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() >> 10) % num_trans;
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 );
84 // glutSwapBuffers(); /* Should NOT be here... This is a Single-Buffered Program! */
85 glutPostRedisplay(); /* Needed so that this function will be called again */
89 Reshape(int width, int height)
92 glViewport(0, 0, width, height);
93 glMatrixMode(GL_PROJECTION);
95 ar = (float) width / (float) height;
96 glFrustum(-ar, ar, -1.0, 1.0, 2.0, 100.0);
97 glMatrixMode(GL_MODELVIEW);
101 glTranslatef(xwin, ywin, -5.0);
105 Key(unsigned char key, int x, int y)
108 case 27: /* Escape key */
109 glutLeaveMainLoop ();
112 case 'r' : case 'R' :
113 glMatrixMode(GL_MODELVIEW);
117 glTranslatef(xwin, ywin, -5.0);
122 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
128 Special(int key, int x, int y)
132 glMatrixMode(GL_MODELVIEW);
133 ywin += 0.1 * scale_factor ;
134 glTranslatef(0.0, 0.1 * scale_factor, 0.0);
138 glMatrixMode(GL_MODELVIEW);
139 ywin -= 0.1 * scale_factor ;
140 glTranslatef(0.0, -0.1 * scale_factor, 0.0);
144 glMatrixMode(GL_MODELVIEW);
145 xwin -= 0.1 * scale_factor ;
146 glTranslatef(-0.1 * scale_factor, 0.0, 0.0);
149 case GLUT_KEY_RIGHT :
150 glMatrixMode(GL_MODELVIEW);
151 xwin += 0.1 * scale_factor ;
152 glTranslatef(0.1 * scale_factor, 0.0, 0.0);
155 case GLUT_KEY_PAGE_UP :
156 glMatrixMode(GL_MODELVIEW);
157 glTranslatef ( -xwin, -ywin, 0.0 ) ;
158 glScalef(1.25, 1.25, 1.25);
159 glTranslatef ( xwin, ywin, 0.0 ) ;
160 scale_factor *= 0.8 ;
163 case GLUT_KEY_PAGE_DOWN :
164 glMatrixMode(GL_MODELVIEW);
165 glTranslatef ( -xwin, -ywin, 0.0 ) ;
166 glScalef(0.8, 0.8, 0.8);
167 glTranslatef ( xwin, ywin, 0.0 ) ;
168 scale_factor *= 1.25 ;
172 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
177 void readConfigFile ( char *fnme )
179 FILE *fptr = fopen ( fnme, "rt" ) ;
181 char inputline [ 256 ] ;
183 /* Read a header line */
184 fgets ( inputline, 256, fptr ) ;
186 /* Read a comment line */
187 fgets ( inputline, 256, fptr ) ;
189 /* Read the window title */
190 fgets ( inputline, 256, fptr ) ;
191 /* We assume here that this line will not exceed 79 characters plus a
192 newline (window_title is 80 characters long). That'll cause a buffer
193 overflow. For a simple program like this, though, we're letting it
196 sscanf ( inputline, "%[a-zA-Z0-9!@#$%^&*()+=/\\_-\" ]", window_title ) ;
198 /* Read a comment line */
199 fgets ( inputline, 256, fptr ) ;
201 /* Read the number of affine transformations */
202 fgets ( inputline, 256, fptr ) ;
203 sscanf ( inputline, "%d", &num_trans ) ;
205 affine = (AffineTrans *)malloc ( num_trans * sizeof(AffineTrans) ) ;
207 /* Read a comment line */
208 fgets ( inputline, 256, fptr ) ;
210 for ( i = 0; i < num_trans; i++ )
212 double m00, m01, m10, m11 ; /* Matrix "I" minus "A" */
213 double determ ; /* Determinant of this matrix */
215 /* Read an affine transformation definition */
216 fgets ( inputline, 256, fptr ) ;
217 sscanf ( inputline, "%lf %lf %lf %lf %lf %lf", &affine[i].a00, &affine[i].a01,
218 &affine[i].a10, &affine[i].a11, &affine[i].b0, &affine[i].b1 ) ;
220 /* Calculate the stationary point */
222 m00 = 1.0 - affine[i].a00 ;
223 m01 = - affine[i].a01 ;
224 m10 = - affine[i].a10 ;
225 m11 = 1.0 - affine[i].a11 ;
227 determ = m00 * m11 - m01 * m10 ;
229 if ( fabs ( determ ) > 1.e-6 )
231 affine[i].statx = ( m11 * affine[i].b0 - m01 * affine[i].b1 ) / determ ;
232 affine[i].staty = ( -m10 * affine[i].b0 + m00 * affine[i].b1 ) / determ ;
235 affine[i].statx = affine[i].staty = 0.0 ;
240 main(int argc, char *argv[])
245 readConfigFile ( argv[1] ) ;
247 readConfigFile ( "fractals.dat" ) ;
249 glutInit(&argc, argv);
250 glutInitWindowSize(500, 250);
251 glutInitWindowPosition ( 140, 140 ) ;
253 glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH);
255 fractal_window = glutCreateWindow( window_title );
257 glClearColor(1.0, 1.0, 1.0, 1.0);
259 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
261 glutReshapeFunc(Reshape);
262 glutKeyboardFunc(Key);
263 glutSpecialFunc(Special);
264 glutDisplayFunc(Display);
268 printf ( "Back from the 'freeglut' main loop\n" ) ;
270 return 0; /* ANSI C requires main to return int. */