Simple GLUT library issue - c++

Question

This will be my first post on stackoverflow.
So, I'm making a simple program(VISUAL STUDIO 2012), using GLUT library. I basically try to display a torus, but instead I get a black screen.
#include<gl/glut.h>
#include<math.h>
GLfloat r=8;
GLint spin=0;
GLfloat light_position[]={0.0,0.0,0.0,1.0};
GLfloat ex,ey=0, ez, upx=0, upy=0, upz=0;
void init(){
glClearColor(1.0,1.0,1.0,1.0);
glShadeModel(GL_FLAT);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_DEPTH_TEST);
}
void display(void){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_TEST);
glPushMatrix();
double sine = (float)sin((float)spin);
double cosine = (float)cos((float)spin);
ex=r*sine;
ez=r*cosine;
gluLookAt(ex,ey,-5.0,0,0,0,upx,upy,upz);
glColor3b(1.0,0,0);
glutSolidTorus(0.275,0.85,8,15);
glPopMatrix();
glFlush();
}
void reshape(int w, int h)
{
glViewport(0,0,(GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
gluPerspective(40.0, (GLfloat) w/(GLfloat) h, 1.0,20.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glLightfv( GL_LIGHT0, GL_POSITION, light_position);
}
void mouse(int button, int state, int x, int y)
{
switch(button)
{
case GLUT_LEFT_BUTTON:
if( state == GLUT_DOWN){
spin = (spin+15)%360;
glutPostRedisplay();
}
break;
default:
break;
}
}
void main(int argc, char **argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_RGBA);
glutInitWindowSize(800,600);
glutInitWindowPosition(300,300);
glutCreateWindow("Light Rotating Torus");
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutMouseFunc(mouse);
glutMainLoop();
}
Can somebody modify it/give a hint, so it displays something?
Thanks

Answer 1

The most obvious problem is your UP vector. You set upx, upy and upz. That is not a valid up vector, try changing upy to 1.0f. Because of this, your torus was probably rendered out of screen.
Also, glClear doesn't take GL_DEPTH_TEST as a parameter.
Correct call should be:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
Because of this, your screen was not cleared and stayed black (while you set glClearColor to be white).
And lastly, main function should always return int, never void (though it doesn't change anything in your case)