Drawing with GL_Lines

在上一章中，我们学习了如何使用JOGL绘制基本线。 我们通过将预定义字段Gl_lines给glBegin()方法来绘制线条。

本章提供了使用glBegin（）方法和GL_Lines绘制三角形，菱形和房屋等形状的示例。

让我们通过一个程序来使用GL_LINES绘制一个三角形 -

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;

如果编译并执行上述程序，则会生成以下输出。 它显示了使用glBegin()方法的GL_LINES glBegin()的三角形。

让我们通过一个使用GL_LINES绘制菱形的程序 -

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 );
   }
}

如果编译并执行上述程序，则会得到以下输出。 它显示了使用glBegin()方法的GL_LINES生成的菱形。

让我们通过一个程序来使用GL_LINES画一个房子 -

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

如果编译并执行上述程序，则会得到以下输出。 它显示了使用GL_LINES（）方法生成的房屋图。