README.md

fblife

Version 1.0a

What is this?

Yet another implementation of Conway's 'Game of Life' cellular simulation, for use with the Linux framebuffer. This program draws directly on the framebuffer, and is optimized for embedded Linux systems like the Raspberry Pi. It doesn't require X or any desktop environment. It has a large number of configuration settings that can be used to tune the simulation.

Building

The usual:

$ make
$ sudo make install 

Command-line options

--b-rule=digits

Cell birth rule. See note 'Rules' below.

-b,--border-color=color

Sets the cell border to the specific colour. Colour can be one of the basic HTML colour name: black, white, red, lime, blue, yellow, cyan, magenta, silver, maroon, olive, green, purple, teal, navy; or it can be a hexadecimal string of the form "#RRGGBB".

-c,--color=color

Cell body colour. See --border-colour for more details.

-e,--erase

Erase framebuffer (to black) before starting.

-f,--fbdev=device

Framebuffer device. Defaults to /dev/fb0.

-h,--height=N

Sets the height in cells (not pixels) of the display. The pixel size will be the height multiplied by the cell size. Defaults to 20 cells.

--log-level=N`

Sets the logging verbosity from 0-5. Levels higher than 3 will probably only be comprehensible if read alongside the source code.

-i,--interval=N

Time to wait between update cycles, in milliseconds Setting this to zero can produce some very interesting displays on fast harder, but will seriously tax the CPU. Default value is 1000 msec.

-m,--max-cycles=N

Maximum number of simulation cycles, before reseeding the cells. Although the program will automatically reseed when the pattern is static, it's possible to get into a repeated loop of two or three patterns, which isn't very interesting. The program can't detect this kind of thing automatically, so it's useful to set a limit on the number of simulation cycles. The faster the simulation is running (small values of --interval) the larger --max-cycles will need to be. The default is 60, which gives a one-minute run with the default interval of one second.

-p,--percent=N

Percentage coverage with live cells when seeding the simulation. The default is 30%; values less than 20% and greater the 70% tend to result in very short-lived runs, at least with the default rules.

--s-rule=digits

Cell survivorship rule. See note 'Rules' below.

-w,--width=N

Sets the width in cells (not pixels) of the display. The pixel size will be the width multiplied by the cell size. Defaults to 20 cells.

-s,--cell-size=pixels

Size of a cell in pixels. Default is 20 pixels.

-x,--x=X

X position of the top-left corner of the display area, in pixels. The default is to centre on the screen.

-y,--y=Y

R position of the top-left corner of the display area, in pixels. The default is to centre on the screen.

User and system RC files

All the command-line options can also be set in one or other of the RC files: /etc/fblife.rc and $HOME/.fblife.rc. The format is key-value, one entry on each line. Both The keys correspond to the long form of the command line option.

Rules

The rule for cell lifetime in the original Game of Life can be expressed as "B3/S23". That is, a cell is born into an empty space if the space has (exactly) three live neighbours, and survives if it has 2 or 3 neighbours. Otherwise, it dies.

There are many similar rules that can be used, although the vast majority are uninteresting -- either the grid is filled, or completely emptied, in a few cycles.

fblife allows the birth rule and survivorship rule to be set, using the --b-rule and --s-rule options. Each option takes a string of digits, representing the number of neighbouring cells. So, for example, --b-rule 36 means that a cell well be born into an space with 3 or 6 neighbours. This rule, combined with --s-rule 23 produces the B36/S23 "HighLife" behaviour, which can create interesting behaviour, particularly with smaller initial coverage.

Notes

This program probably won't work under X, because the X server will either disable the framebuffer, or compete for its attention. For testing purposes, it should work on a desktop system is you switch to a terminal console (e..g, ctrl+alt+F2).

To run fblife you'll need read/write access to the framebuffer. You can do this by running as root or as a user which is in the same group as the /dev/fbX framebuffer device.

fblife sends the control sequence to disable the flashing cursor to the current terminal, and re-enables it on exit. This is only a helpful thing to do if you're running the utility from an actual console, of course. If you're not, presumably you will have other mechanisms to manage the cursor.

Fun fact: fblife has nearly 7 000 lines of C, or which only about 200 are for the actual simulation. Most of the rest are for processing the command line and drawing on the framebuffer.

Legal, etc

fblife is copyright (c)2020 Kevin Boone, and distributed under the terms of the GNU Public Licence, version 3.0. Essentially that means you may use the software however you wish, so long as the source code continues to be made available, and the original author is acknowledged. There is no warranty of any kind.