PROG2.cpp

#include<stdio.h>
#include<GL/glut.h>
int x,y;
int where_to_rotate=0;
float translate_x=0.0,translate_y=0.0,rotate_angle=0.0;
void draw_pixel(float x1,float y1)
{
	glPointSize(5.0);
	glBegin(GL_POINTS);
		glVertex2f(x1,y1);
	glEnd();
}
void triangle(int x,int y)
{
	glColor3f(0.0,1.0,0.0); // set interior color of triangle to green
	glBegin(GL_POLYGON);
		glVertex2f(x,y);
		glVertex2f(x+400,y+400);
		glVertex2f(x+300,y+0);
	glEnd();
	glFlush();
}
void display()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glLoadIdentity();
	glColor3f(1.0,0.0,0.0); //color of point
	draw_pixel(0.0,0.0);
	if(where_to_rotate==1)
	{
		translate_x=0.0;
		translate_y=0.0;
		rotate_angle+=0.9;
	}
	if(where_to_rotate==2)
	{
		translate_x=x;
		translate_y=y;
		rotate_angle+=0.9;
		glColor3f(0.0,0.0,1.0);
		draw_pixel(x,y);
	}
	glTranslatef(translate_x,translate_y,0.0);
	glRotatef(rotate_angle,0.0,0.0,1.0);
	glTranslatef(-translate_x,-translate_y,0.0);
	triangle(translate_x,translate_y);
	glutPostRedisplay();
	glutSwapBuffers();
}
void myInit()
{
	glClearColor(1.0,1.0,1.0,1.0); //background color to white
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(-800.0,800.0,-800.0,800.0);
	glMatrixMode(GL_MODELVIEW);
}
void rotate_menu(int option)
{
	if(option==1)
		where_to_rotate=1;
	if(option==2)
		where_to_rotate=2;
	if(option==3)
		where_to_rotate=3;
	display();
}
int main(int argc,char **argv)
{
	printf("\nEnter fixed points for rotation (x,y) : ");
	scanf("%d%d",&x,&y);
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);
	glutInitWindowSize(800,800);
	glutInitWindowPosition(0,0);
	glutCreateWindow("Rotate Created Triangle");
		myInit();
	glutDisplayFunc(display);
	glutCreateMenu(rotate_menu);
		glutAddMenuEntry("Rotate Around Origin",1);
		glutAddMenuEntry("Rotate Around Fixed Points",2);
		glutAddMenuEntry("Stop Rotation",3);
	glutAttachMenu(GLUT_RIGHT_BUTTON);
	glutMainLoop();
}