Hallo,
ich möchte mir mit OpenGL etwas visualisieren und habe mir
erstmal ein kleines Testprogramm geschrieben:
fractal.c
#include <GL/glut.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct
{
double a00, a01, a10, a11; /* Transformation matrix */
double b0, b1; /* Constant vector added on */
double statx, staty; /* Coordinates of the stationary point
*/
}
AffineTrans;
/* Number of levels to draw the fractal */
static int num_levels = 0;
/* The definition of the fractal */
static int num_trans;
static AffineTrans *affine;
/* the window title */
#define WIN_TITLE_LENGTH 80
char window_title[ WIN_TITLE_LENGTH + 1 ];
/* The amount the view is translated and scaled */
double xwin = 0.0, ywin = 0.0;
double scale_factor = 1.0;
static void draw_level(
int num,
double m00, double m01, double m10, double m11, double n0, double n1
)
{
/* Draw a fractal transformed by "M", "N" as passed in */
int i;
if( !num )
{
double x0 = m00 * affine[0].statx + m01 * affine[0].staty + n0;
double y0 = m10 * affine[0].statx + m11 * affine[0].staty + n1;
for( i = 1; i < num_trans; i++ )
{
double x1 = m00 * affine[i].statx + m01 * affine[i].staty +
n0;
double y1 = m10 * affine[i].statx + m11 * affine[i].staty +
n1;
glVertex2d ( x0, y0 );
glVertex2d ( x1, y1 );
x0 = x1;
y0 = y1;
}
}
else
/*
* Map each affine transformation in the fractal through
* the one passed in and call draw_level()
*/
for( i = 0; i < num_trans; i++ )
draw_level(
num-1,
m00*affine[i].a00+m01*affine[i].a10,
m00*affine[i].a01+m01*affine[i].a11,
m10*affine[i].a00+m11*affine[i].a10,
m10*affine[i].a01+m11*affine[i].a11,
m00*affine[i].b0 +m01*affine[i].b1 + n0,
m10*affine[i].b0 +m11*affine[i].b1 + n1
);
}
static void Display( void )
{
glClear( GL_COLOR_BUFFER_BIT );
/* the curve */
glPushMatrix();
glScalef(2.5, 2.5, 2.5);
glColor4f(0.0, 0.0, 0.0, 1.0);
glBegin( GL_LINES );
draw_level( num_levels, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0 );
glEnd( );
glPopMatrix();
glutSwapBuffers();
}
static void Reshape( int width, int height )
{
float ar;
glViewport( 0, 0, width, height );
glMatrixMode( GL_PROJECTION );
glLoadIdentity( );
ar = ( float )width / ( float )height;
if( ar > 1 )
glFrustum( -ar, ar, -1.0, 1.0, 2.0, 100.0 );
else
glFrustum( -1.0, 1.0, -1/ar, 1/ar, 2.0, 100.0 );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity( );
xwin = -1.0;
ywin = 0.0;
glTranslated( xwin, ywin, -5.0 );
}
static void Key( unsigned char key, int x, int y )
{
int need_redisplay = 1;
switch (key) {
case 27: /* Escape key */
glutLeaveMainLoop ();
break;
case '+' :
++num_levels;
break;
case '-' :
if ( num_levels > 0 )
--num_levels;
break;
case 'r' : case 'R' :
glMatrixMode ( GL_MODELVIEW );
glLoadIdentity();
xwin = -1.0;
ywin = 0.0;
glTranslated ( xwin, ywin, -5.0 );
break;
default:
need_redisplay = 0;
break;
}
if (need_redisplay)
glutPostRedisplay();
}
static void Special( int key, int x, int y )
{
int need_redisplay = 1;
switch (key) {
case GLUT_KEY_UP :
glMatrixMode ( GL_MODELVIEW );
ywin += 0.1 * scale_factor;
glTranslated ( 0.0, 0.1 * scale_factor, 0.0 );
break;
case GLUT_KEY_DOWN :
glMatrixMode ( GL_MODELVIEW );
ywin -= 0.1 * scale_factor;
glTranslated ( 0.0, -0.1 * scale_factor, 0.0 );
break;
case GLUT_KEY_LEFT :
glMatrixMode ( GL_MODELVIEW );
xwin -= 0.1 * scale_factor;
glTranslated ( -0.1 * scale_factor, 0.0, 0.0 );
break;
case GLUT_KEY_RIGHT :
glMatrixMode ( GL_MODELVIEW );
xwin += 0.1 * scale_factor;
glTranslated ( 0.1 * scale_factor, 0.0, 0.0 );
break;
case GLUT_KEY_PAGE_UP :
glMatrixMode ( GL_MODELVIEW );
glTranslated ( -xwin, -ywin, 0.0 );
glScaled ( 1.25, 1.25, 1.25 );
glTranslated ( xwin, ywin, 0.0 );
scale_factor *= 0.8;
break;
case GLUT_KEY_PAGE_DOWN :
glMatrixMode ( GL_MODELVIEW );
glTranslated ( -xwin, -ywin, 0.0 );
glScaled ( 0.8, 0.8, 0.8 );
glTranslated ( xwin, ywin, 0.0 );
scale_factor *= 1.25;
break;
default:
need_redisplay = 0;
break;
}
if (need_redisplay)
glutPostRedisplay();
}
void readConfigFile ( char *fnme )
{
FILE *fptr = fopen ( fnme, "rt" );
int i;
char inputline [ 256 ];
if ( fptr )
{
/* Read a header line */
fgets( inputline, 256, fptr );
/* Read a comment line */
fgets( inputline, 256, fptr );
/* Read the window title */
fgets( inputline, 256, fptr );
/*
We assume here that this line will not exceed 79 characters
plus a
newline (window_title is 80 characters long). That'll cause a
buffer
overflow. For a simple program like this, though, we're
letting it
slide!
