Triangle and Rectangle in GLUT

Triangle and Rectangle

Source Code:

#include<GL/freeglut.h>

void display(void) {

       glClear(GL_COLOR_BUFFER_BIT);

      

       //draw triangle

       glColor3f(255,255,0);      //(red, green, blue)

       glBegin(GL_POLYGON);

       //A

       glVertex3f(0.0, 10.0, 0.0);

       //B

       glVertex3f(-4.0, 2.0, 0.0);

       //C

       glVertex3f(4.0, 2.0, 0.0);

       glEnd();

       glFlush();

       // draw a rectangle

       glColor3f(255, 0.0, 255); //(red, green, blue)

       glBegin(GL_POLYGON);

      

       // A

       glVertex3f(-4.0, -2.0, 0.0);

       //B

       glVertex3f(4.0, -2.0, 0.0);

       //C

       glVertex3f(4.0, -9.0, 0.0);

       //D

       glVertex3f(-4.0, -9.0, 0.0);

      

       glEnd();

       glFlush();

}

void init(void) {

       // select background color

       glClearColor(0.0, 0.0, 0.0, 0.0); // (red, green, blue, alpha), used by glClear

       // Define world coordinate frame

       glMatrixMode(GL_PROJECTION);

       glLoadIdentity();

       glOrtho(-10.0, 10.0, -10.0, 10.0, -10.0, 10.0); // model in real word units

       // (left, right, bottom, top, near, far)

}

int main(int argc, char** argv) {

       //Step#1 Create and initialize glut windowing system

       glutInit(&argc, argv);

       glutInitWindowSize(600, 400);

       glutInitWindowPosition(100, 100);

       glutCreateWindow("Hello Computer Graphics Students");

       //Step#2 Do Open GL related initializations

       init();

       //Step#3 Register Call back methods or Event Handler methods

       glutDisplayFunc(display);

       //Step#4 Enter in  main loop (an infinite loop listening to registered events and then call their registered methods if any)

       glutMainLoop();

       return 0;

}