25. OpenGL Vertex Coloring

//So anyway, I did this with a normal quad
//but it does work with any shape you choose
//Here it is:
//I have started my quad.
//I then set the color red for the first vertex.
//I then draw that vertex.
//The next is green.
//Then blue.
//And finally white.

//glBegin(GL_QUADS);
//glColor3f(1,0,0);
//glVertex3f(-0.5, -0.5, 0.0);
//glColor3f(0,1,0);
//glVertex3f(-0.5, 0.5, 0.0);
//glColor3f(0,0,1);
//glVertex3f(0.5, 0.5, 0.0);
//glColor3f(1,1,1);
//glVertex3f(0.5, -0.5, 0.0);
//glEnd();

//Just remember to call each vertex after you call the color
//for this to work.

#include <GL/gl.h>
#include <GL/glut.h>

void square (void) {
    glBegin(GL_QUADS);
    glColor3f(1,0,0); //red
    glVertex3f(–0.5, –0.5, 0.0);
    glColor3f(0,1,0); //green
    glVertex3f(–0.5, 0.5, 0.0);
    glColor3f(0,0,1); //blue
    glVertex3f(0.5, 0.5, 0.0);
    glColor3f(1,1,1); //white
    glVertex3f(0.5, –0.5, 0.0);
    glEnd();
}

void display (void) {
    glClearColor (0.0,0.0,0.0,1.0);
    glClear (GL_COLOR_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(0,0,–1);
    square();
    glFlush();
}

void reshape (int w, int h) {
    glViewport (0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode (GL_PROJECTION);
    glLoadIdentity ();
    gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
    glMatrixMode (GL_MODELVIEW);
}

int main (int argc, char **argv) {
    glutInit (&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE);
    glutInitWindowSize (500, 500);
    glutInitWindowPosition (100, 100);
    glutCreateWindow (“A basic OpenGL Window“);
    glutDisplayFunc (display);
    glutReshapeFunc (reshape);
    glutMainLoop ();
    return 0;
}