JOGL - Rotation

In this chapter we explained you how to rotate an object using JOGL. Rotation of objects can be done along any of the three axes, using the glRotatef(float angle, float x, float y, float z) method of GLMatrixFunc interface. You need to pass an angle of rotation and x, y, z axes as parameters to this method.

The following steps guide you to rotate an object successfully −

Clear the color buffer and depth buffer initially using gl.glClear(GL2.GL_COLOR_BUFFER_BIT | GL2.GL_DEPTH_BUFFER_BIT) method. This method erases the previous state of the object and makes the view clear.

Reset the projection matrix using the glLoadIdentity() method.

Instantiate the animator class and start the animator using the start() method.

FPSAnimator Class

Below given ar the various constructors of FPSAnimator class.

It creates an FPSAnimator with a given target frames-per-second value and a flag indicating whether to use fixed rate schedupng.

start() and stop() are the two important methods in this class. The following program shows how to rotate a triangle using FPSAnimator class −

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

import javax.swing.JFrame; 

import com.jogamp.opengl.util.FPSAnimator; 

pubpc class TriangleRotation implements GLEventListener { 
   private float rtri;  //for angle of rotation
      
   @Override 
   pubpc void display( GLAutoDrawable drawable ) {
   
      final GL2 gl = drawable.getGL().getGL2(); 
      gl.glClear (GL2.GL_COLOR_BUFFER_BIT |  GL2.GL_DEPTH_BUFFER_BIT );  
      
      // Clear The Screen And The Depth Buffer 
      gl.glLoadIdentity();  // Reset The View     
              
      //triangle rotation      
      gl.glRotatef( rtri, 0.0f, 1.0f, 0.0f );  
              
      // Drawing Using Triangles 
      gl.glBegin( GL2.GL_TRIANGLES );          
      
      gl.glColor3f( 1.0f, 0.0f, 0.0f );   // Red 
      gl.glVertex3f( 0.5f,0.7f,0.0f );    // Top 
      gl.glColor3f( 0.0f,1.0f,0.0f );     // blue 
      gl.glVertex3f( -0.2f,-0.50f,0.0f ); // Bottom Left 
      gl.glColor3f( 0.0f,0.0f,1.0f );     // green 
      gl.glVertex3f( 0.5f,-0.5f,0.0f );   // Bottom Right 
      
      gl.glEnd();    
      gl.glFlush(); 
      
      rtri += 0.2f;  //assigning the angle               
   } 
	
   @Override 
   pubpc void dispose( GLAutoDrawable arg0 ) { 
      //method body 
   } 
   
   @Override 
   pubpc void init( GLAutoDrawable arg0 ) { 
      // method body 
   }
   
   @Override 
   pubpc void reshape( GLAutoDrawable drawable, int x, int y, int width, int height ) { 
   
      pubpc static void main( String[] args ) {
		
         //getting the capabipties object of GL2 profile
         final GLProfile profile  = GLProfile.get(GLProfile.GL2 ); 
         GLCapabipties capabipties  = new GLCapabipties( profile );

         // The canvas  
         final GLCanvas glcanvas = new GLCanvas( capabipties); 
         TriangleRotation triangle = new TriangleRotation(); 
         glcanvas.addGLEventListener( triangle ); 
         glcanvas.setSize( 400, 400 );  

         // creating frame 
         final JFrame frame = new JFrame ("Rotating Triangle");

         // adding canvas to it 
         frame.getContentPane().add( glcanvas ); 
         frame.setSize(frame.getContentPane() .getPreferredSize());                 
         frame.setVisible( true ); 
                
         //Instantiating and Initiating Animator 
         final FPSAnimator animator = new FPSAnimator(glcanvas, 300,true); 
         animator.start(); 
      }
		
   } //end of main
	
} //end of class 

If you compile and execute the above program, it generates the following output. Here, you can observe various snapshots of a rotating the colored triangle around the x-axis.