge lights instead of just lighting spots without bodies. Giving the airport environment a very nice authentic look. But since these are practically only visible when taxiing around on the ground, you might find it easy to abandon this option. And yes, lowering these settings will of course also improve performance.

"Traffic density" is a setting that we can disregard if we did not render any roads before. Nevertheless, remember the more pretty 3D cars we have driving around X-Planes highways, the higher the demand on our rendering capabilities. If you do not plan do simulate highway patrol ops turn this option down or off to achieve more frames.

Most of the different boxes in the PERFORMANCE RENDERING OPTIONS section of this window do not impact the frame rate much, with the exception of use Pixel Shaders for amazing fog and water effects (highlighted in the following image). Therefore, set these up as desired, but make sure use Pixel Shaders is unchecked for greatest speed.

Image:Use_pix_shaders.png

Changing the Number of Other Aircraft

The final setting that really impacts the simulators frame rate is the number of other airplanes. Access this by moving the mouse to the top of the screen, clicking Aircraft, then selecting Aircraft and Situations, as seen below.

Image:Select_aircraft_and_sits.png

The number of aircraft setting (found on the left of the screen, about halfway down, highlighted in the screenshot below) should be set to one (yours) for maximum speed.

Image:Num_of_aircraft.png

Setting this number higher will cause X-Plane to use artificial intelligence (AI) to fly any specified number of other aircraft in the sky. Note that there is no logic to determine what type of aircraft to place or where (for example, a hot air balloon may be seen flying around New York City).

With that done, it's time to fly!

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