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86 lines
2.5 KiB
Markdown
86 lines
2.5 KiB
Markdown
# lsystem2
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`lsystem2` is a 2D implementation of [L-system](https://en.wikipedia.org/wiki/L-system). It's based on the algorithm of turtle grahpics. Instructions for generation of rules are as follows:
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F Move forward and draw line
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f Move forward without drawing a line
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+ Turn left
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- Turn right
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| Reverse direction (ie: turn by 180 degrees)
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[ Push current turtle state onto stack
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] Pop current turtle state from the stack
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**Since:** 2.4
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## Parameters
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- `axiom` : The initial state of the system.
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- `rules` : A list of production rules. The first element of each rule is the predecessor, and the second is the successor.
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- `n` : Iteration times.
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- `angle` : Used when turing.
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- `leng` : Used when forwarding. Default to `1`.
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- `heading` : The initial angle of the turtle. Default to `0`.
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- `start` : The starting point of the turtle. Default to `[0, 0]`.
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- `forward_chars` : Chars used for forwarding after the last iteration. Default to `'F'`.
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- `rule_prs` : The probabilities for taking rules. If each rule is chosen with a certain probability, it's a stochastic L-system. Each probability value for a rule ranges from 0 to 1.
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- `seed` : Optional. Seed value for random number generator for repeatable results. **Since:** 3.3.
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## Examples
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[lsystem2-collections.scad](https://github.com/JustinSDK/dotSCAD/blob/master/examples/turtle/lsystem2_collection.scad) collects several L-system grammars. Here's one of them.
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use <turtle/lsystem2.scad>
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use <line2d.scad>
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for(line = fern()) {
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line2d(
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line[0],
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line[1],
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.2,
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p1Style = "CAP_ROUND",
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p2Style = "CAP_ROUND"
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);
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}
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function fern(n = 8, angle = 4, leng = 1, heading = 0, start = [0, 0]) =
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let(
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axiom = "EEEA",
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rules = [
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["A", "[++++++++++++++EC]B+B[--------------ED]B+BA"],
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["C", "[---------EE][+++++++++EE]B+C"],
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["D", "[---------EE][+++++++++EE]B-D"]
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]
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)
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lsystem2(axiom, rules, n, angle, leng, heading, start, forward_chars = "ABCDE");
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// a stochastic L-system
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use <turtle/lsystem2.scad>
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use <line2d.scad>
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for(line = weed()) {
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line2d(
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line[0],
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line[1],
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.2,
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p1Style = "CAP_ROUND",
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p2Style = "CAP_ROUND"
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);
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}
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function weed(n = 6, angle = 22.5, leng = 1, heading = 0, start = [0, 0]) =
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let(
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axiom = "F",
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rules = [
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["F", "FF-[XY]+[XY]"],
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["X", "+FY"],
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["Y", "-FX"]
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]
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)
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lsystem2(axiom, rules, n, angle, leng, heading, start, rule_prs = [0.8, 0.8, 0.8]);
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