Author:

• Name: Carl Banks
  Location: US - United States of America (United States)

To build:

    make all

NOTE: this entry requires the X11/Xlib.h header file and the X11 library to compile. For more information see the FAQ on “X11”.

If you do not have a page up or page down key you might wish to see the Alternate code section below. You may redefine all the keys and the time step with predefined macros, however, so one lacking page up / page down does not strictly need the alternate code; it jut gives those controls a default value. The author provided the following table:

    Control         Description         Default Key
    -------  -------------------------  -----------
     IT         Increase throttle      XK_Page_Up
     DT         Decrease throttle      XK_Page_Down
     FD         Move stick forward     XK_Up
     BK         Move stick back        XK_Down
     LT         Move stick left        XK_Left
     RT         Move stick right       XK_Right
     CS         Center stick           XK_Enter

There is another macro, dt, which is the time step. See some important points on this in the author’s comments in the Alternate Build Instructions section.

If however you wish to change the above controls, see the header file keysym.h for the definitions of other characters that you might wish to use. The name of the macro in the header file is what you need to set the macros to, depending on what controls you wish to redefine. For instance, to set the throttle up and down to u and d:

    make clobber IT=XK_u DT=XK_d all

because in the header file you can see that XK_u corresponds to u and XK_d corresponds to d:

    #define XK_d 0x0064  /* U+0064 LATIN SMALL LETTER D */
    #define XK_u 0x0075  /* U+0075 LATIN SMALL LETTER U */

Note that the keysym.h file is not complete from X11; it’s just the more likely candidates (and some that are probably unlikely :-) ).

The upper case letters would be XK_U and XK_D and you can search the header file for ‘LATIN CAPITAL D’, for example.

For those who do not have a Page Up or Page Down key, see alternate code below. The difference from the alt build and the original entry is that the page up and page down keys are defined to a default but they are hard coded as doing otherwise would necessarily complicate the build instructions. Since you can use the original entry to redefine these this is not a problem and is purely a convenience .. if only for those who are okay with the preselected alternative keys.

To use:

    cat horizon.sc pittsburgh.sc | ./banks

See the author’s remarks in scenery for more details on the scenery files.

Try:

For a fun time after running the above command, hold down the up arrow and left arrow for about 10 seconds and see what happens. Or, if you wish to really use it in a non-silly way, see the author’s remarks for the real controls. Perhaps you can regain control?

Alternate code:

If you do not have access to a page up or page down key, for instance you’re using a Mac, you can use the alternate code (though it actually uses the same code) that will redefine the keys to increase throttle and decrease throttle. This same method can be used with the original code but this sets up predefined keys in place of Page Up and Page Down.

The keys were somewhat arbitrarily selected but it was decided to make them both on the left side of a QWERTY keyboard as one might have a harder time using the arrows at the same time as typing on the right side.

Alternate build:

As the Makefile allows you to configure the keys to use you may redefine the keys but with the alt build you cannot, as described earlier, redefine the page up and page down replacement keys. The other controls you may redefine; this is just a convenience build. If you want to redefine the page up / page down keys you should use the original entry as described in the to build section above.

In the alt build it is f (for page up) and d (for page down) as these are letters on the left side of the keyboard which is easier to use if one is using the right side for movement. These are hard coded, as noted.

To use the default settings for the alternate build:

    make alt

You may change the other keys as described in the build instructions, above, but this alternate code can be seen as an alternative for those who don’t have or don’t want to use page up and page down.

Alternate use:

Use banks.alt as you would banks but use the different keys as configured at compilation.

Judges’ remarks:

What can we say? It’s a flight sim done in 1536 bytes of real code. This one is a real marvel. When people say the size limits are too tight, well, we can just point them at this one. This program really pushes the envelope!

The provided Makefile should work; you will need an X-ish system, and a select(2) system call. More on building in the author remarks.

Carl Banks linked to (on his old website) an interesting article about this entry, a flight simulator in just 1536 bytes, which can be found at https://web.archive.org/web/20040201120708/http://www.idg.co.nz/magazine/pcworld/oct99/code.htm.

Author’s remarks:

You have just stepped out of the real world and into the virtual. You are now sitting in the cockpit of a Piper Cherokee airplane, heading north, flying 1000 feet above ground level.

Use the keyboard to fly the airplane. The arrow keys represent the control stick. Press the Up Arrow key to push the stick forward. Press the left arrow key to move the stick left, and so on. Press Enter to re-center the stick. Use Page Up and Page Down to increase and decrease the throttle, respectively. (The rudder is automatically coordinated with the turn rate, so rudder pedals are not represented.)

