why won't this super-simple glut program run right?

[jmg]

The following code builds with no warnings, but when run displays nothing.

I'm on Redhat9, glxinfo tells me direct rendering is working fine, glxgears runs wildly fast, it's a 106 miles to Chicago, we've got a full tank of gas, half-a-pack of cigarettes,.. oh wait.



// tester.cpp

#include <GL/glut.h>

//================================================
void my_init();
void my_display_func();
void my_reshape_func( int w, int h );

//================================================
int main( int argc, char * argv[] )
{
glutInit( &amp;argc, argv );
glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
glutInitWindowSize( 600, 600 );
glutInitWindowPosition( 50, 50 );
glutCreateWindow( "tester" );

my_init();

glutDisplayFunc( my_display_func );
glutReshapeFunc( my_reshape_func );

glutMainLoop();
return 0;
}

//================================================
void my_init()
{
glClearColor( 0.0, 0.0, 0.0, 0.0 );
glEnable( GL_DEPTH_TEST );
}

//================================================
void my_display_func()
{
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

glColor3f( 0.1, 0.7, 0.3 );
glBegin( GL_LINE_STRIP );
glVertex3d( 0.2, 0.2, 0.0 );
glVertex3d( -0.2, 0.2, 0.0 );
glVertex3d( -0.2, -0.2, 0.0 );
glVertex3d( 0.2, -0.2, 0.0 );
glEnd();

glutSwapBuffers();
}

//================================================
void my_reshape_func( int w, int h )
{
if ( w > h )
{
glViewport( w/2 - h/2, // x_bottom_left_corner
0, // y_bottom_left_corner
h, // width (x, to the left)
h ); // height (y, up)
}
else
{
glViewport( 0, h/2 - w/2, w, w );
}

glMatrixMode( GL_PROJECTION );
glLoadIdentity();
gluPerspective( 35.0, // fovy
1.0, // aspect
2.0, // near
6.0 ); // far

glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
gluLookAt( 0.0, 0.0, 4.0, // eye position
0.0, 0.0, 0.0, // looking at
0.0, 1.0, 0.0 ); // which way is up

glutPostRedisplay();
}


and makefile is



# makefile for glut_tester
#

APP_NAME = glut_tester
LIBS = -lglut -lGLU -lGL -L/usr/X11R6/lib -lXmu -lXi

$(APP_NAME): main.o
g++ main.o -Wall -ansi -pedantic-errors -o $(APP_NAME) $(LIBS)

main.o: main.cpp
g++ -c main.cpp

clean:
rm -f $(APP_NAME)
rm -f *.o

[shinpaughp]

Ignore thi
Its probably because your z coords are set to 0.0. They are being culled by the frustum. Try putting them at -3.0 in your glVertex calls.

Edit:
Ooops. Just saw your gluLookAt. I'll test it for you. No problems. I see 3 green lines as would be expected. Unfortunately that is on Windows using VC++7.

Put the following just after glClearColor in your myinit func.




GLenum err = glGetError();
if (err)
{
const GLubyte* errstr = gluErrorString(err);
printf((char*)errstr);
}


If you get an error then it is likely that a valid context could not be created by GLUT, so you may need to update your video drivers or OpenGL is not supported by your video card or I have no clue and hopefully someone else with more Linux experience than myself will come along.

If you do not get an error, then I still don't know because I copied your code exactly and only added #pragma comments to link libraries and it worked.

[This message has been edited by shinpaughp (edited 04-08-2003).]

[nexusone]

I have redhat 8 at home, later can see what is going on.

I just posted some of my linux GLUT code on my website, would like some feed back from other linux users.
www.angelfire.com/linux/nexusone/ (http://www.angelfire.com/linux/nexusone/)

[jmg]

Thanks shinpaughp. I'm at work, but I tried this code here on Solaris 8 sparc and it works fine.

nexusone, is your glut stuff working fine on RH8?

Looks like this is linux-specific, so I'll ask about it in the linux forum. Thanks again.

[nexusone]

Yes, only had to add a header that was not needed with DEV-C++, I think it was something like stdlib.h and string.h.

I have three programs running under glut in RH 8.0 linux, with two of them posted on my website.
I had done some simple stuff under 7.2, but did not use glut, just used KDE framework code to open a window.

Also I downloaded the glut rpm's from redhat, both the runtime and dev lib's.



Originally posted by jmg:
Thanks shinpaughp. I'm at work, but I tried this code here on Solaris 8 sparc and it works fine.

nexusone, is your glut stuff working fine on RH8?

Looks like this is linux-specific, so I'll ask about it in the linux forum. Thanks again.

[cbwan]

try to add glDisable(GL_CULL_FACE) in your gl inits

cb