In the Previous chapter we have learned how draw a basic line using JOGL. We draw lines by passing a predefined field, Gl_lines to glBegin() method.

This chapter provides examples to draw shapes like triangle, rhombus and a house, using glBegin() method and GL_Lines.

Let us go through a program to draw a triangle using GL_LINES −

import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.GLProfile;
import javax.media.opengl.awt.GLCanvas;

import javax.swing.JFrame;

public class Triangle implements GLEventListener {

   @Override
   public void display(GLAutoDrawable drawable) {
      final GL2 gl = drawable.getGL().getGL2();
      gl.glBegin (GL2.GL_LINES);
   
      //drawing the base
      gl.glBegin (GL2.GL_LINES);
      gl.glVertex3f(-0.50f, -0.50f, 0);
      gl.glVertex3f(0.50f, -0.50f, 0);
      gl.glEnd();
   
      //drawing the right edge
      gl.glBegin (GL2.GL_LINES);
      gl.glVertex3f(0f, 0.50f, 0);
      gl.glVertex3f(-0.50f, -0.50f, 0);
      gl.glEnd();
   
      //drawing the lft edge
      gl.glBegin (GL2.GL_LINES);
      gl.glVertex3f(0f, 0.50f, 0);
      gl.glVertex3f(0.50f, -0.50f, 0);
      gl.glEnd();
      gl.glFlush();
   }
   
   @Override
   public void dispose(GLAutoDrawable arg0) {
      //method body
   }
   
   @Override
   public void init(GLAutoDrawable arg0) {
      // method body
   }
   
   @Override
   public void reshape(GLAutoDrawable arg0, int arg1, int arg2, int arg3, int arg4) {
      // method body
   }
   
   public static void main(String[] args) {
      
      //getting the capabilities object of GL2 profile
      final GLProfile profile = GLProfile.get(GLProfile.GL2);
      GLCapabilities capabilities = new GLCapabilities(profile);
   
      // The canvas
      final GLCanvas glcanvas = new GLCanvas(capabilities);
      Triangle l = new Triangle();
      glcanvas.addGLEventListener(l);
      glcanvas.setSize(400, 400);
   
      //creating frame
      final JFrame frame = new JFrame ("Triangle");
   
      //adding canvas to frame
      frame.getContentPane().add(glcanvas);
          
      frame.setSize(frame.getContentPane().getPreferredSize());
      frame.setVisible(true);
      
   }//end of main
	
}//end of classimport javax.media.opengl.GL2;

If you compile and execute the above program, the following output is generated.
It shows a triangle drawn using GL_LINES of glBegin() method.

Let us go through a program to draw a rhombus using GL_LINES −

import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.GLProfile;
import javax.media.opengl.awt.GLCanvas;

import javax.swing.JFrame;

public class Rhombus implements GLEventListener {

   @Override
   public void display( GLAutoDrawable drawable ) {
      final GL2 gl = drawable.getGL().getGL2();
      
      //edge1  
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( 0.0f,0.75f,0 );
      gl.glVertex3f( -0.75f,0f,0 );
      gl.glEnd();
      
      //edge2
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( -0.75f,0f,0 );
      gl.glVertex3f( 0f,-0.75f, 0 );
      gl.glEnd();
      
      //edge3
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( 0f,-0.75f, 0 );
      gl.glVertex3f( 0.75f,0f, 0 );
      gl.glEnd();
      
      //edge4
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( 0.75f,0f, 0 );
      gl.glVertex3f( 0.0f,0.75f,0 );
      gl.glEnd();
      gl.glFlush();
   }
	
   @Override
   public void dispose( GLAutoDrawable arg0 ) {
      //method body
   }
	
   @Override
   public void init(GLAutoDrawable arg0 ) {
      // method body
   }
	
   @Override
   public void reshape( GLAutoDrawable arg0, int arg1, int arg2, int arg3, int arg4 ) {
      // method body
   }
	
   public static void main( String[] args ) {
	
      //getting the capabilities object of GL2 profile
      final GLProfile profile = GLProfile.get( GLProfile.GL2 );
      GLCapabilities capabilities = new GLCapabilities(profile);
      
