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

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:

• Visibility (in Settings -> Weather Atmosphere). The farther you can see, the more terrain and stuff X-Plane needs to render.
• Field of view (in Settings -> Rendering Options). Same deal: a wider field of view lets you see more and makes X-Plane do more work.
• Clouds (in Settings -> Weather Atmosphere). The scattered and broken clouds in V6 have a modest frame rate cost. The V7+ 3D clouds (what you get with scattered or broken clouds) are build up out of a great many texture objects and cause a major frame rate hit.
• Cloud shadows and reflections (V7+) have a substantial frame rate cost.
• Textured lights have a modest frame rate cost.
• Resolution (in Settings -> Rendering Options). Higher resolution means more data for your graphics card to handle for each frame. This covers both screen size and texture detail. Note higher resolution also requires more VRAM in your graphics card. When you're close to running out of VRAM there is an abrupt drop in frame rate, typically going to zero in short order.
• Objects (in Settings -> Rendering Options). All the scenery and eye candy goodies cost frame rate. This means trees, air traffic, objects, plane exterior, and forest fires. Autogen and object density and visibility distance translate directly into rendering load.
• Instrument panel. The glass cockpit instruments, especially the EFIS map, cost frame rate.
• 3D panels substantially increase the graphics load and consume more VRAM. because of implementation issues they cause an especially bad hit if you're running in 16 bit mode.
• Same goes for externally visible cockpit objects.
• Location. For better frame rate, stay away from areas with lots of buildings and complex airports. LAX is a good example.

The following factors do not affect frame rate:

• Custom Scenery Textures. Lots of terrain textures in custom scenery require more memory but don't affect frame rate.
• Memory (except for extreme cases). In Mac OS8/9, X-Plane either has enough memory or it doesn't. In the latter case, it hangs. In paging operating systems (Windows, Mac OSX) you had better have enough memory for the basic flight mode. If you don't your frame rate will go through the floor (and OSX will give you the spinning beachball). Marginal memory will cause pauses in changes in view and when you bring up menus, and will substantially slow down loading of aircraft and scenery.

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

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:

• For object, aircraft, autogen, and most non-special-case non-terrain textures, the size of the texture is divided by two for each resolution size below "very high". (So high = divide by two, normal = divide by four, etc.)
• For terrain textures, the textures size is divided by two for every size below "extreme".
• Some textures such as the aircraft panel markings (both blend and test) and the main UI texture as well as a few others are never made smaller because they would not function properly.

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:

• Don't use scattered or broken clouds (Settings-> Weather-> Atmosphere). Use Haze Layer or High Cirrus instead.
• Turn off cloud shadows in the Settings-> Rendering Options menu.
  
• Reduce texture resolution in the Settings-> Rendering Options menu.
  
• Use the generation 7 scenery if you're running V8 (see the Scenery page).
• Use an aircraft with a simple panel. Each instrument consumes VRAM and presents a rendering load.
• Use an aircraft without a visible cockpit object.
  
• Revert to the V6 runway textures. The V7 textures are a lot bigger and may tax old graphics cards. Each of these has the texture files for that kind of surface. The  texture file used for general pavement is named rway_pave.bmp. All the  other files have special markings (lines, numbers, touch-down zone, etc.) Simply copy over the corresponding files from X-Plane V6.70. [Caveat: This advice worked going from 6.70 to early V7 versions. I haven't tried it in a while and it may or may not work with later V7.x versions. Don't even think about it for V8.x.]

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

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

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

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?

Does adding RAM help on other systems?