On your display, you will see on the bottom left corner three instruments. The first is the airspeed indicator; it tells you how fast you’re going in knots. The second is the heading indicator, or compass. 0 is north, 90 is east, 180 is south, 270 is west. The third instrument is the altimeter, which measures your height above ground level in feet.

Features

• Simulator models a Piper Cherokee, which is a light, single-engine propeller driven airplane.

• The airplane is modeled as a six degree-of-freedom rigid body, accurately reflecting its dynamics (for normal flight conditions, at least).

• Fly through a virtual 3D world, while sitting at your X console.

• Loadable scenery files.

• Head-up display contains three instruments: a true airspeed indicator, a heading indicator (compass), and an altimeter.

• Flight controls may be mapped to any keys at compile time by redefining the macros in the Makefile. Nice if your keyboard doesn’t have arrow keys. (Or if you still use vi. :-)

• Time step size can be set at compile time. This is useful to reduce flicker on network X connections. (But be careful: step sizes longer than about 0.03 seconds tend to have numerical stability problems.)

• Airplane never stalls!

• Airplane never runs out of fuel!

• Fly underground!

• Fly through buildings!

Scenery

Each of the *.sc files is a scenery file. The simulator program reads in the scenery from standard input on startup. You may input more than one scenery file, as long as there are less than 1000 total lines of input.

Here is a brief description of the scenery files:

• horizon.sc

  A horizon, nothing more. You will probably always want to input this piece of scenery.

• mountains.sc

  An alternate horizon; a little more mountainous.

• pittsburgh.sc

  Scenery of downtown Pittsburgh. The downtown area is initially located to your right.

• bb.sc

  Simple obstacle course. Try to fly over the buildings and under the bridges.

• pyramids.sc

  Fly over the tombs of the ancient Pharaohs, in this (fictitious) Egyptian landscape.

• river.sc

  Follow a flowing river from the sky.

A few examples of how to input scenery:

    cat horizon.sc pittsburgh.sc | ./banks
    cat mountains.sc bb.sc | ./banks
    cat mountains.sc river.sc pyramids.sc | ./banks

You can simulate flying through a cloud bank as well:

    ./banks < /dev/null

You will usually want at least a horizon, though.

The format of scenery files is simple, by the way. They’re just a list of 3D coordinates, and the simulator simply draws line segments from point to point as listed in the scenery file. 0 0 0 is used to end a series of consecutive line segments. Note that in the coordinate system used, the third coordinate represents altitude in a negative sense: negative numbers are positive altitudes.

I’m sure you’ll be making your own scenery files very soon!!!

Alternate Build Instructions

Several options must be passed to the compiler to make the build work. The provided Makefile has the appropriate options set to default values. Use this section if you want to compile with different options.

To map a key to a control, you must pass an option to the compiler in the format -Dcontrol=key or if you use the Makefile you can do make control=key.

The possible controls you can map are described in the table below:

    Control         Description         Default Key
    -------  -------------------------  -----------
     IT         Increase throttle      XK_Page_Up
     DT         Decrease throttle      XK_Page_Down
     FD         Move stick forward     XK_Up
     BK         Move stick back        XK_Down
     LT         Move stick left        XK_Left
     RT         Move stick right       XK_Right
     CS         Center stick           XK_Enter

Values for the possible keys can be found in the X Windows header file <X11/keysym.h>. This file is most likely a cross-reference to another header, <X11/keysymdef.h>.

For example, to map Center Stick to the space-bar, the compile option would be -DCS=XK_space or make CS=XK_space.

To set the time step size, you must pass the following option to the compiler: -Ddt=duration, where dt is literal, and where duration is the time in seconds you want the time step to be. Alternatively, if you use the provided Makefile, you may just do make dt=time.

Two things to keep in mind when selecting a time step. Time steps that are too large (more than about 0.03) will cause numerical stability problems and should be avoided. Setting the time step to be smaller than your clock resolution will slow down the simulator, because the system pauses for more time than the simulator expects.

The best advice is to set time step size to your system timer resolution. Try a longer period if you’re getting too much flicker.

Primary files

• banks.c - entry source code
• Makefile - entry Makefile
• banks.orig.c - original source code
• keysym.h - header file to help identify some key symbols
• bb.sc - scenery file
• horizon.sc - scenery file
• mountains.sc - scenery file
• pittsburgh.sc - scenery file
• pyramids.sc - scenery file
• river.sc - scenery file

Secondary files

• 1998_banks.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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