76 lines
1.7 KiB
C++
76 lines
1.7 KiB
C++
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// Copyright 2020 Google LLC.
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// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
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#include "tools/fiddle/examples.h"
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REG_FIDDLE_ANIMATED(l_system_plant, 256, 256, false, 0, 3) {
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// L-System
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// https://en.wikipedia.org/wiki/L-system#Example_7:_Fractal_plant
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struct rules_t {
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char c;
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std::string s;
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};
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rules_t rules[6] = {
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{'X', "F-[[X]+X]+F[+FX]-X"},
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{'F', "FF"},
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{'+', "+"},
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{'-', "-"},
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{'[', "["},
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{']', "]"},
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};
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std::string E(std::string s) {
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if (s.size() == 0) {
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return "";
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}
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for (int i=0; i<6; i++) {
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if (rules[i].c == s[0]) {
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return rules[i].s + E(s.substr(1));
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}
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}
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return "";
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}
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struct Pt {
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SkScalar x;
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SkScalar y;
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SkScalar a;
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};
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void draw(SkCanvas* canvas) {
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canvas->drawColor(SK_ColorLTGRAY);
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SkPaint p;
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p.setColor(0xFFA6761D);
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p.setAntiAlias(true);
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p.setStyle(SkPaint::kStroke_Style);
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p.setStrokeWidth(1);
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std::vector<struct Pt> ptstack;
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std::string plant = E(E(E(E(E("X")))));
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const double len = 2.5;
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struct Pt pt = {128, 256, 3.14};
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SkPath path;
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path.moveTo(pt.x, pt.y);
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for (std::string::iterator it=plant.begin(); it!=plant.end(); ++it) {
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if (*it == 'F') {
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pt.x += len*sin(pt.a);
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pt.y += len*cos(pt.a);
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path.lineTo(pt.x, pt.y);
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} else if (*it == '+') {
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pt.a += (0.15 + sin(frame*2.0*3.14159)*0.05);
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} else if (*it == '-') {
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pt.a += (-0.15 + sin(frame*2.0*3.14159)*0.05);
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} else if (*it == '[') {
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ptstack.push_back(pt);
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} else if (*it == ']') {
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pt = ptstack.back();
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ptstack.pop_back();
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path.moveTo(pt.x, pt.y);
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}
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}
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canvas->drawPath(path, p);
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}
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} // END FIDDLE
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