1. #include <GL/gl.h>
2. #include <GL/glut.h>
3. #include <cstdlib>
4. #include <ctime>
5.  
6. float randomFloat()
7. {
8.     return static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
9. }
10.  
11. void drawSquare(const float x, const float y, const float size)
12. {
13.     glBegin(GL_POLYGON);
14.     glColor3f(randomFloat(), randomFloat(), randomFloat());
15.     glVertex2f(x, y);
16.     glColor3f(randomFloat(), randomFloat(), randomFloat());
17.     glVertex2f(x + size, y);
18.     glColor3f(randomFloat(), randomFloat(), randomFloat());
19.     glVertex2f(x + size, y - size);
20.     glColor3f(randomFloat(), randomFloat(), randomFloat());
21.     glVertex2f(x, y - size);
22.     glEnd();
23. }
24.  
25. void drawFractal(const int levelsCount, const float randomness, const float x, const float y, const float rectSize)
26. {
27.     float singleRectSize = rectSize / 3;
28.  
29.     for (int i = 0; i < 3; i++)
30.     {
31.         for (int j = 0; j < 3; j++)
32.         {
33.             if (i == 1 && j == 1)
34.                 continue;
35.  
36.             if (levelsCount == 0)
37.                 drawSquare(x + i * singleRectSize  + singleRectSize * randomFloat() * randomness, y - j * singleRectSize + singleRectSize * randomFloat() * randomness, singleRectSize);
38.             else
39.                 drawFractal(levelsCount - 1, randomness, x + i * singleRectSize + singleRectSize * randomFloat() * randomness, y - j * singleRectSize + singleRectSize * randomFloat() * randomness, singleRectSize);
40.         }
41.     }
42. }
43.  
44. void renderScene()
45. {
46.     glClear(GL_COLOR_BUFFER_BIT);
47.  
48.     glColor3f(0.0F, 1.0F, 0.0F);
49.  
50.     int levelCount = 2;
51.     float startX = -75.0F;
52.     float startY = 75.0F;
53.     float fractalSize = 150.0F;
54.     float randomness = 0.05;
55.  
56.     drawFractal(levelCount, randomness, startX, startY, fractalSize);
57.  
58.     glFlush();
59. }
60.  
61. void changeSize(int width, int height)
62. {
63.     if (height == 0)
64.         height = 1;
65.  
66.     glViewport(0, 0, width, height);
67.  
68.     glMatrixMode(GL_PROJECTION);
69.     glLoadIdentity();
70.  
71.     float aspectRatio = static_cast<float>(width) / static_cast<float>(height);
72.  
73.     if (width <= height)
74.         glOrtho(-100.0, 100.0, -100.0 / aspectRatio, 100.0 / aspectRatio, 1.0, -1.0);
75.     else
76.         glOrtho(-100.0 * aspectRatio, 100.0 * aspectRatio, -100.0, 100.0, 1.0, -1.0);
77.  
78.     glMatrixMode(GL_MODELVIEW);
79.     glLoadIdentity();
80. }
81.  
82. void myInit()
83. {
84.     std::srand(std::time(nullptr));
85.     glClearColor(0.5F, 0.5F, 0.5F, 1.0F);
86. }
87.  
88. int main(int argc, char *argv[])
89. {
90.     glutInit(&argc, argv);
91.     glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);
92.     glutCreateWindow("Dywan Sierpinskiego");
93.  
94.     glutDisplayFunc(renderScene);
95.     glutReshapeFunc(changeSize);
96.     myInit();
97.  
98.     glutMainLoop();
99.  
100.     return 0;
101. }