      // The canvas
      final GLCanvas glcanvas = new GLCanvas( capabilities );
      Rhombus rhombus = new Rhombus();
      glcanvas.addGLEventListener( rhombus );
      glcanvas.setSize( 400, 400 );
      
      //creating frame
      final JFrame frame = new JFrame ( "Rhombus" );
      
      //adding canvas to frame
      frame.getContentPane().add( glcanvas );
      frame.setSize(frame.getContentPane().getPreferredSize() );
      frame.setVisible( true );
   }
	
}

If you compile and execute the above program, you get the following output. It shows a rhombus generated using GL_LINES of glBegin() method.

Let us go through a program to draw a house using GL_LINES −

import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.GLProfile;
import javax.media.opengl.awt.GLCanvas;

import javax.swing.JFrame;

public class House implements GLEventListener {

   @Override
   public void display( GLAutoDrawable drawable ) {
      final GL2 gl = drawable.getGL().getGL2();
      
      //drawing top
      gl.glBegin ( GL2.GL_LINES );
      gl.glVertex3f( -0.3f, 0.3f, 0 );
      gl.glVertex3f( 0.3f,0.3f, 0 );
      gl.glEnd();
      
      //drawing bottom
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( -0.3f,-0.3f, 0 );
      gl.glVertex3f( 0.3f,-0.3f, 0 );
      gl.glEnd();
      
      //drawing the right edge
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( -0.3f,0.3f, 0 );
      gl.glVertex3f( -0.3f,-0.3f, 0 );
      gl.glEnd();
      
      //drawing the left edge
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( 0.3f,0.3f,0 );
      gl.glVertex3f( 0.3f,-0.3f,0 );
      gl.glEnd();
      
      //building roof
      //building lft dia
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( 0f,0.6f, 0 );
      gl.glVertex3f( -0.3f,0.3f, 0 );
      gl.glEnd();
      
      //building rt dia
      gl.glBegin( GL2.GL_LINES );
      gl.glVertex3f( 0f,0.6f, 0 );
      gl.glVertex3f( 0.3f,0.3f, 0 );
      gl.glEnd();
      
      //building door
      //drawing top
      gl.glBegin ( GL2.GL_LINES );
      gl.glVertex3f( -0.05f, 0.05f, 0 );
      gl.glVertex3f( 0.05f, 0.05f, 0 );
      gl.glEnd();
      
      //drawing the left edge
      gl.glBegin ( GL2.GL_LINES );
      gl.glVertex3f( -0.05f, 0.05f, 0 );
      gl.glVertex3f( -0.05f, -0.3f, 0 );
      gl.glEnd();
      
      //drawing the right edge
      gl.glBegin ( GL2.GL_LINES );
      gl.glVertex3f( 0.05f, 0.05f, 0 );
      gl.glVertex3f( 0.05f, -0.3f, 0 );
      gl.glEnd();
   }
      
   @Override
   public void dispose( GLAutoDrawable arg0 ) {
      //method body
   }
   
   @Override
   public void init( GLAutoDrawable arg0 ) {
      // method body
   }       
   
   @Override
   public void reshape( GLAutoDrawable arg0, int arg1, int arg2, int arg3, int arg4 ) {
      // method body
   }
	
   public static void main( String[] args ) {
   
      //getting the capabilities object of GL2 profile
      final GLProfile profile = GLProfile.get( GLProfile.GL2 );
      GLCapabilities capabilities = new GLCapabilities(profile);
   
      // The canvas
      final GLCanvas glcanvas = new GLCanvas( capabilities );
      House house = new House();
      glcanvas.addGLEventListener( house );
      glcanvas.setSize(400, 400);
   
      //creating frame
      final JFrame frame = new JFrame( "House" );
   
      //adding canvas to frame
      frame.getContentPane().add( glcanvas );
      frame.setSize(frame.getContentPane().getPreferredSize() );
      frame.setVisible( true );
      
   }//end of main
	
}//end of class

If you compile and execute the above program, you get the following output. It shows a house diagram generated using GL_LINES() method.