*/
sscanf(
inputline, "%[a-zA-Z0-9!@#$%^&*()+=/\\_-\" ]", window_title
);
/* Read a comment line */
fgets( inputline, 256, fptr );
/* Read the number of affine transformations */
fgets( inputline, 256, fptr );
sscanf( inputline, "%d", &num_trans );
affine = (AffineTrans *)malloc ( num_trans *
sizeof(AffineTrans) );
/* Read a comment line */
fgets( inputline, 256, fptr );
for ( i = 0; i < num_trans; i++ )
{
/* Read an affine transformation definition */
fgets( inputline, 256, fptr );
sscanf(
inputline, "%lf %lf %lf %lf %lf %lf",
&affine[i].a00, &affine[i].a01,
&affine[i].a10, &affine[i].a11,
&affine[i].b0, &affine[i].b1
);
}
}
else /* No data file, set a default */
{
printf( "ERROR opening file <%s>\n", fnme );
strncpy( window_title, "Cantor Dust", WIN_TITLE_LENGTH );
num_trans = 2;
affine = (AffineTrans *)malloc ( num_trans *
sizeof(AffineTrans) );
affine[0].a00 = 0.25; affine[0].a01 = 0.00;
affine[0].a10 = 0.00; affine[0].a11 = 0.25;
affine[0].b0 = 0.0; affine[0].b1 = 0.0;
affine[1].a00 = 0.25; affine[1].a01 = 0.00;
affine[1].a10 = 0.00; affine[1].a11 = 0.25;
affine[1].b0 = 0.5; affine[1].b1 = 0.0;
}
for ( i = 0; i < num_trans; i++ )
{
double m00, m01, m10, m11; /* Matrix "I" minus "A" */
double determ; /* Determinant of this matrix */
/* Calculate the stationary point */
m00 = 1.0 - affine[i].a00;
m01 = - affine[i].a01;
m10 = - affine[i].a10;
m11 = 1.0 - affine[i].a11;
determ = m00 * m11 - m01 * m10;
if ( fabs ( determ ) > 1.e-6 )
{
affine[i].statx = ( m11 * affine[i].b0 - m01 *
affine[i].b1 ) /
determ;
affine[i].staty = ( -m10 * affine[i].b0 + m00 *
affine[i].b1 ) /
determ;
}
else
affine[i].statx = affine[i].staty = 0.0;
}
}
int main(int argc, char *argv[])
{
int fractal_window;
glutInitWindowSize(500, 250);
glutInitWindowPosition ( 140, 140 );
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE );
glutInit(&argc, argv);
if ( argc > 1 )
readConfigFile ( argv[1] );
else
readConfigFile ( "fractals.dat" );
fractal_window = glutCreateWindow( window_title );
glClearColor( 1.0, 1.0, 1.0, 1.0 );
glutReshapeFunc( Reshape );
glutKeyboardFunc( Key );
glutSpecialFunc( Special );
glutDisplayFunc( Display );
glutMainLoop( );
printf( "Back from the 'freeglut' main loop\n" );
return EXIT_SUCCESS;
}
kompiliert mit gcc -o fractal fractal.c -lm -lglut durch, aber
jetzt komm'st:
Auf der Konsole kommt eine Fehlermeldung der Art
[jan@localhost C]$ ./fractal
ERROR opening file <fractals.dat>
freeglut (./fractal): Unable to create direct context rendering for
window 'Cantor Dust'
This may hurt performance.
[jan@localhost C]$
Ok, das mit fractal.dat ist nicht so wichtig, aber die
Performance-geschichte versteh ich nicht.
Danke Jan