OpenGL Tutorial 2D Moving Car

In this post we are going to learn opengl tutorial on 2D Moving Car. This is very simple tutorial on opengl, which will teach how to make use of simple polygon functions. You can see the final output of below.

We are going to make the 2D Car with simple polygon - triangle, quadrilateral and circle. In this opengl tutorial we are going to use these three simple polygon to create the car. Since we are going to make moving Car, hence first going to define the angle of movement.

/* rotation angle for the triangle. */
float rtri = 0.0f;

/* rotation angle for the quadrilateral. */
float rquad = 0.0f;

Next step is to create a function that will generate the wheel of car.

void drawBall(void) {
        glColor3f(0.0, 1.0, 0.0); //set ball colour
        glTranslatef(ballX,ballY,ballZ); //moving it toward the screen a bit on creation
        //glRotatef(ballX,ballX,ballY,ballZ);
        glutSolidSphere (0.3, 20, 20); //create ball.
        glTranslatef(ballX+1.5,ballY,ballZ); //moving it toward the screen a bit on creation
        glutSolidSphere (0.3, 20, 20); //
        }

Draw Rest part of Car

We are going to draw the rest of the car with the display functions in our opengl tutorial. 

/* The main drawing function. */
void DrawGLScene()
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);        // Clear The Screen And The Depth Buffer
  glLoadIdentity();                // Reset The View

  glTranslatef(rtri,0.0f,-6.0f);        // Move Left 1.5 Units And Into The Screen 6.0
   
  //glRotatef(rtri,1.0f,0.0f,0.0f);        // Rotate The Triangle On The Y axis
  // draw a triangle (in smooth coloring mode)
  glBegin(GL_POLYGON);                // start drawing a polygon
  glColor3f(1.0f,0.0f,0.0f);            // Set The Color To Red
  glVertex3f(-1.0f, 1.0f, 0.0f);        // Top left
  glVertex3f(0.4f, 1.0f, 0.0f);
  
  glVertex3f(1.0f, 0.4f, 0.0f);
  
  glColor3f(0.0f,1.0f,0.0f);            // Set The Color To Green
  glVertex3f( 1.0f,0.0f, 0.0f);        // Bottom Right
  glColor3f(0.0f,0.0f,1.0f);            // Set The Color To Blue
  glVertex3f(-1.0f,0.0f, 0.0f);// Bottom Left    

  //glVertex3f();
  glEnd();                    // we're done with the polygon (smooth color interpolation)
  drawBall();
 
  rtri+=0.005f;                    // Increase The Rotation Variable For The Triangle
  if(rtri>2)
      rtri=-2.0f;
  rquad-=15.0f;                    // Decrease The Rotation Variable For The Quad

  // swap the buffers to display, since double buffering is used.
  glutSwapBuffers();
}

Now you need to have the init functions, window resize function, simple keyboard and main functions. We have included all the function and create the program for this opengl tutorial.  See the full source code for the program given below.

#include     // Header File For The GLUT Library 
#include     // Header File For The OpenGL32 Library
#include     // Header File For The GLu32 Library
//#include      // Header File For sleeping.

/* ASCII code for the escape key. */
#define ESCAPE 27

/* The number of our GLUT window */
int window; 

/* rotation angle for the triangle. */
float rtri = 0.0f;

/* rotation angle for the quadrilateral. */
float rquad = 0.0f;

/* A general OpenGL initialization function.  Sets all of the initial parameters. */
// We call this right after our OpenGL window is created.
void InitGL(int Width, int Height)         
{
  // This Will Clear The Background Color To Black
  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);     
  glClearDepth(1.0);                // Enables Clearing Of The Depth Buffer
  glDepthFunc(GL_LESS);                // The Type Of Depth Test To Do
  glEnable(GL_DEPTH_TEST);            // Enables Depth Testing
  glShadeModel(GL_SMOOTH);            // Enables Smooth Color Shading

