Rotate a simple polygon in OpenGL - opengl

Question

I follow the code tutorial from the OpenGL programming book, but it doesn't work. It is showing white rectangle at the top left of my window. Could you please tell me what could be wrong with it?
#include<windows.h>
#include <GL/glut.h>
float yRot=0.0;
void Render()
{
//clear color and depth buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();//load identity matrix
glTranslatef(0.0f,0.0f,-4.0f);//move forward 4 units
//rotate along the y-axis
glRotatef(yRot,0.0f,1.0f,0.0f);
glColor3f(0.0f,0.0f,1.0f); //blue color
glBegin(GL_POLYGON);//begin drawing of polygon
glVertex3f(-0.5f,0.5f,0.0f);//first vertex
glVertex3f(0.5f,0.5f,0.0f);//second vertex
glVertex3f(1.0f,0.0f,0.0f);//third vertex
glVertex3f(0.5f,-0.5f,0.0f);//fourth vertex
glVertex3f(-0.5f,-0.5f,0.0f);//fifth vertex
glVertex3f(-1.0f,0.0f,0.0f);//sixth vertex
glEnd();//end drawing of polygon
yRot+=0.1f;//increment the yRot variable
}
//method the reshape the entire figure.
void reshape(int x, int h){
glViewport(0,0,x,h);
}
void init()
{
glClearColor(0.0,0.0,0.2,0.8);
}
int main(int argc, char** argv)
{
glutCreateWindow("simple triangles");
glutDisplayFunc(Render);
glutReshapeFunc(reshape);
init();
glutMainLoop();
}

Answer 1

First of all, you're not calling glutInit(&argc, argv) in main() before all the other GLUT related calls. Second of all, you're not calling glutSwapBuffers() in Render().
Besides that you aren't changing the projection matrix, and thus don't have the same resize function as the one presented in the beginning of the tutorial.
void Resize(int width, int height)
{
glViewport(0, 0, (GLsizei)width, (GLsizei)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f, (GLfloat)width / (GLfloat)height, 1.0f, 1000.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
Changing those things and your code should work.