rotating-triangle.cpp

#include <GLUT/GLUT.h>
#include<OpenGL/OpenGL.h>

#include<iostream>
//#include<time>
#include<cstdlib>

#include <cmath>
#include <cstdio>


void keyPress(unsigned char key,int x,int y)
{
    
    switch(key)
    {
        case 27:
            exit(0);
            
    }
}

void initRendering()
{
    glEnable(GL_DEPTH_TEST);
}


//Called when the window is resized
void handleResize(int w, int h) {
    //Tell OpenGL how to convert from coordinates to pixel values
    glViewport(0, 0, w, h);
    
    glMatrixMode(GL_PROJECTION); //Switch to setting the camera perspective
    
    //Set the camera perspective
    glLoadIdentity(); //Reset the camera
    gluPerspective(45.0,                  //The camera angle
                   (double)w / (double)h, //The width-to-height ratio
                   1.0,                   //The near z clipping coordinate
                   200.0);                //The far z clipping coordinate
}

float _angle = 30.0f;
float _cameraAngle = 0.0f;


void drawScene()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    
    glMatrixMode(GL_MODELVIEW);
    
    glLoadIdentity();
    
    glPushMatrix(); //Save the transformations performed thus far
    
    glRotatef(_angle, -1.5f, 0.5f, -5.0f); //Rotate about the z-axis
    
    glBegin(GL_TRIANGLES);
    
    glVertex3f(-0.5f, 0.5f, -5.0f);
    glVertex3f(-1.0f, 1.5f, -5.0f);
    glVertex3f(-1.5f, 0.5f, -5.0f);
    
    glEnd();
    glPopMatrix(); //Undo the move to the center of the triangle

    glutSwapBuffers();
}

void update(int value) {
    _angle += 2.0f;
    if (_angle > 360) {
        _angle -= 360;
    }
    
    glutPostRedisplay(); //Tell GLUT that the display has changed
    
    //Tell GLUT to call update again in 25 milliseconds
    glutTimerFunc(25, update, 0);
}

int main(int argc,char** argv)
{
    glutInit(&argc,argv);
    
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
    
    glutInitWindowSize(400,400);
    
    glutCreateWindow("");
    
    initRendering();
    
    glutDisplayFunc(drawScene);
    
    glutKeyboardFunc(keyPress);
    
    glutReshapeFunc(handleResize);
    
    
    glutTimerFunc(25, update, 0); //Add a timer
    
    glutMainLoop();
    
    return(0);
}