This document contains code examples demonstrating the use of OpenGL functions to draw points and lines. The first example draws two points with different colors. The second draws four points with varying sizes and colors. The third draws two red and green lines. The fourth draws a cross shape using four colored lines. All examples initialize an OpenGL window, clear the buffer, set point/line sizes, draw with GL_POINTS or GL_LINES, and enter the main loop.

1. Gl_point
Two points:
#include<GL/glut.h>
void display()
{
glClear(GL_COLOR_BUFFER_BIT);
glClearColor(0.0f,0.0f,0.0f,0.0f);
glPointSize(10.0f);
glBegin(GL_POINTS);
glColor3f(1.0,1.0,0.0);
glVertex2f(0.0f,0.0f);
glVertex2f(0.2f,0.5f);
glEnd();
glFlush();
}
void main(intargc,char**argv)
{
glutInit(&argc,argv);
glutInitWindowSize(420,320);
glutInitWindowPosition(50,50);
glutCreateWindow("GL_POINTS Example");
glutDisplayFunc(display);
glutMainLoop();
}

2. Four Points:
#include<GL/glut.h>
void display()
{
glClear(GL_COLOR_BUFFER_BIT);
glClearColor(0.0f,0.0f,0.0f,0.0f);
glPointSize(10.0f);
glPointSize(30.0f);
glBegin(GL_POINTS);
glColor3f(1.0,0.0,0.0);
glVertex2f(0.0f,0.2f);
glColor3f(1.0,0.0,1.0);
glVertex2f(0.0f,0.5f);
glPointSize(60.0f);
glBegin(GL_POINTS);
glColor3f(0.0,1.0,0.0);
glVertex2f(0.5f,0.2f);
glColor3f(0.0,0.0,1.0);
glVertex2f(0.5f,0.5f);
glEnd();
glFlush();
}
void main(intargc,char**argv)
{
glutInit(&argc,argv);
glutInitWindowSize(420,320);
glutInitWindowPosition(50,50);
glutCreateWindow("GL_POINTS Example");
glutDisplayFunc(display);
glutMainLoop();
}

3. GL_LINES
#include<GL/glut.h>
void display(){
glClear(GL_COLOR_BUFFER_BIT);
glClearColor(0.0f,0.0f,0.0f,0.0f);
glPointSize(100.0f);
glBegin(GL_LINES);
glColor3f(1.0,0.0,0.0);
glVertex2f(0.0f,0.0f);
glVertex2f(0.7f,0.5f);
glPointSize(100.0f);
glBegin(GL_LINES);
glColor3f(0.0,1.0,0.0);
glVertex2f(-0.2f,0.0f);
glVertex2f(-0.7f,0.5f);
glEnd();
glFlush();
}
void main(intargc,char**argv){
glutInit(&argc,argv);
glutInitWindowSize(420,320);
glutInitWindowPosition(50,50);
glutCreateWindow("GL_LINES Example");
glutDisplayFunc(display);
glutMainLoop();
}

4. #include<GL/glut.h>
void display(){
glClear(GL_COLOR_BUFFER_BIT);
glClearColor(0.0f,0.0f,0.0f,0.0f);
glPointSize(100.0f);
glBegin(GL_LINES);
glColor3f(1.0,0.0,0.0);
glVertex2f(0.5f,0.5f);
glVertex2f(-0.5f,0.5f);
glPointSize(100.0f);
glBegin(GL_LINES);
glColor3f(0.0,0.0,1.0);
glVertex2f(-0.5f,0.5f);
glVertex2f(0.5f,-0.5f);
glPointSize(100.0f);
glBegin(GL_LINES);
glColor3f(1.0,1.0,1.0);
glVertex2f(0.5f,-0.5f);
glVertex2f(-0.5f,-0.5f);
glPointSize(100.0f);

5. glBegin(GL_LINES);
glColor3f(1.0,0.0,1.0);
glVertex2f(-0.5f,-0.5f);
glVertex2f(0.5f,0.5f);
glEnd();
glFlush();
}
void main(intargc,char**argv){
glutInit(&argc,argv);
glutInitWindowSize(420,320);
glutInitWindowPosition(50,50);
glutCreateWindow("GL_LINES Example");
glutDisplayFunc(display);
glutMainLoop();
}