JOGL - 著色

本章將向你介紹如何使用 JOGL 為物件應用顏色。若要為物件應用顏色，請使用 GL2 中的 glColor() 方法。下面給出了使用 glColor 方法的語法。

語法

gl.glColorXY(1f,0f,0f); 

其中：

• X 表示使用的顏色數，3（紅色、綠色、藍色）或 4（紅色、綠色、藍色、alpha）。若要獲得不同的顏色組合，請將這些顏色的值作為引數傳遞。必須按順序放置顏色引數。

  示例

  如果你將顏色值傳遞為 (1, 0, 0)，那麼你將得到紅色。類似地，(1, 1, 0) 會給你黃色。

• Y 表示接受 byte(b)、double(d)、float(f)、int(i)、short(s)、ubyte(ub)、uint(ui) 和 ushort(us) 等引數的資料型別。

gl.glColor3f(1f,0f,0f);   //gives us red          
gl.glColor3f(0f,1f,0f);   //gives us green            
gl.glColor3f(0f,0f,1f);   //gives us blue

對於三角形，你可以為每個頂點應用不同的顏色。

我們來看一個為三角形應用顏色的程式 −

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 TriangleColor implements GLEventListener { 

   @Override 
   public void display( GLAutoDrawable drawable ) { 
   
      final GL2 gl = drawable.getGL().getGL2(); 
      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 );     // green 
      gl.glVertex3f( -0.2f,-0.50f,0.0f ); // Bottom Left 
		
      gl.glColor3f( 0.0f,0.0f,1.0f );     // blue 
      gl.glVertex3f( 0.5f,-0.5f,0.0f );   // Bottom Right 
		
      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 ); 
      TriangleColor triangle = new TriangleColor(); 
      glcanvas.addGLEventListener( triangle ); 
      glcanvas.setSize( 400, 400 );   
      
      //creating frame 
      final JFrame frame = new JFrame (" Colored Triangle"); 
          
      //adding canvas to it 
      frame.getContentPane().add( glcanvas ); 
      frame.setSize( frame.getContentPane().getPreferredSize()); 
      frame.setVisible( true );   
      
   } //end of main
	
} //end of class 

當你編譯並執行以上程式時，你將得到以下彩色三角形 −

為多邊形應用顏色

我們來看一個為多邊形應用顏色的程式 −

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 PolygonColor implements GLEventListener { 

   @Override 
   public void display( GLAutoDrawable drawable ) { 
   
      final GL2 gl = drawable.getGL().getGL2(); 
      gl.glColor3f( 1f,0f,0f ); //applying red  
  
      gl.glBegin( GL2.GL_POLYGON ); 
      
      gl.glVertex3f( 0f,0.5f,0f  ); 
      gl.glVertex3f( -0.5f,0.2f,0f ); 
      gl.glVertex3f( -0.5f,-0.2f,0f ); 
      gl.glVertex3f( 0f,-0.5f,0f ); 
      gl.glVertex3f( 0f,0.5f,0f ); 
      gl.glVertex3f( 0.5f,0.2f,0f ); 
      gl.glVertex3f( 0.5f,-0.2f,0f ); 
      gl.glVertex3f( 0f,-0.5f,0f ); 
      
      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 ); 
      PolygonColor polygon = new PolygonColor(); 
      glcanvas.addGLEventListener( polygon ); 
      glcanvas.setSize( 400, 400 ); 
      
      //creating frame 
      final JFrame frame = new JFrame ( "Colored Polygon" ); 
      
      //adding canvas to frame 
      frame.getContentPane().add( glcanvas ); 
      frame.setSize(frame.getContentPane().getPreferredSize() ); 
      frame.setVisible( true );    
      
   } //end of main 
	
 } //end of class 

當你編譯並執行以上程式時，你將得到以下彩色多邊形 −