1 // Copyright 2020 Google LLC.
2 // Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
3 #include "tools/fiddle/examples.h"
4 REG_FIDDLE_ANIMATED(l_system_plant, 256, 256, false, 0, 3) {
5 // L-System
6 // https://en.wikipedia.org/wiki/L-system#Example_7:_Fractal_plant
7
8 struct rules_t {
9 char c;
10 std::string s;
11 };
12
13 rules_t rules[6] = {
14 {'X', "F-[[X]+X]+F[+FX]-X"},
15 {'F', "FF"},
16 {'+', "+"},
17 {'-', "-"},
18 {'[', "["},
19 {']', "]"},
20 };
21
E(std::string s)22 std::string E(std::string s) {
23 if (s.size() == 0) {
24 return "";
25 }
26 for (int i=0; i<6; i++) {
27 if (rules[i].c == s[0]) {
28 return rules[i].s + E(s.substr(1));
29 }
30 }
31 return "";
32 }
33
34 struct Pt {
35 SkScalar x;
36 SkScalar y;
37 SkScalar a;
38 };
39
draw(SkCanvas * canvas)40 void draw(SkCanvas* canvas) {
41 canvas->drawColor(SK_ColorLTGRAY);
42
43 SkPaint p;
44 p.setColor(0xFFA6761D);
45 p.setAntiAlias(true);
46 p.setStyle(SkPaint::kStroke_Style);
47 p.setStrokeWidth(1);
48
49 std::vector<struct Pt> ptstack;
50 std::string plant = E(E(E(E(E("X")))));
51 const double len = 2.5;
52 struct Pt pt = {128, 256, 3.14};
53 SkPath path;
54 path.moveTo(pt.x, pt.y);
55
56 for (std::string::iterator it=plant.begin(); it!=plant.end(); ++it) {
57 if (*it == 'F') {
58 pt.x += len*sin(pt.a);
59 pt.y += len*cos(pt.a);
60 path.lineTo(pt.x, pt.y);
61 } else if (*it == '+') {
62 pt.a += (0.15 + sin(frame*2.0*3.14159)*0.05);
63 } else if (*it == '-') {
64 pt.a += (-0.15 + sin(frame*2.0*3.14159)*0.05);
65 } else if (*it == '[') {
66 ptstack.push_back(pt);
67 } else if (*it == ']') {
68 pt = ptstack.back();
69 ptstack.pop_back();
70 path.moveTo(pt.x, pt.y);
71 }
72 }
73 canvas->drawPath(path, p);
74 }
75 } // END FIDDLE
76