Performance and Memory

How do I display frame rate?

From the main menu bar, select Settings -> Data Output. (V7 and up, click the Output tab if it's not already selected.) In the menu that comes up, look for "Frame rate / time ratio" in the upper left. Click the right hand button next to it.

When I switch to external view my frame rate tanks

The plane probably has an externally visible cockpit object. Adding it to the rendering load has overloaded your video card. To get your frame rate back, either reduce your rendering load by turning off features or switching to 16 bit mode, or open the plane in PlaneMaker and remove the cockpit object. For a detailed explanation, see the video card FAQ page.

How can I improve frame rate in X-Plane?

X-Plane's frame rate is mostly determined by how much work it has to do to render your current view. The following factors affect frame rate:

The following factors do not affect frame rate:

I have a really powerful video card, and I still get frame rate warnings and fog

You're probably running out of cpu power, rather than rendering power in the video card. This is most likely to happen with high object density (lots of buildings and trees, streets, taxiways, etc.) For details, seet the video card FAQ page.

How do X-Plane's resolution settings affect VRAM and frame rate?

Thanks to Ben Supnik:

In X-Plane every texture is downsampled from its on disk size based on the resolution settings:

Please note that under normal conditions, terrain textures are always reduced in half one more time than all others! The only exception is extreme res, where everything is seen as it is on disk.

X-Plane uses linear interpolation to 'smooth' textures as they are downsampled; this can blur fine lines, etc.

All textures must be a power of 2 on each side, e.g. 1024, 512, 256 pixels, etc. The max texture size is 1024, the min is 4.

The masks and terrain textures are stored separately, so you can reduce the masks used to create texture borders and save VRAM without reducing the textures themselves. This is already done to a limited extent; most 256x256 textures have 128x128 masks. Terrain textures are stored in 24-bit RGB, but alphas are stored in 8-bit alpha, so terrain takes up 3 x the VRAM per square pixel as masks.

X-Plane's terrain-drawing framerate is partly a function of the number of types of unique terrain (as defined by distinct bitmap, not distinct land use!!!) and even more so by the number of quads that have multiple terrains visible at once. So by using the same bitmap for more kinds of similar terrain, you can both save VRAM and improve framerate. For example, if you use one forest bitmap for all of the forests defined in the land_use.txt file, the sim will get faster and use less VRAM (since only one bitmap is loaded, and borders between kinds of forests become continuous forest).

You can artificially influence the ratio of VRAM used for objects vs. scenery by resizing the terrain bitmaps to be smaller and then running the sim at a higher resolution.

Saving VRAM will not improve frame rate beyond a certain point; once everything is in VRAM, frame rate is limited by CPU, polygon and fill rate of the graphics card. For 8 MB cards VRAM is very important, but for a 16 MB card running at 'high' resolution, you're probably well within the card's VRAM capacity. [These are old numbers. 16MB is currently the absolute minimum for X-Plane, and 64MB can be considered "comfortable".]

How can I get acceptable frame rate in V7-8 on an old machine?

There a couple of serious frame rate killers in X-Plane V7+, compared to earlier versions: 3D clouds, cloud shadows, and new runway textures. You can get frame rates comparable to or better than V6 by doing the following:

I have noticed that when I am running X-Plane every once in a while X-Plane freezes for a while.

X-Plane is loading new scenery. The scenery is organized into one degree squares. The Low Enroute window contains a 3x2 degree patch of the terrain and X-Plane keeps you more or less in the center of that window by loading whole degrees of scenery as you move.

(The remaining discussion only applies to X-Plane versions 6.x and earlier. In X-Plane version 7 and later all scenery is on the HD.)

If you want to speed this up, have a look in the DATA folder on the X-Plane CD. You'll see folders named something like +40-080. Each folder covers a 10x10 degree square and the name is the latitude and longitude of the lower right corner of the square. So for example +40-080 covers the northeastern USA and southern Quebec. Simply copy the folders for the areas you fly in to your X-Plane folder on your hard drive, into Resources\Earth Nav Data.