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();                // Reset The Projection Matrix

  gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f);  

  glMatrixMode(GL_MODELVIEW);
}

/* The function called when our window is resized (which shouldn't happen, because we're fullscreen) */
void ReSizeGLScene(int Width, int Height)
{
  if (Height==0)                // Prevent A Divide By Zero If The Window Is Too Small
    Height=1;

  glViewport(0, 0, Width, Height);        // Reset The Current Viewport And Perspective Transformation

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();

  gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f);
  glMatrixMode(GL_MODELVIEW);
}

float ballX = -0.5f;
float ballY = 0.0f;
float ballZ = 0.0f;

void drawBall(void) {
        glColor3f(0.0, 1.0, 0.0); //set ball colour
        glTranslatef(ballX,ballY,ballZ); //moving it toward the screen a bit on creation
        //glRotatef(ballX,ballX,ballY,ballZ);
        glutSolidSphere (0.3, 20, 20); //create ball.
        glTranslatef(ballX+1.5,ballY,ballZ); //moving it toward the screen a bit on creation
        glutSolidSphere (0.3, 20, 20); //
        }


/* The main drawing function. */
void DrawGLScene()
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);        // Clear The Screen And The Depth Buffer
  glLoadIdentity();                // Reset The View

  glTranslatef(rtri,0.0f,-6.0f);        // Move Left 1.5 Units And Into The Screen 6.0
   
  //glRotatef(rtri,1.0f,0.0f,0.0f);        // Rotate The Triangle On The Y axis
  // draw a triangle (in smooth coloring mode)
  glBegin(GL_POLYGON);                // start drawing a polygon
  glColor3f(1.0f,0.0f,0.0f);            // Set The Color To Red
  glVertex3f(-1.0f, 1.0f, 0.0f);        // Top left
  glVertex3f(0.4f, 1.0f, 0.0f);
  
  glVertex3f(1.0f, 0.4f, 0.0f);
  
  glColor3f(0.0f,1.0f,0.0f);            // Set The Color To Green
  glVertex3f( 1.0f,0.0f, 0.0f);        // Bottom Right
  glColor3f(0.0f,0.0f,1.0f);            // Set The Color To Blue
  glVertex3f(-1.0f,0.0f, 0.0f);// Bottom Left    

  //glVertex3f();
  glEnd();                    // we're done with the polygon (smooth color interpolation)
  drawBall();
 
  rtri+=0.005f;                    // Increase The Rotation Variable For The Triangle
  if(rtri>2)
      rtri=-2.0f;
  rquad-=15.0f;                    // Decrease The Rotation Variable For The Quad

  // swap the buffers to display, since double buffering is used.
  glutSwapBuffers();
}

/* The function called whenever a key is pressed. */
void keyPressed(unsigned char key, int x, int y) 
{
    /* sleep to avoid thrashing this procedure */
   // usleep(100);

    /* If escape is pressed, kill everything. */
    if (key == ESCAPE) 
    { 
    /* shut down our window */
    glutDestroyWindow(window);
   
    /* exit the program...normal termination. */
    exit(0);                  
    }
}

int main(int argc, char **argv) 
{  
  glutInit(&argc, argv);  

  glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH);  

  /* get a 640 x 480 window */
  glutInitWindowSize(640, 480);  

  /* the window starts at the upper left corner of the screen */
  glutInitWindowPosition(0, 0);  

  /* Open a window */  
  window = glutCreateWindow("Moving Car");  

  /* Register the function to do all our OpenGL drawing. */
  glutDisplayFunc(&DrawGLScene);  

  /* Go fullscreen.  This is as soon as possible. */
  //glutFullScreen();

  /* Even if there are no events, redraw our gl scene. */
  glutIdleFunc(&DrawGLScene);

  /* Register the function called when our window is resized. */
  glutReshapeFunc(&ReSizeGLScene);

  /* Register the function called when the keyboard is pressed. */
  glutKeyboardFunc(&keyPressed);

  /* Initialize our window. */
  InitGL(640, 480);
  
  /* Start Event Processing Engine */  
  glutMainLoop();  

  return 1;
}