1 /* fractals_random.c */
2 /* This demo shows a single-buffering "freeglut" example. */
5 * Program to draw a fractal by Michael Barnsley's stochastic algorithm.
7 * (1) Define the affine transformations (of the form r(i+1) = A r(i) + b )
8 * (2) Find the stationary point for the first transformation
10 * - Pick a random integer between 1 and the number of transformations (inclusive)
11 * - Send the current point through the transformation to create the new current point
12 * - Plot the new current point
17 * PgUp, PgDn - increase/decrease scaling
18 * Arrow keys - translate viewing section
23 #include <GL/freeglut.h>
30 double a00, a01, a10, a11 ; /* Transformation matrix */
31 double b0, b1 ; /* Constant vector added on */
32 double statx, staty ; /* Coordinates of the stationary point */
36 /* Number of levels to draw the fractal */
37 static int num_levels = 0 ;
39 /* The definition of the fractal */
40 static int num_trans ;
41 static AffineTrans *affine ;
43 /* the window title */
44 char window_title [ 80 ] ;
46 /* The amount the view is translated */
47 float xwin = 0.0, ywin = 0.0 ;
48 float scale_factor = 1.0 ;
50 /* The current point */
51 float current_x = 0.0, current_y = 0.0 ;
53 static void draw_level ( int num, double m00, double m01, double m10, double m11, double n0, double n1 )
55 /* Draw a fractal transformed by "M", "N" as passed in */
58 for ( i = 0; i < 10; i++ )
60 int random = rand () * num_trans / RAND_MAX ;
61 float new_x = affine[random].a00 * current_x + affine[random].a01 * current_y + affine[random].b0 ;
62 float new_y = affine[random].a10 * current_x + affine[random].a11 * current_y + affine[random].b1 ;
64 glVertex2f ( new_x, new_y ) ;
75 glScalef(2.5, 2.5, 2.5);
77 glColor4f(0.0, 0.0, 0.0, 1.0);
78 glBegin ( GL_POINTS ) ;
79 draw_level ( num_levels, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0 );
83 glutPostRedisplay(); /* Needed so that this function will be called again */
87 Reshape(int width, int height)
90 glViewport(0, 0, width, height);
91 glMatrixMode(GL_PROJECTION);
93 ar = (float) width / (float) height;
94 glFrustum(-ar, ar, -1.0, 1.0, 2.0, 100.0);
95 glMatrixMode(GL_MODELVIEW);
99 glTranslatef(xwin, ywin, -5.0);
103 Key(unsigned char key, int x, int y)
106 case 27: /* Escape key */
107 glutLeaveMainLoop ();
110 case 'r' : case 'R' :
111 glMatrixMode(GL_MODELVIEW);
115 glTranslatef(xwin, ywin, -5.0);
120 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
126 Special(int key, int x, int y)
130 glMatrixMode(GL_MODELVIEW);
131 ywin += 0.1 * scale_factor ;
132 glTranslatef(0.0, 0.1 * scale_factor, 0.0);
136 glMatrixMode(GL_MODELVIEW);
137 ywin -= 0.1 * scale_factor ;
138 glTranslatef(0.0, -0.1 * scale_factor, 0.0);
142 glMatrixMode(GL_MODELVIEW);
143 xwin -= 0.1 * scale_factor ;
144 glTranslatef(-0.1 * scale_factor, 0.0, 0.0);
147 case GLUT_KEY_RIGHT :
148 glMatrixMode(GL_MODELVIEW);
149 xwin += 0.1 * scale_factor ;
150 glTranslatef(0.1 * scale_factor, 0.0, 0.0);
153 case GLUT_KEY_PAGE_UP :
154 glMatrixMode(GL_MODELVIEW);
155 glTranslatef ( -xwin, -ywin, 0.0 ) ;
156 glScalef(1.25, 1.25, 1.25);
157 glTranslatef ( xwin, ywin, 0.0 ) ;
158 scale_factor *= 0.8 ;
161 case GLUT_KEY_PAGE_DOWN :
162 glMatrixMode(GL_MODELVIEW);
163 glTranslatef ( -xwin, -ywin, 0.0 ) ;
164 glScalef(0.8, 0.8, 0.8);
165 glTranslatef ( xwin, ywin, 0.0 ) ;
166 scale_factor *= 1.25 ;
170 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
175 void readConfigFile ( char *fnme )
177 FILE *fptr = fopen ( fnme, "rt" ) ;
179 char inputline [ 256 ] ;
181 /* Read a header line */
182 fgets ( inputline, 256, fptr ) ;
184 /* Read a comment line */
185 fgets ( inputline, 256, fptr ) ;
187 /* Read the window title */
188 fgets ( inputline, 256, fptr ) ;
189 sscanf ( inputline, "%s", window_title ) ;
191 /* Read a comment line */
192 fgets ( inputline, 256, fptr ) ;
194 /* Read the number of affine transformations */
195 fgets ( inputline, 256, fptr ) ;
196 sscanf ( inputline, "%d", &num_trans ) ;
198 affine = (AffineTrans *)malloc ( num_trans * sizeof(AffineTrans) ) ;
200 /* Read a comment line */
201 fgets ( inputline, 256, fptr ) ;
203 for ( i = 0; i < num_trans; i++ )
205 double m00, m01, m10, m11 ; /* Matrix "I" minus "A" */
206 double determ ; /* Determinant of this matrix */
208 /* Read an affine transformation definition */
209 fgets ( inputline, 256, fptr ) ;
210 sscanf ( inputline, "%lf %lf %lf %lf %lf %lf", &affine[i].a00, &affine[i].a01,
211 &affine[i].a10, &affine[i].a11, &affine[i].b0, &affine[i].b1 ) ;
213 /* Calculate the stationary point */
215 m00 = 1.0 - affine[i].a00 ;
216 m01 = - affine[i].a01 ;
217 m10 = - affine[i].a10 ;
218 m11 = 1.0 - affine[i].a11 ;
220 determ = m00 * m11 - m01 * m10 ;
222 if ( fabs ( determ ) > 1.e-6 )
224 affine[i].statx = ( m11 * affine[i].b0 - m01 * affine[i].b1 ) / determ ;
225 affine[i].staty = ( -m10 * affine[i].b0 + m00 * affine[i].b1 ) / determ ;
228 affine[i].statx = affine[i].staty = 0.0 ;
233 main(int argc, char *argv[])
238 readConfigFile ( argv[1] ) ;
240 readConfigFile ( "fractals.dat" ) ;
242 glutInit(&argc, argv);
243 glutInitWindowSize(500, 250);
244 glutInitWindowPosition ( 140, 140 ) ;
246 glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH);
248 fractal_window = glutCreateWindow( window_title );
250 glClearColor(1.0, 1.0, 1.0, 1.0);
252 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
254 glutReshapeFunc(Reshape);
255 glutKeyboardFunc(Key);
256 glutSpecialFunc(Special);
257 glutDisplayFunc(Display);
261 printf ( "Back from the 'freeglut' main loop\n" ) ;
263 return 0; /* ANSI C requires main to return int. */