Note!! The X-Plane install includes the +30-120 and +30-130 folders to cover parts of the US west coast. These folders are not fully populated; the remaining scenery files are on the CD. DO NOT simply copy the complete +30-120 and +30-130 folders from the CD to the HD. A couple of the scenery files on the CD are wierd and are not recognized by X-Plane. The folders in the install contain good copies. Only copy files from the CD that are not yet on the HD.

I copied all the scenery to the hard drive and X-Plane still pauses occasionally.

Scenery loads still take time even if all the scenery is on the HD. There's a lot more than just reading the scenery in; all the scenery textures have to scaled according to the rendering options. The more recent versions of X-Plane make multiple copies of the textures at varying precomputed resolutions to optimize graphics performance.

On the Macintosh the CD may still spin even though you have all the scenery on the HD. The problem is the MacOS file system, which occasionally hits the CD for file metadata even though the app is not making any explicit references to the CD. You can make the pauses go away by switching back to the Finder after X-Plane has started up and ejecting the CD.

I'm getting a lot of short pauses running X-Plane

There may be other applications or system processes running that are taking up cpu time.

As of V8.32, the pauses may be caused by incremental scenery loading, if "background loading" is disabled. Here's what Ben has to say on the subject:

Regarding scenery pauses:

The bad news: the end result is lots of small pauses. NOT what people wanted but necessary for implementation reasons.

The good news: at least on my 1.8 ghz G5 the stuttering is very slight with appropriate rendering settings (NOT "insane") and they don't happen all the time.

All of this applies only IF you disable background loading. You should only disable background loading if you get thread failures. (You will know this because the alert box in xp830b11 will say "turn off bkgnd loading".

Anyway, in the fallback mode there will be a series of stutters 4 times per DSF file, roughly (so about every 25 km). The number of stutters and length is a function of the scenery "none" there are none, at default they are few and small and at "insane" they are
numerous and large. So if you have to kick into non-threaded mode, I recommend turning the 3-d down.

More info in my current blog entry:

I am still working on debugging this, so I hope that more and more users can run with background loading in 830, 840, 850. It is my speculation that the thread problems happen on heavily overloaded machines, but since Austin and I have never seen this, we just don't know.

When I try to run X-Plane on my OS8/9 Macintosh, it comes part way up and then hangs.

You're probably running out of memory. Check the memory requirements for your current version. You can turn on virtual memory and run X-Plane in real memory that's about 2/3 the stated requirement if you're willing to put up with pauses in view switches, menus, scenery loads, etc.

Other causes of crashing on startup are extension conflicts and OpenGL versions. OpenGL 1.1.3 has been reported to be troublesome. Upgrade to OpenGL 1.2.1.

In general, it's a good idea to keep your extension set to a minimum when running X-Plane, both to conserve memory and to minimize conflicts and pauses.

Does adding memory help X-Plane on Mac OS8/9?

(This discussion applies to X-Plane declared memory size on Mac OS 8/9.)

Only if it doesn't run. Adding more memory than needed will not increase frame rate. X-Plane keeps a considerable amount of data in memory - airports, navaids, textures, etc. If it runs out of memory it usually hangs. The memory size X-Plane ships with is adequate for normal use. If you use custom scenery with a lot of custom textures, you may need to increase X-Plane's memory size.

Does adding RAM help on other systems?

On more modern operating systems like Mac OSX and Windows 2000 and XP, X-Plane will page fault if you don't have enough RAM. In extreme cases this will affect your frame rate. However, you can get away with running X-Plane in less than the required memory (say, 256MB on a PC instead of the required 512MB for X-Plane V7.x) if you're willing to tolerate a slower startup and occasional delays when you switch views or bring up a map. As long as the flight model code, and rendering code and data for the current view fit in RAM you're OK. Note with X-Plane V8.x minimum RAM requirement is 512MB; you'll get nowhere with less.
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