JOGL - Triangolo 3D

Nel capitolo precedente abbiamo visto come disegnare forme 3d, questo capitolo ti insegna come disegnare un triangolo 3d e ruotarlo.

Di seguito è riportato il programma per disegnare un triangolo 3d e ruotarlo.

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.media.opengl.glu.GLU;

import javax.swing.JFrame;

import com.jogamp.opengl.util.FPSAnimator;

public class Triangle3d implements GLEventListener {

   private GLU glu = new GLU();
   private float rtri = 0.0f;
      
   @Override
   public void display(GLAutoDrawable drawable) {
      final GL2 gl = drawable.getGL().getGL2();

      // Clear The Screen And The Depth Buffer
      gl.glClear( GL2.GL_COLOR_BUFFER_BIT | GL2.GL_DEPTH_BUFFER_BIT );
      gl.glLoadIdentity(); // Reset The View
      gl.glTranslatef( -0.5f, 0.0f, -6.0f ); // Move the triangle
      gl.glRotatef( rtri, 0.0f, 1.0f, 0.0f );
      gl.glBegin( GL2.GL_TRIANGLES ); 
        
      //drawing triangle in all dimensions
      // Front
      gl.glColor3f( 1.0f, 0.0f, 0.0f ); // Red
      gl.glVertex3f( 1.0f, 2.0f, 0.0f ); // Top Of Triangle (Front)
		
      gl.glColor3f( 0.0f, 1.0f, 0.0f ); // Green
      gl.glVertex3f( -1.0f, -1.0f, 1.0f ); // Left Of Triangle (Front)
		
      gl.glColor3f( 0.0f, 0.0f, 1.0f ); // Blue
      gl.glVertex3f( 1.0f, -1.0f, 1.0f ); // Right Of Triangle (Front)
        
      // Right
      gl.glColor3f( 1.0f, 0.0f, 0.0f ); // Red
      gl.glVertex3f( 1.0f, 2.0f, 0.0f ); // Top Of Triangle (Right)
		
      gl.glColor3f( 0.0f, 0.0f, 1.0f ); // Blue
      gl.glVertex3f( 1.0f, -1.0f, 1.0f ); // Left Of Triangle (Right)
		
      gl.glColor3f( 0.0f, 1.0f, 0.0f ); // Green
      gl.glVertex3f( 1.0f, -1.0f, -1.0f ); // Right Of Triangle (Right)
        
      // Left
      gl.glColor3f( 1.0f, 0.0f, 0.0f ); // Red
      gl.glVertex3f( 1.0f, 2.0f, 0.0f ); // Top Of Triangle (Back)
		
      gl.glColor3f( 0.0f, 1.0f, 0.0f ); // Green
      gl.glVertex3f( 1.0f, -1.0f, -1.0f ); // Left Of Triangle (Back)
		
      gl.glColor3f( 0.0f, 0.0f, 1.0f ); // Blue
      gl.glVertex3f( -1.0f, -1.0f, -1.0f ); // Right Of Triangle (Back)
        
      //left
      gl.glColor3f( 0.0f, 1.0f, 0.0f ); // Red
      gl.glVertex3f( 1.0f, 2.0f, 0.0f ); // Top Of Triangle (Left)
		
      gl.glColor3f( 0.0f, 0.0f, 1.0f ); // Blue
      gl.glVertex3f( -1.0f, -1.0f, -1.0f ); // Left Of Triangle (Left)
		
      gl.glColor3f( 0.0f, 1.0f, 0.0f ); // Green
      gl.glVertex3f( -1.0f, -1.0f, 1.0f ); // Right Of Triangle (Left)
		
      gl.glEnd(); // Done Drawing 3d triangle (Pyramid)
      gl.glFlush();
      rtri += 0.2f;
   }
   
   @Override
   public void dispose( GLAutoDrawable drawable ) {
      //method body
   }
   
   @Override
   public void init( GLAutoDrawable drawable ) {
      //method body
   }
   
   @Override
   public void reshape( GLAutoDrawable drawable, int x, int y, int width, int height ) {
	
