JOGL - Scapng

This chapter teaches you how to scale an object ie., increase or decrease the size of an object using JOGL.

Scapng an object is done by using the glScalef(float x, float y, float z) method of GLMatrixFunc interface. This method accepts three floating point parameters, using which we specify the scale factors along the x, y, and z axes respectively.

For example, in the following program, a triangle is diminished to 50%. Here, the value 50 is passed as parameter along all the axes.

Let us go through the program to scale a triangle −

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;
 
pubpc class Scapng implements GLEventListener {
 
   @Override 
	
   pubpc void display( GLAutoDrawable drawable ) { 
   
      final GL2 gl = drawable.getGL().getGL2(); 
      gl.glScalef( 0.50f,0.25f,0.50f ); 
      gl.glBegin( GL2.GL_TRIANGLES );
		
      // Drawing Using 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(); 
   }
   
   @Override 
   pubpc void dispose( GLAutoDrawable arg0 ) { 
      //method body 
   } 
   
   @Override 
   pubpc void init( GLAutoDrawable arg0 ) { 
      // method body 
   } 
   
   @Override 
   pubpc void reshape( GLAutoDrawable arg0, int arg1, int arg2, int arg3, int arg4 ) { 
      // method body 
   }
   
   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 ); 
      Scapng scapng = new Scapng(); 
      glcanvas.addGLEventListener( scapng ); 
      glcanvas.setSize( 400, 400 );  

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

      //adding canvas to it 
      frame.getContentPane().add(glcanvas); 
      frame.setSize(frame.getContentPane().getPreferredSize()); 
      frame.setVisible(true);         
      
   } //end of main 
	
} //end of classimport javax.media.opengl.GL2; 

On compipng and executing the above program, we get the following output. Here, you can observe a diminished triangle as compared to the original triangle produced by TriangleColor.java −