I will write a README when the project is done.
The system reads its configuration from the "config.txt" file. The file
must contain only ASCII characters. It starts with the L-system definition
(replacement rules). Following a line containing the keyword actions, the
file switches to defining the drawing actions the "turtle" takes when
encountering each character. (The actions line must occur exactly once in the
config.)
If you want a longer example, the default "config.txt" contains instructions for drawing the dragon curve, and is shown below:
init F
F F+G
G F-G
actions
F
move_forward 1.0
G
move_forward 1.0
-
rotate -90.0
+
rotate 90.0
Any lines starting with # in the config file are ignored. So, in addition to
L-system characters being limited to ASCII, non-printing, whitespace
characters, and the # character are not allowed in replacement rules. Note
that the # must be the first non-whitespace character in the line.
The first part of the config defines the replacement rules. This section of
the file ends when the line containing the word actions is encountered.
Exactly one line in this part of the file must give the initial contents of the
L-system string:
init <initial text>
All other non-blank and non-comment lines in this section take the following format:
<character> <string of replacement characters>
The character is separated from the string of replacements by one or more tab or space characters.
Characters with no defined replacement rules are left as-is during L-system iteration. Any line containing a character with no following replacement text indicates that the character is to be deleted when encountered (i.e. replaced with a blank string).
Each character can have at most one replacement rule.
Following the actions line, the config switches to defining what each
character means for drawing the graphics. Actions for a character are defined
as follows:
<character>
<action 1>
<action 2>
...
<action n>
In other words, the character must first appear on a line by itself. The following lines must contain the arbitrary number of actions to be taken when the character is processed. The list of actions ends when either the end of the file is reached or another line containing a single character is reached. (Note that none of the actions are a single character long, so there is no ambiguity between lines containing a single character and lines containing an action.)
Each character is allowed at most one associated sequence of actions. Any character that does not appear in the actions section prompts no drawing actions when rendering the L-system. (This can also be achieved by including a character in the actions section, but not specifying any actions after it.)
The following list of actions are supported:
-
move_forward <distance>: Moves the turtle forward, drawing a line, the given distance. The distance is a floating-point number of units. Units are not particularly relevant, because the resulting 3D rendering will be scaled to fit in the viewport regardless. -
rotate <degrees>: Rotates the turtle to its left by the given floating-point number of degrees. -
yaw <degrees>: The same as therotateaction. -
pitch <degrees>: Rotates the turtle in the upwards direction by the given floating-point number of degrees. -
roll <degrees>: Rotates the turtle by the given number of degrees about its forward-facing axis. -
move_forward_nodraw <distance>: Likemove_forward, but does not draw a line segment.
Prior to taking any actions, the turtle is initialized at position (0, 0, 0), facing in the positive-X direction, with its pitch and roll set so that its "back" is facing upwards; in the positive-Y direction.