      // TODO Auto-generated method stub
      final GL2 gl = drawable.getGL().getGL2();
      if(height lt;=;)
         height = 1;
			
      final float h = ( float ) width / ( float ) height;
      gl.glViewport( 0, 0, width, height );
      gl.glMatrixMode( GL2.GL_PROJECTION );
      gl.glLoadIdentity();
		
      glu.gluPerspective( 45.0f, h, 1.0, 20.0 );
      gl.glMatrixMode( GL2.GL_MODELVIEW );
      gl.glLoadIdentity();
   }
   
   public static void main( String[] args ) {
   
      // TODO Auto-generated method stub
      final GLProfile profile = GLProfile.get( GLProfile.GL2 );
      GLCapabilities capabilities = new GLCapabilities( profile );
         
      // The canvas
      final GLCanvas glcanvas = new GLCanvas( capabilities );
      Triangle3d triangle = new Triangle3d();
		
      glcanvas.addGLEventListener( triangle );
      glcanvas.setSize( 400, 400 );
		
      final JFrame frame = new JFrame ( "3d Triangle (shallow)" );
		
      frame.getContentPane().add( glcanvas );
      frame.setSize( frame.getContentPane().getPreferredSize() );
      frame.setVisible( true );
		
      final FPSAnimator animator = new FPSAnimator(glcanvas,300,true);
      animator.start();
   }
	
}

Quando compili ed esegui il programma precedente, viene generato il seguente output. Qui, hai le istantanee del triangolo 3D rotante. Poiché questo programma non include il test di profondità, il triangolo viene generato vuoto.

Per rendere il triangolo solido, è necessario abilitare il test di profondità utilizzando glEnable(GL_DEPTH_TEST). Abilitando il buffer di profondità si ottiene una schermata vuota. Questo può essere cancellato cancellando il colore usandoglClear(GL_COLOR_BUFFERBIT | GL_DEPTH_BUFFER_BIT)metodo. Per abilitare il test di profondità nel metodo init () o nelglDisplay() metodo, scrivi il codice seguente -

public void init(GLAutoDrawable drawable) {
   final GL2 gl = drawable.getGL().getGL2();
	
   gl.glShadeModel(GL2.GL_SMOOTH);
   gl.glClearColor(0f, 0f, 0f, 0f);
   gl.glClearDepth(1.0f);
   gl.glEnable(GL2.GL_DEPTH_TEST);
   gl.glDepthFunc(GL2.GL_LEQUAL);
   gl.glHint(GL2.GL_PERSPECTIVE_CORRECTION_HINT, GL2.GL_NICEST);
 }

Di seguito viene fornito il programma per disegnare un triangolo 3D con test di profondità.

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.media.opengl.glu.GLU;

import javax.swing.JFrame;

import com.jogamp.opengl.util.FPSAnimator;

public class Triangledepthtest implements GLEventListener {

   private GLU glu = new GLU();
   private float rtri = 0.0f; 
	
   @Override
   public void display( GLAutoDrawable drawable ) {
	
      final GL2 gl = drawable.getGL().getGL2();
		
      gl.glShadeModel( GL2.GL_SMOOTH );
      gl.glClearColor( 0f, 0f, 0f, 0f );
      gl.glClearDepth( 1.0f );
      gl.glEnable( GL2.GL_DEPTH_TEST );
      gl.glDepthFunc( GL2.GL_LEQUAL );
      gl.glHint(GL2.GL_PERSPECTIVE_CORRECTION_HINT, GL2.GL_NICEST);

      // Clear The Screen And The Depth Buffer
      gl.glClear(GL2.GL_COLOR_BUFFER_BIT | GL2.GL_DEPTH_BUFFER_BIT); 
      gl.glLoadIdentity(); // Reset The View
      gl.glTranslatef( -0.5f,0.0f,-6.0f ); // Move the triangle
      gl.glRotatef( rtri, 0.0f, 1.0f, 0.0f );
      gl.glBegin( GL2.GL_TRIANGLES ); 

      //drawing triangle in all dimensions
      //front
      gl.glColor3f( 1.0f, 0.0f, 0.0f ); // Red
      gl.glVertex3f( 1.0f, 2.0f, 0.0f ); // Top
		
      gl.glColor3f( 0.0f, 1.0f, 0.0f ); // Green
      gl.glVertex3f( -1.0f, -1.0f, 1.0f ); // Left
		
      gl.glColor3f( 0.0f, 0.0f, 1.0f ); // Blue
      gl.glVertex3f( 1.0f, -1.0f, 1.0f ); // Right)

      //right
      gl.glColor3f( 1.0f, 0.0f, 0.0f );
      gl.glVertex3f( 1.0f, 2.0f, 0.0f ); // Top
		
      gl.glColor3f( 0.0f, 0.0f, 1.0f );
      gl.glVertex3f( 1.0f, -1.0f, 1.0f ); // Left
		
      gl.glColor3f( 0.0f, 1.0f, 0.0f );
      gl.glVertex3f( 1.0f, -1.0f, -1.0f ); // Right

      //left
      gl.glColor3f( 1.0f, 0.0f, 0.0f );
      gl.glVertex3f( 1.0f, 2.0f, 0.0f ); // Top
		
      gl.glColor3f( 0.0f, 1.0f, 0.0f );
      gl.glVertex3f( 1.0f, -1.0f, -1.0f ); // Left 
		
      gl.glColor3f( 0.0f, 0.0f, 1.0f );
      gl.glVertex3f( -1.0f, -1.0f, -1.0f ); // Right 

      //top
      gl.glColor3f( 0.0f, 1.0f, 0.0f );
      gl.glVertex3f( 1.0f, 2.0f, 0.0f ); // Top
		
      gl.glColor3f( 0.0f, 0.0f, 1.0f );
      gl.glVertex3f( -1.0f, -1.0f, -1.0f ); // Left
		
      gl.glColor3f( 0.0f, 1.0f, 0.0f );
      gl.glVertex3f( -1.0f, -1.0f, 1.0f ); // Right
		
      gl.glEnd(); // Done Drawing 3d triangle (Pyramid)

      gl.glFlush();
      rtri += 0.2f;
   }
      
   @Override
   public void dispose( GLAutoDrawable drawable ) {
   }
   
   @Override
   public void init( GLAutoDrawable drawable ) {
	
      final GL2 gl = drawable.getGL().getGL2();
		
      gl.glShadeModel( GL2.GL_SMOOTH );
      gl.glClearColor( 0f, 0f, 0f, 0f );
      gl.glClearDepth( 1.0f );
      gl.glEnable( GL2.GL_DEPTH_TEST );
      gl.glDepthFunc( GL2.GL_LEQUAL );
      gl.glHint(GL2.GL_PERSPECTIVE_CORRECTION_HINT, GL2.GL_NICEST );
   }
   
   @Override
   public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height ) {
	
      // TODO Auto-generated method stub
      final GL2 gl = drawable.getGL().getGL2();
      if( height <= 0 ) 
         height = 1;
			
      final float h = ( float ) width / ( float ) height;
      gl.glViewport( 0, 0, width, height );
      gl.glMatrixMode( GL2.GL_PROJECTION );
      gl.glLoadIdentity();
		
      glu.gluPerspective( 45.0f, h, 1.0, 20.0 );
      gl.glMatrixMode( GL2.GL_MODELVIEW );
      gl.glLoadIdentity();
   }
      
   public static void main( String[] args ) {
	
      // TODO Auto-generated method stub
      final GLProfile profile = GLProfile.get( GLProfile.GL2 );
      GLCapabilities capabilities = new GLCapabilities( profile );
		
      // The canvas
      final GLCanvas glcanvas = new GLCanvas( capabilities );
      Triangledepthtest triangledepthtest = new Triangledepthtest();
		
      glcanvas.addGLEventListener( triangledepthtest );
      glcanvas.setSize( 400, 400 );
		
      final JFrame frame = new JFrame ( "3d Triangle (solid)" );
      frame.getContentPane().add(glcanvas);
      frame.setSize( frame.getContentPane().getPreferredSize() );
      frame.setVisible( true );
      final FPSAnimator animator = new FPSAnimator( glcanvas, 300,true);
		
      animator.start();
   }
	
}

Quando compili ed esegui il programma precedente, viene generato il seguente output.

Qui puoi vedere le istantanee di un triangolo 3D rotante. Poiché questo programma include codice per il test di profondità, il triangolo viene generato solido.